(75 days)
The BD PhoenixTM 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-Enteriaceae 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 Moxifloxacin (0.125-8 ug/mL) and additional Gram-positive organism groups and Ciprofloxacin (0.25-4 ug/mL) and additional Gram-negative organism groups.
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 isolate, an inoculation 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 a breakdown of the acceptance criteria and the study details based on the provided document:
1. Table of Acceptance Criteria and Reported Device Performance:
The document refers to Essential Agreement (EA) and Category Agreement (CA) as metrics for performance. The acceptance criteria for these are implied by the FDA guidance document referenced, which typically requires high percentages. The reported performance for the BD Phoenix System is that it has "demonstrated substantially equivalent performance when compared to the CLSI reference broth microdilution method." Specifically, "Essential Agreement (EA) occurs when the BD Phoenix™ Automated Microbiology System agrees exactly or within + one two-fold dilution to the reference result. Category Agreement (CA) occurs when the BD Phoenix™ Automated Microbiology System agrees with the reference method with respect to the FDA categorical interpretive criteria (susceptible, intermediate, and resistant)."
While a precise numerical table of acceptance criteria and the exact reported performance for each drug/organism combination is not fully provided in the extract (the presented "Table 1" is fragmented and unreadable), the text states:
| Metric | Acceptance Criteria (Implied by FDA Guidance) | Reported Device Performance |
|---|---|---|
| Site Reproducibility (Intra-site) | >90% | >90% |
| Site Reproducibility (Inter-site) | >95% | >95% |
| Essential Agreement (EA) | Not explicitly stated in a percentage, but implied to be high for "substantial equivalence." EA occurs when the BD Phoenix™ Automated Microbiology System agrees exactly or within + one two-fold dilution to the reference result. | Demonstrated "substantially equivalent performance" when compared to the CLSI reference method. The excerpt from "Table 1" is unreadable but likely shows specific EA percentages for different organisms/drugs, indicating they met an internal or FDA-specified threshold for substantial equivalence. |
| Category Agreement (CA) | Not explicitly stated in a percentage, but implied to be high for "substantial equivalence." CA occurs when the BD Phoenix™ Automated Microbiology System agrees with the reference method with respect to the FDA categorical interpretive criteria (susceptible, intermediate, and resistant). | Demonstrated "substantially equivalent performance" when compared to the CLSI reference method. The excerpt from "Table 1" is unreadable but likely shows specific CA percentages for different organisms/drugs, indicating they met an internal or FDA-specified threshold for substantial equivalence. |
2. Sample Size Used for the Test Set and Data Provenance:
- Test Set Sample Size: The document mentions that isolates were tested, but it does not provide a specific numerical sample size for the test set (clinical, stock, and challenge isolates). "Table 1" would presumably contain this information, but it is unreadable.
- Data Provenance: The data was collected from multiple geographically diverse sites across the United States. The study included clinical, stock, and challenge isolates. This indicates a mix of prospective (new clinical isolates) and retrospective (stock and challenge isolates) data.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications:
- The ground truth for clinical isolates in the test set was established by the CLSI reference broth microdilution method. This is a standardized laboratory method, not typically performed by "experts" in the sense of physicians or radiologists making interpretations for AI.
- For challenge set isolates, the Phoenix System results were compared to "expected results." The document does not specify how these "expected results" were established or the number/qualifications of experts involved in determining them.
4. Adjudication Method for the Test Set:
- None directly applicable in the traditional sense. The ground truth for clinical isolates was the CLSI reference broth microdilution method, which is an objective measurement. For challenge isolates, it was "expected results," which would pre-exist. This isn't a scenario where multiple human readers are adjudicating a case.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done:
- No, an MRMC comparative effectiveness study was not done. This device is an automated laboratory instrument for antimicrobial susceptibility testing, not an imaging device or AI for human interpretation. Therefore, there is no "human readers improve with AI vs without AI assistance" component. The comparison is between the automated system and a reference lab 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 itself a standalone device (an "algorithm only," if you consider its integrated software for interpretation) that provides MIC values and categorical interpretations. Its performance was directly compared to the CLSI reference method.
7. The Type of Ground Truth Used:
- Reference Method/Standard Laboratory Procedure:
- For clinical isolates: CLSI reference broth microdilution method (AST panels prepared according to NCCLS M7).
- For challenge isolates: Expected results.
8. The Sample Size for the Training Set:
- The document does not explicitly mention a separate "training set" or its sample size. The "clinical studies" section describes data collected for performance evaluation, implying these isolates serve as the test set against the reference method. In the context of AST systems, the "training" (i.e., development and optimization) of the system's interpretive algorithms would typically involve extensive internal data, but this is not detailed in the summary.
9. How the Ground Truth for the Training Set Was Established:
- Since a distinct "training set" with established ground truth is not specified, this information cannot be provided from the given text. The development of such systems often relies on large internal datasets where ground truth is established using the same reference methods as the validation studies.
§ 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.”