(79 days)
The BD Phoenix™ Automated Microbiology System is intended for the rapid identification and in vitro antimicrobial susceptibility testing of isolates from pure culture of most aerobic and facultative anaerobic Gram-negative and Gram-positive bacteria of human origin.
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 Enterobacteriaceae and Non-Enterobacteriaceae and most Gram-positive bacteria isolates from pure culture belonging to the genera Staphylococcus, Enterococcus and Streptococcus.
This premarket notification is for the addition of the Phoenix Inducible Macrolide Resistance (iMLSb) Test in Staphylococcus species to Gram-positive ID/AST or AST only Phoenix panels. The Phoenix Inducible Macrolide Resistance Test is used to detect inducible macrolide-lincosamide-streptogramin B resistance in Staphylococcus species.
The BD Phoenix Automated Microbiology System (Phoenix System) is an automated system for the rapid identification (ID) and antimicrobial susceptibility testing (AST) of clinically relevant bacterial isolates. The system includes the following components:
- . BD Phoenix instrument and software.
- . BD Phoenix panels containing biochemicals for organism ID testing and antimicrobial agents or AST determinations.
- BD Phoenix ID Broth used for performing ID tests and preparing AST Broth inoculum. .
- BD Phoenix AST Broth used for performing AST tests only. .
- BD Phoenix AST Indicator solution added to the AST Broth to aid in bacterial growth . determination.
The Phoenix panel is a sealed and self-inoculating molded polystyrenc tray with 136 micro-wells containing dried reagents. Organisms for susceptibility testing must be a pure culture and preliminarily identified as a Gram-negative or Gram-positive isolate. Phoenix panels are inoculated with a specified organism density and placed into the instrument.
The Phoenix AST method is a broth based microdilution test. The Phoenix System utilizes a redox indicator for the detection of organism growth in the presence of an antimicrobial agent. Measurcments 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 instrument houses the panels where they are continuously incubated at a nominal temperature of 35°C. The instrument takes readings of the panels every 20 minutes. The readings are interpreted to give an identification of the isolate, minimum inhibitory concentration (MIC) values and category interpretations, S, I, R or N (susceptible, intermediate, resistant or not susceptible).
The provided text describes the BD Phoenix™ Automated Microbiology System for detecting inducible macrolide resistance (iMLSb) in Staphylococcus species. Here's a breakdown of the acceptance criteria and the study that proves the device meets them:
1. A table of acceptance criteria and the reported device performance
| Acceptance Criteria Category | Acceptance Criteria (Implicit) | Reported Device Performance |
|---|---|---|
| Site Reproducibility | Overall intra-site reproducibility > 90% | Overall intra-site reproducibility of greater than 90% for the Gram-positive isolates tested. |
| Overall inter-site reproducibility > 95% | Overall inter-site reproducibility of greater than 95% for the Gram-positive isolates tested. | |
| Clinical Performance | Substantial equivalence to the CLSI reference broth microdilution method and the CLSI Disk Approximation Test for iMLSb detection. Specific performance metrics (e.g., Categorical Agreement, Essential Agreement) would be expected based on FDA guidance, but only Categorical Agreement (CA) is explicitly stated for the iMLSb test. | For the Phoenix Inducible Macrolide Resistance Test in Staphylococcus species, the Clinical Agreement (CA) was 97.6% (n=295). The study concludes "substantially equivalent performance when compared with the CLSI (formerly NCCLS) reference broth microdilution method" and "substantially equivalent to the CLSI Disk Approximation Test reference method" for iMLSb detection. |
2. Sample size used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective)
- Sample Size for Test Set:
- Clinical Study Isolates: Not explicitly stated as a single number for the entire test set. However, for the Phoenix Inducible Macrolide Resistance Test, the reported "CA (n)" is 295, indicating 295 isolates were used for this specific test within the clinical study.
- Site Reproducibility: A "panel of Gram-positive isolates" was used. Each site tested these isolates in triplicate on three different days. The exact number of isolates in this panel is not specified.
- Data Provenance: Clinical, stock, and challenge isolates were tested at multiple geographically diverse sites across the United States. The study type for clinical isolates was comparative against a reference method, which is typical for prospective data collection in such studies, though not explicitly stated. Challenge sets are typically retrospective (known results).
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience)
The document does not explicitly state the number of experts and their qualifications used to establish the ground truth for the test set. The ground truth for clinical isolates was established by comparing to the "CLSI reference broth microdilution method". For challenge isolates, results were compared to "expected results," implying a pre-defined ground truth. The interpretation of these reference methods would typically be performed by trained laboratory personnel, but no specific expert qualifications are provided.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set
The document does not describe any specific adjudication method (like 2+1 or 3+1) for resolving discrepancies in the test set. It mentions comparison to a reference method, suggesting that the reference method's result served as the definitive interpretation.
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 in the context of human readers with or without AI assistance. This device is an automated system (BD Phoenix Automated Microbiology System) for in vitro susceptibility testing, not an AI-assisted diagnostic tool that aids human interpretation of images or other data. The comparison is between the automated system and a reference laboratory method.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
Yes, this was a standalone performance study. The BD Phoenix Automated Microbiology System is an "algorithm only" type of device in the sense that it automatically performs the susceptibility testing and provides results (MIC values and category interpretations S, I, R, or N) without direct human interpretation within the measurement process itself. The study evaluates the performance of this automated system against reference methods.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc)
The primary type of ground truth used was:
- Reference Method Results: For clinical isolates, the "CLSI reference broth microdilution method" was used as the ground truth. This is a laboratory-based, standardized method considered the gold standard for antimicrobial susceptibility testing.
- Expected Results: For challenge isolates, "expected results" were used. This typically refers to isolates with well-characterized resistance profiles, often obtained from reference laboratories or collections.
8. The sample size for the training set
The document does not specify a separate "training set" for the BD Phoenix Automated Microbiology System in the context of this 510(k) submission. This is an antimicrobial susceptibility testing (AST) system; its "training" fundamentally involves the development and calibration of the instrument and its reagent panels to accurately detect bacterial growth and interpret MICs according to established microbiological principles and CLSI guidelines. The performance data presented (site reproducibility and clinical studies) is primarily for verification/validation.
9. How the ground truth for the training set was established
Since a distinct "training set" as understood in machine learning (where ground truth is typically assigned by experts for algorithm learning) is not explicitly mentioned or applicable in the traditional sense for this type of automated microbiology system, the method for establishing ground truth for a training set is not described. The system's underlying design and calibration would have relied on extensive microbiological knowledge and reference methods, ensuring its programmed interpretations align with CLSI standards.
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”