(50 days)
The BD PhoenixTM 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 aztreonam at concentrations of 0.5-64 ug/mL to Gram-negative ID/AST or AST only Phoenix panels with the removal of the limitations for Pseudomonas aeruginosa, the removal of the truncation for Providencia stuartii and the addition of organism groups. Aztreonam 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:
Citrobacter species (including C. freundii)
Enterobacter species (including E. cloacae)
Escherichia coli
Klebsiella oxytoca
Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Serratia species (including S. marcescens)
Active In Vitro Against:
Aeromonas hydrophila
Morganella morganii
Proteus vulgaris
Providencia stuartii
Providencia rettgeri
Yersinia enterocolitica
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 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 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. Phoenix panels are inoculated with a specified organism density and placed in the instrument.
The instrument houses the panels where they are continuously incubated at a nominal temperature of 35℃. 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).
The BD Phoenix™ Automated Microbiology System for antimicrobial susceptibility testing of aztreonam was evaluated against the CLSI reference broth microdilution method.
Here's an analysis of the acceptance criteria and study details:
1. A table of acceptance criteria and the reported device performance:
| Performance Metric | Acceptance Criteria (Implicit from Guidance) | Reported Device Performance (Summary) |
|---|---|---|
| Site Reproducibility | ||
| Intra-site Reproducibility | > 90% | > 90% |
| Inter-site Reproducibility | > 95% | > 95% |
| Clinical Performance (Essential Agreement) | Substantially equivalent to reference method (implied high EA) | Not explicitly stated as a percentage, but essential agreement (EA) was calculated and deemed sufficient for substantial equivalence. The table of performance results is unreadable, but the conclusion states "data collected from the substantial equivalence studies demonstrate that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent." |
| Clinical Performance (Category Agreement) | Substantially equivalent to reference method (implied high CA) | Not explicitly stated as a percentage, but category agreement (CA) was calculated and deemed sufficient for substantial equivalence. The table of performance results is unreadable, but the conclusion states "data collected from the substantial equivalence studies demonstrate that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent." |
Note on Acceptance Criteria: The document refers to the FDA guidance document, "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA," February 5, 2003. This guidance document would contain the specific numerical acceptance criteria (e.g., minimum percentages for Essential Agreement and Category Agreement for different organism categories), which are not explicitly replicated in this 510(k) summary beyond the general statement of "substantially equivalent."
2. Sample sized used for the test set and the data provenance:
- Sample Size: The exact total number of isolates for the clinical studies (clinical, stock, and challenge isolates combined) is not explicitly stated as a single number. However, Table 1 (though unreadable) would have contained the specific counts for each organism and test type.
- Data Provenance:
- Country of Origin: United States. Isolates were tested "across multiple geographically diverse sites across the United States."
- Retrospective/Prospective: Not explicitly stated. However, "clinical isolates" are typically collected retrospectively or prospectively as part of routine clinical practice. "Stock" and "challenge" isolates are likely laboratory-curated.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- Number of Experts: Not applicable/not stated.
- Qualifications of Experts: This type of study (Antimicrobial Susceptibility Testing) does not rely on human experts to establish ground truth in the same way an imaging or diagnostic AI study would. The ground truth is established by a reference laboratory method (CLSI reference broth microdilution method) which is highly standardized and validated. The "experts" involved would be trained microbiologists following strict protocols.
4. Adjudication method for the test set:
- Adjudication Method: Not applicable. The ground truth is determined by a standardized reference method (CLSI broth microdilution). Discrepancies between the Phoenix System and the reference method are analyzed numerically (Essential Agreement and Category Agreement) rather than requiring expert adjudication.
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:
- MRMC Study: No, this was not an MRMC comparative effectiveness study involving human readers. This study evaluates the performance of an automated device (BD Phoenix System) against a reference laboratory method (CLSI broth microdilution) for determining antimicrobial susceptibility. It does not involve human interpretation or AI assistance in the context of human readers.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Standalone Performance: Yes, this was essentially a standalone performance study. The BD Phoenix™ Automated Microbiology System is an automated system (algorithm only) that provides MIC values and categorical interpretations (S, I, R) without direct human intervention in the interpretation process once the panel is loaded. Its performance was compared directly to the CLSI reference method.
7. The type of ground truth used:
- Ground Truth Type: Expert-established reference method. Specifically, the CLSI (formerly NCCLS) reference broth microdilution method was used as the ground truth for clinical isolates. For "challenge isolates," they were compared to "expected results," which would also be based on established reference methods or known phenotypic characteristics.
8. The sample size for the training set:
- Training Set Sample Size: The document does not explicitly state the sample size of a training set. For AST systems, the "training" (i.e., algorithm development and optimization) typically occurs during the initial development of the instrument and its interpretation algorithms using a large, diverse set of organisms with known susceptibility profiles. The data presented in this 510(k) summary are for validation/testing, not explicit "training" of a machine learning model as might be seen today.
9. How the ground truth for the training set was established:
- Training Set Ground Truth Establishment: Similar to the test set, the ground truth for any underlying development/training of the Phoenix system's interpretation algorithms would have been established using CLSI (or equivalent) reference broth microdilution methods. This is the gold standard for antimicrobial susceptibility testing.
§ 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.”