(105 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 additional Gram-negative organism groups and Gatifloxacin (0.25-8 ug/mL) on the BD Phoenix Automated Microbiology System. Gatifloxacin 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.
Active In Vitro and in Clinical Infections Against:
Aerobic Gram-negative microorganisms Escherichia coli Klebsiella pneumoniae Proteus mirabilis
Active In Vitro Against:
Aerobic Gram-negative microorganisms Acinetobacter lwoffii Citrobacter koseri Citrobacter freundii Enterobacter aerogenes Enterobacter cloacae Klebsiella oxytoca Morganella morganii Proteus vulgaris
Results for Enterobacteriaceae tested with Gatifloxacin should only be reported for isolates recovered from the urinary tract.
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 . for 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 polystyrene 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. For each isolation equivalent to a 0.5 McFarland standard is prepared in Phoenix ID Broth.
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. 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 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, or R (sensitive, intermediate, or resistant).
Here's an analysis of the provided text, focusing on the acceptance criteria and the study proving the device meets them:
Acceptance Criteria and Device Performance
| Acceptance Criteria Description | Reported Device Performance |
|---|---|
| Site Reproducibility: Overall intra-site reproducibility > 90% for each antimicrobial agent. | Result: Overall intra-site reproducibility > 90% for the isolates tested. |
| Site Reproducibility: Overall inter-site reproducibility > 95% for each antimicrobial agent. | Result: Overall inter-site reproducibility > 95% for the isolates tested. |
| Clinical Performance (Essential Agreement - EA): Performance of BD Phoenix System should demonstrate Essential Agreement to expected/reference results. (Though not explicitly stated as a numerical threshold, the context implies a high level of agreement is necessary for "substantial equivalence"). | Result: Gatifloxacin GN: 98.8% Essential Agreement (n=2213) |
| Clinical Performance (Category Agreement - CA): Performance of BD Phoenix System should demonstrate Category Agreement to expected/reference results. (Similar to EA, a high level of agreement is implied for "substantial equivalence"). | Result: Gatifloxacin GN: 95.8% Category Agreement (n=2213) |
| Substantial Equivalence: Performance equivalent to CLSI reference broth microdilution method and guidance outlined in "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA," February 5, 2003. | Result: "The data collected from the substantial equivalence studies demonstrate that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent..." |
Study Details
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Sample sizes used for the test set and the data provenance:
- Test Set Sample Size: 2213 isolates for Gatifloxacin GN (Gram-Negative).
- Data Provenance: Clinical, stock, and challenge isolates were tested. The studies were conducted across "multiple geographically diverse sites across the United States." This indicates the data is retrospective as it uses existing isolates, but the testing itself would be prospective with these isolates.
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Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- The document does not specify the number or qualifications of experts used to establish the ground truth. It states that Phoenix System results for clinical isolates were compared to "results obtained from the CLSI reference broth microdilution method," which is a standardized laboratory method. For "Challenge set isolates," they were compared to "expected results." This implies the ground truth is derived from established laboratory protocols and potentially expert determination for the challenge set, but no specific expert involvement is detailed.
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Adjudication method (e.g., 2+1, 3+1, none) for the test set:
- The document does not explicitly mention an adjudication method for the test set. The comparison is made against a "CLSI reference broth microdilution method" or "expected results," which are typically objective laboratory findings or pre-defined results for challenge isolates, not usually subject to human adjudication in the same way, for example, a medical imaging interpretation might be.
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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. This is not an MRMC study. The device (BD Phoenix™ Automated Microbiology System) is an automated system for antimicrobial susceptibility testing, which directly provides an output (MIC values and category interpretations: S, I, or R). It is not an AI-assisted diagnostic tool designed to be used by human readers for interpretation. Therefore, the concept of "human readers improve with AI vs without AI assistance" does not apply to this type of device.
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If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:
- Yes. The study describes the performance of the "BD Phoenix™ Automated Microbiology System" itself, against a reference method. The system is designed to provide results automatically ("Phoenix AST method is a broth based microdilution test. The Phoenix System utilizes a redox indicator for the detection of organism growth... Measurements of changes to the indicator as well as bacterial turbidity are used... The instrument takes readings of the panels every 20 minutes. The readings are interpreted to give an identification..."). This is a standalone performance evaluation of the automated algorithm.
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The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
- The ground truth used was the CLSI reference broth microdilution method for clinical isolates, and "expected results" for challenge isolates. This is a laboratory-based, standardized reference method considered the gold standard for antimicrobial susceptibility testing.
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The sample size for the training set:
- The document does not specify a sample size for a training set. The description implies that the system's underlying methodology for determining AST (redox indicator, bacterial turbidity measurements) is inherent to its design and based on established microbiological principles, rather than being "trained" in the typical machine learning sense with a distinct training dataset. The studies described are performance validation studies.
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How the ground truth for the training set was established:
- As there is no mention of a traditional "training set" in the context of machine learning, the question of how ground truth for it was established is not directly applicable. The device's operation is based on physicochemical measurements and pre-programmed interpretations adhering to microbiological 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.”