(47 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 and Enterococcus.
This premarket notification is for the addition of the antimicrobial agents gentamicin synergy at a concentration of 500 ug/mL and streptomycin synergy at a concentration of 1000 ug/mL to Gram Positive ID/AST or AST only Phoenix panels. Gentamicin synergy and streptomycin synergy are used to predict synergy between ampicillin, penicillin or vancomycin and an aminoglycoside with enterococci.
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 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, 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 twofold 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, outlining the acceptance criteria and study details for the BD Phoenix™ Automated Microbiology System for Gentamicin Synergy and Streptomycin Synergy.
1. Table of Acceptance Criteria and Reported Device Performance
The text explicitly compares the BD Phoenix System's performance to the NCCLS reference broth microdilution method. While the document doesn't present a formal "acceptance criteria" table with pre-defined thresholds, it implicitly uses the concept of "substantially equivalent performance" to the reference method. The reported performance is as follows:
| Antimicrobial | Performance Metric | Reported Value | Implicit Acceptance Criteria (based on "substantially equivalent performance") |
|---|---|---|---|
| Gentamicin Synergy | Overall Agreement (CA)% * | 98.6% | Based on the FDA Draft guidance document, "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices", March 8, 2000, which defines criteria for "substantially equivalent." |
| Streptomycin Synergy | Overall Agreement (CA)% * | 97.8% | Based on the FDA Draft guidance document, "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices", March 8, 2000, which defines criteria for "substantially equivalent." |
| Gentamicin Synergy | Essential Agreement (EA)% * | -- | Expected to be high, but not explicitly stated for this particular antimicrobial in the table. |
| Streptomycin Synergy | Essential Agreement (EA)% * | -- | Expected to be high, but not explicitly stated for this particular antimicrobial in the table. |
| Intra-site Reproducibility | >90% | >90% | |
| Inter-site Reproducibility | >95% | >95% |
Note: The document uses "CA%" (Category Agreement) as the primary reported metric in Table 1 for both Gentamicin Synergy and Streptomycin Synergy. "EA%" (Essential Agreement) is listed in the table header but no values are provided for these specific agents in this summary.
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size:
- Gentamicin Synergy: 763 isolates (for Category Agreement)
- Streptomycin Synergy: 756 isolates (for Category Agreement)
- Reproducibility study: "a panel of Gram-positive isolates" (exact number not specified beyond "panel")
- Data Provenance: Clinical, stock, and challenge isolates were tested across multiple geographically diverse sites across the United States. This indicates a prospective collection and testing approach and data from the United States.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not mention the use of experts to establish ground truth for the test set. Instead, the ground truth was established by comparison to a reference method.
4. Adjudication Method for the Test Set
The document does not describe an adjudication method involving experts for discrepancies. The comparison is made directly with the NCCLS reference broth microdilution 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, an MRMC comparative effectiveness study was not done.
- This device is an automated system for antimicrobial susceptibility testing, not an AI-assisted diagnostic tool that human readers would use. Therefore, the concept of human readers improving with AI assistance is not applicable in this context.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done
- Yes, a standalone performance study was done. The entire study evaluates the performance of the "BD Phoenix™ Automated Microbiology System" (an automated device/algorithm) against a reference method without human interpretation of the system's raw output. The system produces MIC values and S, I, or R interpretations directly.
7. The Type of Ground Truth Used
The ground truth used for the clinical studies was the NCCLS reference broth microdilution method. For challenge isolates, the ground truth was "expected results."
8. The Sample Size for the Training Set
The document does not provide information regarding a separate "training set" or its sample size. This is typical for traditional in vitro diagnostic devices where the "training" (development and validation of the algorithms and reagents) likely happened iteratively with internal data and was robust prior to formal clinical validation described here.
9. How the Ground Truth for the Training Set Was Established
Since no specific "training set" is mentioned, the method for establishing its ground truth is also not described. However, it can be inferred that developers would use similar reference methods (like NCCLS broth microdilution) to establish the ground truth for any data used during the development and optimization phases of the device.
§ 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.”