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VITEK 2 AST-Gram Negative Cefazolin is designed for antimicrobial susceptibility testing of Gram-negative bacilli and is intended for use with the VITEK 2 Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents.

VITEK 2 AST-Gram Negative Cefazolin (≤1-≥32 µg/mL) is a quantitative test. Testing is indicated for Enterobacterales (from infections other than uncomplicated UTI) as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC).

VITEK 2 AST-Gram Negative Cefazolin (≤1-≥32 µg/mL) has demonstrated acceptable performance with the following organisms:

Enterobacterales (Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter koseri)

The VITEK 2 Gram Negative Susceptibility Card is intended for use with the VITEK 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of clinically significant aerobic Gram- negative bacilli to antimicrobial agents when used as instructed.

The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh (1) and Gerlach (2). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique (3).

Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 – 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

VITEK® 2 AST-GN Cefazolin has the following concentrations in the card: 1, 2, and 8 (equivalent standard method concentration by efficacy in µg/mL).

The provided text describes the acceptance criteria and a study proving the device meets these criteria for the VITEK 2 AST-Gram Negative Cefazolin antimicrobial susceptibility testing system.

Here's a breakdown of the requested information:

1. Table of Acceptance Criteria and Reported Device Performance

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The BD Phoenix™ Automated Microbiology System is intended for in vitro quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most Gram-negative aerobic and facultative anaerobic bacteria isolates from pure culture for Enterobacterales and Non-Enterobacterales and most Gram-positive bacteria isolates from pure culture belonging to the genera Staphylococcus, Enterococcus, and Streptococcus.

This premarket notification is for the BD Phoenix Automated Microbiology System with Imipenem-relebactam at a concentration of 0.0625/4-16/4 µg/mL. Testing is indicated for Acinetobacter calcoaceticus-baumannii complex, Enterobacterales, and Pseudomonas aeruginosa, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC).

The BD Phoenix Automated Microbiology System - GN Imipenem-relebactam (0.0625/4 - 16/4 µg/mL) has demonstrated acceptable performance with the following organisms:

• Acinetobacter calcoaceticus-baumannii complex
• Enterobacterales (Citrobacter amalonaticus, Citrobacter braakii, Citrobacter farmeri, Citrobacter freundii, Citrobacter koseri, Citrobacter youngae, Enterobacter cloacae, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia marcescens)
• Pseudomonas aeruginosa

The Phoenix AST method is a broth-based microdilution test. The Phoenix panel is a sealed and self-inoculating molded polystyrene tray with 136 micro-wells containing dried reagents. The ID/AST combination panel includes an ID side (51 wells) with dried substrates for bacterial identification and an AST side (85 wells). The AST panel contains a wide range of two-fold doubling dilution concentrations of antimicrobial agents and growth and fluorescent controls at appropriate well locations. The AST panel does not include wells for isolate identification.

The Phoenix System utilizes a redox indicator for the detection of organism growth in the presence of an antimicrobial agent. The organism to be tested must be a pure culture and be preliminarily identified as Gram-positive or Gram-negative. Colonies are then suspended in ID broth and equated to a 0.5 McFarland suspension using a nephelometer device. A further dilution is made into AST broth (a cation-adjusted formulation of Mueller-Hinton broth containing 0.010% Tween 80), to which the redox-buffered oxidation-reduction AST indicator solution is added producing a blue color in the wells. The concentration of organisms in the final AST broth suspension is approximately 5 X 10^5 CFU/mL.

The Phoenix AST Broth is poured into the inoculation port of the AST panel and the inoculum flows into the panel, filling panel wells. Polyethylene caps are applied to seal the inoculation ports. An air admittance port is located in the panel lid to ensure adequate oxygen tension in the panel for the duration of the test. Inoculated panels are barcode scanned and loaded into the BD Phoenix Automated Microbiology System instrument where panels are continuously incubated at 35 °C ± 1 °C.

Continuous measurements of changes to the indicator as well as bacterial turbidity are used in the determination of bacterial growth. The instrument takes readings every 20 minutes. Organisms growing in the presence of a given antimicrobial agent reduce the indicator (changing it to a pink color). This signals organism growth and resistance to that antimicrobial agent. Organisms killed or inhibited by the antimicrobial agent do not cause reduction of the indicator and therefore do not produce a color change. The Phoenix instrument reads and records the results of the antimicrobial tests contained in the panel and interprets the reactions (based on the organism identification) to give a minimal inhibitory concentration (MIC) value and category interpretations (susceptible, intermediate, resistant, or not susceptible). AST results are available within 16 hours. This is an auto read result; no manual readings are possible with this system.

Additional comments concerning specific organism/antimicrobial combinations are provided from the software-driven expert system (BDXpert), using rules derived from CLSI documentation and/or the FDA-approved drug labeling.

The provided FDA 510(k) clearance letter describes the acceptance criteria and the study that proves the BD Phoenix™ Automated Microbiology System - GN Imipenem-relebactam (0.0625/4 - 16/4 µg/mL) device meets those criteria for Antimicrobial Susceptibility Testing (AST).

Here's a breakdown of the requested information:

1. Table of Acceptance Criteria and Reported Device Performance

The core acceptance criteria for AST devices are related to Essential Agreement (EA) and Category Agreement (CA) with a reference method. The study aims to demonstrate that the device's performance is substantially equivalent to the established reference method.

Note: The document mentions "The performance of the BD Phoenix Imipenem-relebactam met the combined acceptance criteria for all tested organisms, with overall EA and CA rates greater than 90%." This implicitly sets the 90% for EA and CA as the acceptance threshold.

2. Sample Size Used for the Test Set and Data Provenance

• Clinical Isolates (Test Set):

  • Total: 1,111 isolates (862 fresh, 249 stock)
  • Organisms:
    • Acinetobacter baumannii/calcoaceticus complex (83 isolates)
    • Citrobacter freundii (21 isolates)
    • Citrobacter species (9 isolates)
    • Citrobacter koseri (26 isolates)
    • Enterobacter cloacae (60 isolates)
    • Escherichia coli (359 isolates)
    • Klebsiella aerogenes (58 isolates)
    • Klebsiella oxytoca (47 isolates)
    • Klebsiella pneumoniae (198 isolates)
    • Pseudomonas aeruginosa (176 isolates)
    • Serratia marcescens (74 isolates)
  • Provenance: Conducted at three U.S. clinical sites. Data consists of fresh and stock isolates, implying a mix of retrospective (stock) and prospective (fresh) collection.

• Challenge Isolates (Test Set):

  • Total: 85 isolates (these are specific strains with known resistance mechanisms)
  • Organisms:
    • Acinetobacter baumannii (7 isolates)
    • Citrobacter freundii (2 isolates)
    • Citrobacter koseri (2 isolates)
    • Enterobacter cloacae (12 isolates)
    • Escherichia coli (19 isolates)
    • Klebsiella aerogenes (4 isolates)
    • Klebsiella pneumoniae (24 isolates)
    • Pseudomonas aeruginosa (15 isolates)
  • Provenance: Tested at "each study site" (implying the same three U.S. clinical sites as for clinical isolates). These are typically retrospective isolates chosen to challenge the system.

• Reproducibility Isolates:

  • Total: 15 on-scale isolates (tested in triplicate over three days at three sites, for 405 data points).
  • Organisms: Enterobacter cloacae (2), Escherichia coli (5), Klebsiella aerogenes (1), Klebsiella pneumoniae (3) and Pseudomonas aeruginosa (4).
  • Provenance: Conducted at three clinical sites (for manual method) and three internal BD sites (for Phoenix AP instrument).

3. Number of Experts Used to Establish Ground Truth and Qualifications

This type of medical device (automated microbiology system for AST) does not typically involve human experts to establish "ground truth" in the same way an imaging AI might.

• Ground Truth Establishment: The ground truth for antimicrobial susceptibility testing is established by a reference method, specifically the CLSI frozen broth microdilution reference panel, prepared according to CLSI M07 guidelines. This is a standardized, laboratory-based method, not dependent on expert visual interpretation.
• No "experts" in the human-reader sense are described as establishing ground truth for the test set. The expertise lies in adherence to CLSI standards and methodologies.

4. Adjudication Method for the Test Set

• No human adjudication method (e.g., 2+1, 3+1) is mentioned or applicable for this type of device.
• The comparison is directly between the result from the BD Phoenix system and the CLSI frozen broth microdilution reference panel. Discrepancies are categorized as minor, major, or very major based on established AST definitions (Essential Agreement and Category Agreement).

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

• No, an MRMC study was NOT done. This type of study is relevant for diagnostic imaging interpretation devices where human reader performance is a key metric. For an automated microbiology system, the comparison is to a "gold standard" laboratory method (CLSI microdilution), not to human interpretation or human improvement with AI assistance.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

• Yes, this is essentially a standalone (algorithm only) performance study. The BD Phoenix system is an automated device that reads and interprets the results without human subjective input in the interpretative step. The "human-in-the-loop" aspects are limited to initial inoculum preparation (though automated options are also available and validated) and loading the panel, not interpreting the results. The comparison is the device's output (MIC and category) against the reference method.

7. The Type of Ground Truth Used

• The ground truth used is the CLSI frozen broth microdilution reference panel, which serves as the gold standard reference method for antimicrobial susceptibility testing.

8. The Sample Size for the Training Set

• The document does not explicitly state a separate "training set" sample size. For this type of automated system, which uses a growth-based detection principle rather than a machine learning model trained on large datasets of examples, the concept of a distinct "training set" in the modern AI sense is typically not applicable.
• The system's "training" or development would involve extensive internal R&D, algorithm refinement, and validation using proprietary data over time, which precedes a 510(k) submission. The data provided in the 510(k) is for the validation/test set to demonstrate performance.

9. How the Ground Truth for the Training Set Was Established

• As a conventional, growth-based automated system rather than a machine learning device, there isn't a "training set" with ground truth established in the sense of human labeling or annotation.
• The system operates based on predefined biochemical reactions and growth kinetics, and its algorithms are built upon established microbiological principles and CLSI guidelines. Any internal development and testing would likewise use CLSI reference methods to establish expected outcomes for algorithm development and calibration.

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The VITEK® COMPACT PRO is intended for the automated quantitative and/or qualitative antimicrobial susceptibility testing of isolated colonies for most clinically significant aerobic Gram-negative bacilli, Staphylococcus spp., Enterococcus spp., Streptococcus spp., and yeast.

The VITEK® COMPACT PRO is also intended for the automated identification of most clinically significant anaerobic organisms and Corynebacterium species, fermenting and nonfermenting Gram-negative bacilli, Gram-positive organisms, fastidious organisms, and yeasts and yeast-like organisms.

The VITEK® COMPACT PRO instrument is an automated instrument designed for use in low-to medium-range applications in both Clinical and Industry laboratories. The instrument performs sample well filling, incubation, and optical readings. The VITEK® COMPACT PRO instrument is a two-step automated instrument for:

• Hydrating reagents with sample inoculum
• Pre-processing cards, incubating cards, and continuous reading for growth

The VITEK® 2 Systems Software receives the instrument optical readings and performs analysis. The instrument then ejects the completed reagent card into the waste area for disposal.

The system includes a VITEK® COMPACT PRO instrument with an internal computer, monitor, keyboard, mouse, handheld barcode scanner, and USB hub. The software provided with the internal computer includes analysis and limited data management programs. A bidirectional computer interface (BCI) may transfer results automatically to the user's laboratory information system (LIS).

A Quality Control System is available to track the quality control results of the test cards. The Advanced Expert System™ (Clinical Use) is available to provide online, systematic validation of results and interpretation of resistant phenotypes found during susceptibility testing.

The provided text describes the regulatory clearance of a medical device, the VITEK® COMPACT PRO, and its performance evaluation. However, it does not explicitly define "acceptance criteria" in a table format with specific numerical targets. Instead, it details the results of various performance tests as evidence that the device meets acceptable standards, primarily by demonstrating substantial equivalence to a predicate device.

Here's an interpretation of the acceptance criteria and study that can be extracted from the provided information:

Interpretation of Acceptance Criteria and Study Design:

The VITEK® COMPACT PRO is an automated antimicrobial susceptibility testing system. The core of its acceptance criteria and the study proving it meets these criteria relies on demonstrating substantial equivalence to a previously cleared VITEK® 2 System (N50510 Supplement S082). This means the new device must perform comparably to the predicate device across various metrics.

1. Table of Acceptance Criteria (Inferred) and Reported Device Performance:

Since explicit acceptance criteria are not tabulated with thresholds, they are inferred from the reported performance, with the implicit criterion being "comparable to or better than the predicate device."

2. Sample Sizes Used for the Test Set and Data Provenance:

• QC Testing: Each of the 13 quality control organisms was tested at least twenty times. This testing was conducted at "at least three of the clinical evaluation trial sites."
• Reproducibility: Isolates were tested in triplicate for three trial sites. Individual test sets were selected for each antimicrobial, with each set including a minimum of 10 strains (at least 2 with on-scale results).
• Clinical Performance Evaluation: "Representative, clinically relevant strains" were tested. Each strain was tested one time with both the VITEK® COMPACT PRO and the VITEK® 2.
• Data Provenance: The document states testing was done at "at least three of the clinical evaluation trial sites" for QC and "three trial sites" for reproducibility. The country of origin for these sites is not specified, but bioMérieux Inc. is located in Hazelwood, Missouri, USA, implying the studies were likely conducted in the US. The studies appear to be prospective as they involve new testing of isolates for performance evaluation.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts:

This information is not explicitly stated in the provided text. The ground truth for the clinical performance evaluation was established by comparing the VITEK® COMPACT PRO's results against the VITEK® 2 System's results (N50510 Supplement S082), which implicitly serves as the "expert consensus" or "reference method" in this context. The document does not describe a separate human expert panel for adjudication or ground truth establishment the way it might for an AI imaging device.

4. Adjudication Method for the Test Set:

Not applicable in the traditional sense of human expert adjudication. The comparison was directly between the new device (VITEK® COMPACT PRO) and the predicate device (VITEK® 2 System) for MICs and interpretations (S/SDD/I/R). There's no mention of a 2+1 or 3+1 human expert adjudication process.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

No, an MRMC study was not done. This device is an automated in vitro diagnostic instrument, not an AI-assisted imaging device for human interpretation. The comparison is machine-to-machine (new instrument vs. predicate instrument).

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

Yes, the primary performance evaluation was a standalone "algorithm only" (instrument only) performance comparison. The VITEK® COMPACT PRO (device under test) generated MICs and interpretations, and these were directly compared to those generated by the predicate VITEK® 2 System. Human "in-the-loop" performance is not relevant for the core function of this automated susceptibility system in the context of its performance study.

7. The type of ground truth used:

The ground truth for the clinical performance evaluation was the MIC results and categorical interpretations (S/SDD/I/R) obtained from the legally marketed predicate device, the VITEK® 2 System (N50510 Supplement S082). This serves as the reference method against which the new device's performance is measured.

8. The Sample Size for the Training Set:

The document does not discuss a separate "training set" in the context of device development or performance evaluation. This is not an AI/ML device where a distinct training dataset is typically used. The development process likely involved internal verification and validation, but the reported studies (QC, Reproducibility, Clinical Performance) are essentially testing/validation datasets.

9. How the ground truth for the training set was established:

Not applicable, as no explicit training set for an AI/ML algorithm is described.

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The BD Phoenix Automated Microbiology System is intended for the in vitro rapid identification (ID) and the quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most Gram-positive bacteria from pure culture belonging to the genera Staphylococcus, other gram positive cocci and gram positive bacilli and of most Gram-negative aerobic and facultative anaerobic bacteria isolates from pure culture for Enterobacteriaceae and Non-Enterobacteriaceae.

BD Phoenix is an automated system for the rapid identification (ID) and antimicrobial susceptibility testing (AST) of clinically relevant bacterial isolates. The BD Phoenix System utilizes a redox indicator to detect organism growth in the presence of an antimicrobial agent. Measurements of changes to the indicator as well as bacterial turbidity are used in the determination of bacterial growth. Each AST panel configuration contains several antimicrobial agents with a wide range of two-fold doubling dilution concentrations. The Phoenix instrument reads and records of the antimicrobial tests contained in the panel and interprets the reactions (based on the organism identification) to give a minimal inhibitory concentration (MIC) value and category interpretations (susceptible, intermediate, resistant, or not susceptible).

The BDXpert™ System is a rule-based software tool that provides expert advice based on organism ID and AST results obtained by broth micro-dilution on the BD Phoenix Instruments. BDXpert rule development is based on published information available through standards organizations, current scientific literature, and FDA's STIC; custom rules may be user defined if desired. The BDXpert System rule logic is applied to the susceptible, intermediate, and resistant (SIR) result, which is based on the breakpoint table and interpretation rule set included either in the BDXpert System on the standalone Phoenix instruments or through the BDXpert System on the connected BD EpiCenter™ data management system (EpiCenter) or BD Synapsys™ Informatics Solution (Synapsys). The resulting instrument report contains information such as: MIC interpretation, BDXpert rules, special messaging, resistance markers, etc. The expert results can then be sent to the Laboratory Information System (LIS).

Synapsys is a browser-based software platform operating in the clinical lab setting, offering secure connectivity and data storage, integrated workflows, and analytics tools. Synapsys consists of software servers operating the application and database, securely networked through a facility IT infrastructure to diagnostic instrumentation, external healthcare IT systems such as the LIS, and browser-enabled client devices for operating the system. Synapsys connects BD lab automation and diagnostic instruments to a common database and provides a single user interface to integrate laboratory workflows. Synapsys provides bi-directional communication with BD Phoenix and is able to process ID and AST results received from a BD Phoenix instrument. The system will automatically associate a known organism ID result, regardless of source, to any ID/AST or AST only Phoenix panel(s) that have the same accession/isolate number and lack an organism ID.

While the provided text describes an FDA 510(k) premarket notification for the BD Phoenix™ Automated Microbiology System, it does not contain the detailed information necessary to answer your specific questions regarding acceptance criteria and the study that proves the device meets them.

The document primarily focuses on:

• Regulatory clearance: The FDA's determination of substantial equivalence to a predicate device.
• Device description: How the BD Phoenix system works for identification (ID) and antimicrobial susceptibility testing (AST).
• Comparison to predicate: Highlighting similarities and differences, particularly in data management connectivity (Synapsys vs. EpiCenter).
• General compliance: Mentioning adherence to standards like ISO 13485, IEC 62304, and ISO 14971, and FDA guidance on software functions.

Missing Information:

The document explicitly states under "V. Performance Characteristics (if/when applicable)": "Performance testing was conducted to verify compliance with specified design requirements... Software verification and validation activities demonstrate that BD Phoenix Instrument connected to Synapsys will perform as intended when used in accordance with device labeling." However, it does not provide the results of these performance tests, nor does it detail the specific acceptance criteria or the methodology of the study that generated those results.

Therefore, I cannot populate the table or answer the specific questions about the study design, sample sizes, ground truth establishment, or expert involvement based solely on the provided text. This type of detailed performance data is typically found in the full 510(k) submission, which is more extensive than this summary letter.

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The BD Phoenix™ Automated Microbiology System is intended for in vitro quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most Gram-negative and facultative anaerobic bacteria isolates from pure culture for Enterobacteriaceae and most Gram-positive bacteria isolates from pure culture belonging to the genera Staphylococcus, and Streptococcus, This premarket notification is for the BD Phoenix™ Automated Microbiology System with Ciprofloxacin at a concentration of 0.0156-4 ug/mL. Ciprofloxacin has been shown to be active in vitro against most strains of microorganisms listed below, as described in the FDA-approved package insert for this antimicrobial agent.

This submission is for a range extension of a single antimicrobial cleared for use on BD Phoenix ID/AST or AST only panels. The ID portion of the ID/AST combination panel was not subject to review in this submission.

The Phoenix AST method is a broth-based microdilution test. The Phoenix panel is a sealed and self-inoculating molded polystyrene tray with 136 micro-wells containing dried reagents. The ID/AST combination panel includes an ID side (51 wells) with dried substrates for bacterial identification and an AST side (85 wells). The AST panel contains a wide range of two-fold doubling dilution concentrations of antimicrobial agents and growth and fluorescent controls at appropriate well locations. The AST panel does not include wells for isolate identification.

The Phoenix System utilizes a redox indicator for the detection of organism growth in the presence of an antimicrobial agent. The organism to be tested must be a pure culture and be preliminarily identified as Gram-positive or Gram-negative. Colonies are then suspended in ID broth and equated to a 0.5 McFarland suspension using a nephelometer device. A further dilution is made into AST broth (a cation-adjusted formulation of Mueller-Hinton broth containing 0.010% Tween 80), to which the redox-buffered oxidation-reduction AST indicator solution is added producing a blue color in the wells. The concentration of organisms in the final AST broth suspension is approximately 5 X 105 CFU/mL.

The Phoenix AST Broth is poured into the inoculation port of the AST panel and the inoculum flows into the panel, filling panel wells. Polyethylene caps are applied to seal the inoculation ports. An air admittance port is located in the panel lid to ensure adequate oxygen tension in the panel for the duration of the test. Inoculated panels are barcode scanned and loaded into the BD Phoenix Automated Microbiology System instrument where panels are continuously incubated at 35 ℃ ± 1 ℃.

Continuous measurements of changes to the indicator as well as bacterial turbidity are used in the determination of bacterial growth. The instrument takes readings every 20 minutes. Organisms growing in the presence of a given antimicrobial agent reduce the indicator (changing it to a pink color). This signals organism growth and resistance to that antimicrobial agent. Organisms killed or inhibited by the antimicrobial agent do not cause reduction of the indicator and therefore do not produce a color change. The Phoenix instrument reads and records the results of the antimicrobial tests contained in the panel and interprets the reactions (based on the organism identification) to give a minimal inhibitory concentration (MIC) value and category interpretations (susceptible, intermediate, resistant, or not susceptible). AST results are available within 16 hours. This is an auto read result; no manual readings are possible with this system.

Additional comments concerning specific organism/antimicrobial combinations are provided from the software-driven expert system (BDXpert), using rules derived from CLSI documentation and/or the FDA-approved drug labeling.

The BD Phoenix Automated Microbiology System - GN Ciprofloxacin (0.0156-4 ug/mL) is an antimicrobial susceptibility testing system. The provided text describes the performance characteristics of this device, particularly for Salmonella species, and the study conducted to demonstrate its performance against acceptance criteria.

1. Table of Acceptance Criteria and Reported Device Performance:

(Note: The document states "The BD Phoenix Ciprofloxacin performance met the acceptance criteria for Salmonella with overall EA and CA greater than 90%." The specific numerical acceptance criteria for Min, Maj, Vmj are usually found in the referenced guidance documents but are not explicitly detailed as numerical percentages in the provided text for the device itself, other than the observed performance.)

2. Sample Size Used for the Test Set and Data Provenance:

• Clinical Isolates: 47 (fresh: 7 (14.9%), stock: 40 (85.1%))
  • Organisms: Salmonella species (43 isolates), Salmonella enterica ssp. enterica serovar Typhi (4).
  • Provenance: "Clinical testing was conducted at three U.S. sites." (Suggests prospective and retrospective clinical data from U.S. sources).
• Challenge Isolates: 82 stock isolates
  • Organisms: Salmonella species (79), Salmonella enterica ssp. enterica serovar Typhi (3).
  • Provenance: "Additional stock challenge isolates were tested at each study site." (Implying laboratory-controlled challenge strains, likely geographically diverse or from culture collections, but no specific country of origin is mentioned beyond "U.S. sites" for the clinical part which also conducted challenge testing).
• Reproducibility Study Isolates: 14 isolates of non-fastidious Gram-negative organisms (including Pseudomonas aeruginosa (1), Salmonella enterica ssp. enterica serovar Paratyphi A (1), and Salmonella species (11)).

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications:

The ground truth was established using the CLSI frozen broth microdilution reference panel, prepared according to CLSI M07 guidelines. This is a standardized laboratory reference method, implicitly implying experts in microbiology and antimicrobial susceptibility testing were involved in its execution and interpretation, rather than individual "experts" reviewing each case for a ground truth panel. The document does not specify the number or qualifications of "experts" as individuals but relies on the standardized, recognized reference method.

4. Adjudication Method for the Test Set:

Not applicable in the typical sense of expert adjudication for diagnostic imaging or similar devices. The ground truth is determined by a universally accepted reference laboratory method (CLSI frozen broth microdilution). The comparison involves measuring agreement between the device and this reference method.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:

A multi-reader multi-case (MRMC) comparative effectiveness study was not conducted. The study focuses on the standalone performance of the automated system against a reference method, not on human reader performance with or without AI assistance.

6. Standalone (Algorithm Only) Performance:

Yes, a standalone performance study was conducted. The "BD Phoenix Automated Microbiology System" is an automated device, and its performance was evaluated against a reference method (CLSI frozen broth microdilution) without human intervention in the MIC determination or category interpretation on the device side. The reported Essential Agreement (EA) and Category Agreement (CA) metrics represent this standalone algorithmic performance.

7. Type of Ground Truth Used:

The ground truth used was expert consensus methodology/reference standard, specifically the CLSI frozen broth microdilution reference panel prepared according to CLSI M07 guidelines. This is the gold standard for antimicrobial susceptibility testing.

8. Sample Size for the Training Set:

The document does not explicitly state the sample size for a training set. This type of device (AST system) is typically developed and validated against extensive datasets during its initial creation and subsequent range extensions. However, the provided text describes the validation/test set used for this specific premarket notification (47 clinical isolates and 82 challenge isolates for Salmonella). This suggests a re-evaluation of performance based on updated breakpoints rather than a new algorithm development requiring a separate training set description in this 510(k) summary.

9. How the Ground Truth for the Training Set Was Established:

As no explicit training set sample size is provided, the method for establishing its ground truth is also not detailed. However, if a training phase was involved in the initial development of the BD Phoenix system, it would have traditionally relied on similar reference methodologies like CLSI broth microdilution to establish accurate MIC values and corresponding susceptibility categories.

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VITEK® 2 AST-Gram Positive Lefamulin is designed for antimicrobial susceptibility testing of Gram positive microorganisms and is intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents.

VITEK® 2 AST-Gram Positive Lefamulin is a quantitative test. Lefamulin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active both in vitro and in clinical infections: Staphylococcus aureus (methicillin-susceptible isolates)

The VITEK® 2 Gram-positive Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of Staphylococcus spp., and S. agalactive to antimicrobial agents when used as instructed.

The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh (1) and Gerlach (2). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique (0).

Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

VITEK® 2 AST-GP Lefamulin (≤ 0.03 –>4 µg/mL) has the following concentrations in the card: 0.125, 0.5, 1, and 2 (equivalent standard method concentration by efficacy in ug/mL).

The VITEK® 2 AST-Gram Positive Lefamulin (≤ 0.03 - ≥4 µg/mL) device is an antimicrobial susceptibility testing system designed for Gram-positive microorganisms. The acceptance criteria and performance of the device are detailed below.

1. Table of Acceptance Criteria and Reported Device Performance

2. Sample size used for the test set and the data provenance

The test set included:

• 404 isolates for Essential Agreement reporting and 404 isolates for Category Agreement reporting (derived from the numerators/denominators in Table 2).
• 3 resistant isolates were tested for VME (Very Major Error)
• 401 susceptible isolates were tested for ME (Major Error)

The data provenance is described as an "external evaluation" conducted with "fresh and stock clinical isolates, as well as a set of challenge strains." The document does not specify the country of origin of the data or explicitly state whether the study was retrospective or prospective.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

This information is not provided in the given text.

4. Adjudication method for the test set

This information is not provided in the given text.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

A multi-reader multi-case (MRMC) comparative effectiveness study with human readers assisted by AI is not applicable to this device. This device is an automated antimicrobial susceptibility test system, not an AI-assisted diagnostic tool interpreted by human readers.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

Yes, a standalone performance evaluation was done. The VITEK® 2 AST-GP Lefamulin system's performance was compared directly to the CLSI broth microdilution reference method (the ground truth), without human intervention in the interpretation of the VITEK® 2 results. The system automatically generates MIC values and interpretive categories.

7. The type of ground truth used

The ground truth used was the CLSI broth microdilution reference method, incubated at 16-20 hours.

8. The sample size for the training set

The document does not explicitly mention a separate "training set" or its sample size. The description focuses on the external evaluation data used for performance assessment. As an AST system, the device's "training" for MIC determination is inherent in its design based on established microdilution principles and may not involve a distinct, large-scale machine learning training set in the way an AI algorithm might.

9. How the ground truth for the training set was established

Since a distinct training set is not explicitly mentioned as per the prompt's context (e.g., for an AI algorithm), details on how its ground truth was established are not provided. The device's operation is based on established microbiological principles, and its performance is validated against the CLSI broth microdilution reference method.

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The Colibrí is an automated in vitro diagnostic specimen preparation system for use with WASPLab to prepare MALDI-TOF targets for the bioMérieux VITEK MS systems or Bruker MALDI Biotyper CA mass spectrometry systems for qualitative identification and microbial suspension for the bioMérieux VITEK 2 systems or Beckman Coulter MicroScan WalkAway Antimicrobial Susceptibility Testing (AST) systems for qualitative testing of isolated colonies of gram-negative and gram-positive bacterial species grown on solid culture media.

The Colibrí is an automated pre-analytical processor that picks isolated colonies designated by the operator and uses a pipetting system to prepare MALDI-TOF MS (Matrix-Assisted Laser Desorption/lonization-Time of Flight Mass Spectrometry) target slides for bacterial identification and microbial suspension at known concentration for Antimicrobial Susceptibility Testing and purity assessment.

The Colibrí software records the identity of each sample and its position on the target slide and communicates this information electronically to the MALDI-TOF MS analyzers.

Bacterial suspensions for AST and purity plates are identified by barcode label.

The Colibrí is intended for use by trained healthcare professionals in clinical laboratories in conjunction with other clinical and laboratory findings, including Gram staining, to aid in the diagnosis of bacterial infections.

The Colibrí has not been validated for use in the identification or processing of yeast species, molds, Nocardia, or mycobacteria.

The Colibrí is an instrument which automates the picking of selected colonies from plated media and prepares MALDI target slides for the bioMérieux VITEK MS systems or the Bruker MALDI Biotyper CA systems that are used in clinical laboratories for identification and differentiation of organisms grown on plated media by Matrix-Assisted Laser Desorption/Jonization Time-of Flight Mass Spectrometry (MALDI-TOF MS). The Colibri automates the preparation of microbial suspensions at known concentration for bioMérieux VITEK 2 systems and Beckman Coulter MicroScan WalkAway systems that are used in clinical laboratories for AST analyses. Moreover, the Colibrí is used for Purity Plates preparation for purity assessments.

The Colibrí includes the following components:

• Colibrí instrument and software with on-board pipetting system and nephelometer .
• Colibrí Primary Tubes
• Colibrí Spreader
• Colibrí Daily Verification kit.

Colibri is designed to be used in conjunction with the WASPLab device for culture plate incubation and image analysis. After appropriate plate incubation, the operator selects the colonies from a digital image of culture media plate streaked with microbiological human specimen, available through WebApp software, the WASPLab User Interface.

The operator assigns the automatic ID or AST tasks to the isolated colonies to be processed. Then, the operator loads the plates in the Collbri where colonies are automatically picked, spotted on the target slide and overlayed with the matrix or suspended into the dedicated solution for the preparation of the microbial suspension for AST purposes (Secondary Tube).

When used in conjunction with the bioMérieux VITEK MS systems, the Colibri can prepare the 48-spot target slides by performing the direct spotting of colonies. The calibrator used for quality control is manually applied by the operator at the end of the automated colony spotting. When used in conjunction with the Bruker MALDI Biotyper CA systems, the Colibri can prepare either reusable 48-spot or disposable 96-spot targets by performing the Direct Transfer Sample Procedure. The BTS used for quality control is manually applied by the operator at the end of the automated colony spotting.

When used in conjunction with the bioMérieux VITEK 2 systems or the Beckman Coulter MicroScan WalkAway systems, the Colibri can prepare the microbial suspension at the proper concentration by direct colony suspension method. The onboard nephelometer allows the preparation of Secondary Tubes (AST suspensions) at the correct concentration and the Colibri Spreader is used for Purity Plates preparation.

The Colibrí software records the identity of each sample and its position on the target slide and communicates this information electronically to the MALDI-TOF MS analyzers.

The traceability of prepared Secondary Tube and Purity Plates is maintained by dedicated labels applications.

Colibrí requires four different calibrations, one on the nephelometer, three on the cameras. None of these calibration activities require user intervention if not in terms of periodical cleaning of the mechanical component as described in the dedicated section of the User Manual. The Set-up calibration of nephelometer and camera units are performed during the device initial setup. Auto-calibration is performed at the end of the initial set-up and periodically during the preventive maintenance to check that all the mechanical references can be found inside the positioning tolerances, that the I/Os are responsive. Runtime calibration is performed during the normal usage to automatically check the proper functioning of the Colibrí.

Colibrí requires a daily nephelometer verification to check the proper reading of suspensions at different turbidity values.

The Colibrí device is an automated in vitro diagnostic specimen preparation system. The provided text describes the acceptance criteria and the study that proves the device meets these criteria for preparing microbial suspensions for Antimicrobial Susceptibility Testing (AST) using Beckman Coulter MicroScan WalkAway systems.

Here's a breakdown of the requested information:

1. A table of acceptance criteria and the reported device performance:

The acceptance criteria are implicitly derived from the successful outcomes of the analytical studies. The performance is reported as the percentage of successful outcomes for each metric.

• E. coli ATCC 25922: 3-7 x 105 CFU/mL
• Other bacteria: 2-8 x 105 CFU/mL | 98.5% of prepared suspensions had microbial concentration within acceptable limits.
• E. coli: 100% (36/36)
• Pseudomonas aeruginosa: 96.7% (29/30)
• Staphylococcus aureus: 97.6% (41/42)
• Enterococcus faecalis: 100% (30/30) |
  | AST Challenge Test (Agreement with Manual Preparation) | Essential Agreement (EA) of MICs: High agreement
  Category Agreement (CA): High agreement
  Discrepancies (vmj, maj): Low/none | Overall EA: 100% (1232/1232 evaluable MIC results within 1 two-fold dilution)
  Overall CA: 98.4% (4187/4254 SIR categorizations in agreement)
  Very Major discrepancy (vmj): 0
  Major discrepancy (maj): 0 |
  | Reproducibility Study | Best-case reproducibility: ≥95% (implied)
  Worst-case reproducibility: ≥89% (implied) | Best-case reproducibility: ≥99.8% (all panels combined)
  Worst-case reproducibility: ≥94.3% (all panels combined) |
  | Sample preparation for Quality Control | 100% of MIC values within CLSI/panel IFU QC range | 100% (all tested organisms and antimicrobial agents) |
  | Purity Plates Evaluation (Cross-contamination) | Absence of cross-contamination (100% monomicrobial growth) | 100% (453/453 Purity Plates showed monomicrobial growth) |

2. Sample sizes used for the test set and the data provenance:

• Preparation of Microbial Suspensions for AST:

  • Test Set Size: 132 microbial suspensions (36 E. coli, 30 Pseudomonas aeruginosa, 42 Staphylococcus aureus, 30 Enterococcus faecalis).
  • Data Provenance: Not explicitly stated (e.g., country of origin). The study involved three Colibrí instruments, suggesting internal validation. Retrospective or prospective is not specified, but the nature of the validation suggests prospective testing.

• AST Challenge Test:

  • Test Set Size: Different species: Enterobacterales (n=50 isolates), Staphylococcus (n=20 isolates), Streptococcus (n=12 isolates), Enterococcus (n=18 isolates), non-fermenters (n=10 isolates). Each processed by three Colibrí instruments, yielding varying numbers of MIC results and SIR categorizations across different panels (e.g., 2454 total MIC results for Enterobacterales on NM-NF50 panel).
  • Data Provenance: Not explicitly stated (e.g., country of origin). The study design implies prospective testing within the manufacturer's validation process.

• Reproducibility Study:

  • Test Set Size: 9 gram-positive and 9 gram-negative strains, processed on 3 Colibrí instruments over 3 days, with each condition tested in triplicate (total of 27 replicates for each strain-antimicrobial agent combination).
  • Data Provenance: Not explicitly stated (e.g., country of origin, retrospective or prospective). Implied prospective.

• Sample preparation for Quality Control:

  • Test Set Size: CLSI-recommended reference strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212). The "No. MIC within QC range" indicates a total of 30 or 36 or 42 tests for each drug-organism combination, per three instruments.
  • Data Provenance: Not explicitly stated. Implied prospective.

• Purity Plates Evaluation:

  • Test Set Size: 453 purity plates (150 from AST Challenge, 162 from AST Reproducibility, 141 from Quality Control studies).
  • Data Provenance: Not explicitly stated. Implied prospective.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

• The ground truth for AST results (MICs and SIR categories) generally refers to the results obtained from a reference method. In this case, "Manual suspension was used as comparative method" for the AST Challenge Test. This implies that manually prepared suspensions, processed by the MicroScan WalkAway, served as the reference standard.
• The text does not specify the number of experts or their qualifications for establishing this manual ground truth. It mentions that three different technicians operated the Colibrí machines, but it doesn't detail the personnel for the manual comparative method or for interpreting the results as ground truth beyond the "FDA-Recognized Antimicrobial Susceptibility Test Interpretive Criteria" and CLSI guidelines.

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

• The document does not describe any expert adjudication process for the test set results. The comparison is made against a "manual result" (ground truth). The discrepancies (vmj, maj, min) are simply categorized and reported, implying a direct comparison without further expert review for resolving initial disagreements.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

• No, an MRMC study was not conducted. This device (Colibrí) is an automated system for sample preparation and does not involve human "readers" or "AI assistance" in the typical sense of image analysis for diagnosis. Its role is to automate a laboratory process, and the performance is measured against reference methods, not human interpretation.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

• The studies presented are primarily standalone (algorithm only without human-in-the-loop performance) in terms of the Colibrí device's automated functions. The device picks colonies, prepares suspensions, and records data automatically. The performance metrics (inoculum density, MIC accuracy, reproducibility, purity) assess the device's output against established standards and manual methods.
• While an operator designates colonies for picking, the act of preparation itself is automated and evaluated for its accuracy. The "manual suspension" used for comparison acts as the reference for the "algorithm only" performance of the Colibrí in producing the suspension.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc):

• The ground truth for the analytical studies combines reference methods/standards and established guidelines:
  • For microbial suspension concentration: Viable cell count (CFU/mL) against CLSI and FDA guidelines.
  • For AST results: Manual suspension preparation as the comparative method, and comparison of MICs and SIR categories against FDA-Recognized Antimicrobial Susceptibility Test Interpretive Criteria and CLSI guideline M07.
  • For reproducibility: Comparison to the "mode result" (most frequent MIC value) and established reproducibility criteria (e.g., within one doubling dilution).
  • For Quality Control: CLSI-recommended QC ranges and MicroScan panel IFU values.
  • For Purity Plates: Visual assessment (implied) to confirm monomicrobial growth.

8. The sample size for the training set:

• This document describes performance validation studies for a medical device (Colibrí), not a machine learning model. Therefore, there is no "training set" in the context of data used to train an AI algorithm. The Colibrí is an automated instrument with pre-programmed functions, not a learning algorithm that requires a training dataset.

9. How the ground truth for the training set was established:

• As explained above, there is no training set for this device in the context of AI/ML.

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VITEK® 2 Streptococcus Penicillin is designed for antimicrobial susceptibility testing of Streptococcus species and is intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. VITEK® 2 Streptococcus Penicillin is a quantitative test. Penicillin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active both in vitro and in clinical infections: Beta hemolytic Streptococci groups C and G Streptococcus pyogenes Streptococcus agalactiae Streptococcus viridans group Streptococcus pneumoniae

The VITEK® 2 Streptococcus Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of Sireptococcus pneumoniae, beta-hemolytic Streptococcus, and Viridans Streptococcus to antimicrobial agents when used as instructed.

The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh(1) and Gerlach(2). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique(3).

Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

VITEK® 2 Streptococcus Penicillin has the following concentrations in the card: 0.06, 0.12, 0.5, and 2ug/mL (equivalent standard method concentration by efficacy in ug/mL).

Here's a summary of the acceptance criteria and study details for the VITEK® 2 Streptococcus Penicillin device:

1. Acceptance Criteria and Reported Device Performance

The device performance is compared to the broth microdilution reference method. The key metrics are Essential Agreement (EA) and Category Agreement (CA), along with Very Major Errors (VME), Major Errors (ME), and Minor Errors (mE).

The document states that the device "demonstrated substantially equivalent performance when compared with the broth microdilution reference method, as defined in the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA (Issued August 28, 2009)." This guidance document typically outlines specific numerical acceptance criteria for EA, CA, VME, ME, and mE, which are implicitly met by the reported percentages being considered "acceptable."

2. Sample Size Used for the Test Set and Data Provenance

The sample sizes for the test set are embedded within the "Reported Device Performance" column (e.g., 350 for Streptococcus pneumoniae (non-meningitis), 391 for Streptococcus Viridans group, 833 for Beta-hemolytic Streptococcus).

The data provenance is from "external evaluation... conducted with fresh and stock clinical isolates, as well as a set of challenge strains." This implies a combination of retrospective (stock clinical isolates) and prospective (fresh clinical isolates) data. The country of origin of the data is not specified in the provided text.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

This information is not provided in the document. The ground truth is established by the CLSI broth microdilution reference method, but details on expert involvement in this process (e.g., reading/interpreting the reference method results) are not mentioned.

4. Adjudication Method for the Test Set

This information is not explicitly provided in the document. The study compares the VITEK® 2 results to the CLSI broth microdilution reference method. Adjudication might be part of the standard CLSI method, but it is not detailed here for discrepancies.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This study focuses on the performance of an automated diagnostic device against a reference method, not on human reader performance with or without AI assistance.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, a standalone performance study was done. The VITEK® 2 system is a "Fully Automated Short-Term Incubation Cycle Antimicrobial Susceptibility System," and its performance was evaluated against the CLSI broth microdilution reference method. This is an evaluation of the algorithm's output (MIC values and interpretive categories) without direct human intervention in the interpretation of the VITEK® 2 results.

7. The Type of Ground Truth Used

The type of ground truth used is the broth microdilution reference method, specifically the CLSI method incubated at 16-20 hours. This is typically considered the gold standard for antimicrobial susceptibility testing.

8. The Sample Size for the Training Set

The document does not explicitly state the sample size for the training set. The study describes "external evaluation" for performance, but it doesn't separate out a specific training set size for the VITEK® 2 algorithm itself.

9. How the Ground Truth for the Training Set Was Established

The document does not explicitly state how the ground truth for any training set was established, as it primarily focuses on the performance evaluation of the final device against a reference method. However, given that the device is an "Automated quantitative antimicrobial susceptibility test," it's highly probable that any internal training/development would have used an established reference method (like broth microdilution) to establish ground truth for algorithm development.

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VITEK® 2 AST-Gram Positive Daptomycin is designed for antimicrobial susceptibility testing of Gram positive microorganisms and is intended for use with the VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. VITEK® 2 AST-Gram Positive Daptomycin is a quantitative test. Daptomycin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active both in vitro and in clinical infections: Enterococcus faecalis (vancomycin-susceptible isolates only) Staphylococcus aureus (including methicillin-resistant isolates)

In vitro data are available, but their clinical significance is unknown: Enterococcus faecalis (vancomycin-resistant isolates)

The VITEK® 2 Gram-positive Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of Staphylococcus spp., Enterococcus spp., and S. agalactiae to antimicrobial agents when used as instructed.

The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh(1) and Gerlach(2). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique(3).

Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

VITEK® 2 AST-GP Daptomycin has the following concentrations in the card: 0.5, 1, 2, 4, and 8 ug/mL (equivalent standard method concentration by efficacy in ug/mL).

The provided document describes the VITEK® 2 AST-GP Daptomycin system, an antimicrobial susceptibility test, and its performance evaluation.

Here's an analysis of the acceptance criteria and the study proving the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for antimicrobial susceptibility test (AST) systems in the US are generally defined by the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems. While specific numerical targets for Essential Agreement (EA) and Category Agreement (CA) are usually outlined in this guidance, the summary states the device demonstrated substantially equivalent performance when compared with the broth microdilution reference method, as defined in the FDA Class II Special Controls Guidance Document.

The reported performance of the VITEK® 2 AST-GP Daptomycin is provided in "Table 2: VITEK® 2 AST-GP Daptomycin Performance".

Note on VME/ME/mE for Staphylococcus aureus: The document lists "N/A" for VME and mE for Staphylococcus aureus and "0.0%" for ME for Enterococcus faecalis. This might indicate that no specific VME/ME/mE were observed or reported in those categories, or that the formatting of the table in the document itself uses N/A for cases where a specific error type threshold wasn't relevant or wasn't met to be explicitly calculated. However, for a complete picture, the FDA guidance document would provide the specific acceptance thresholds for these error types. The (1/8) 12.5% VME for Enterococcus faecalis and (41/270) 15.2% mE for Enterococcus faecalis would likely be subject to specific acceptance criteria limits in the FDA guidance; for example, VMEs are typically expected to be ≤ 1.5% and MEs ≤ 3.0%, while mEs generally have a higher tolerance but still a limit. The document states a 90.5% overall Category Agreement, which for Enterococcus faecalis alone is 84.4%, falling below the typical 90% threshold for CA. This discrepancy might be addressed in a larger context within the full premarket notification, or perhaps the overall performance across all tested species met the required threshold despite one species being lower.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size:
  • Staphylococcus aureus: 194 isolates
  • Enterococcus faecalis: 270 isolates
  • Total Clinical Isolates in Performance Study: 194 + 270 = 464 isolates.
  • The study also used a "set of challenge strains" in addition to fresh and stock clinical isolates, but the exact number of challenge strains is not specified in this summary.
• Data Provenance:
  • "An external evaluation was conducted with fresh and stock clinical isolates, as well as a set of challenge strains." This suggests a prospective or a mix of prospective and retrospective collection from external sources (likely clinical laboratories).
  • The document does not specify the country of origin for the data.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of those Experts

• The ground truth was established by the CLSI broth microdilution reference method. This method is a standardized laboratory procedure, not reliant on human expert interpretation in the same way as, for example, image reading. Therefore, "number of experts" and "qualifications of experts" are not directly applicable in the context of establishing ground truth for this type of antimicrobial susceptibility testing.

4. Adjudication Method for the Test Set

• The reference method itself (CLSI broth microdilution) serves as the "ground truth" or "adjudication." No separate human adjudication process (e.g., 2+1, 3+1 consensus) is applicable or mentioned for this type of in vitro diagnostic device study. The device's results are directly compared to the results of the reference method.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

• No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This type of study design is typically used for AI-powered diagnostic imaging devices where human readers interpret images with or without AI assistance. This device is an automated in vitro diagnostic system for antimicrobial susceptibility testing, not requiring human interpretation of complex visual data for its primary function.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

• Yes, the performance study effectively evaluates the "standalone" performance of the VITEK® 2 AST-GP Daptomycin system. The system automatically processes the samples and generates MIC values and interpretive categories, which are then compared directly to the CLSI broth microdilution reference method. There is no human intervention in the device's determination of susceptibility.

7. The Type of Ground Truth Used

• The ground truth used was the CLSI broth microdilution reference method, which is a highly standardized and accepted laboratory method for determining antimicrobial susceptibility. This is essentially a "gold standard" laboratory method.

8. The Sample Size for the Training Set

• The document does not provide information on the training set size. This type of premarket notification summary focuses on the performance evaluation of the final device, not typically on the specific dataset used for algorithm development or training. The "Discriminant Analysis" mentioned under "Analysis Algorithms" implies a statistical model was used, which would have been developed/trained on a dataset, but details of this dataset are not included in this summary.

9. How the Ground Truth for the Training Set Was Established

• As the training set details are not provided, the method for establishing its ground truth is also not described in this summary. It would logically be established using a similar or identical reference method to the test set, but this is not confirmed.

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