(211 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 anacrobic 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 confirmatory ESBL Test to Gram-negative ID/AST or AST only Phoenix panels. The Phoenix confirmatory ESBL Test is a confirmatory test for the detection of the organisms that produce extended spectrum 3-lactamses (ESBL) in Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca.
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 an analysis of the provided text, outlining the acceptance criteria and study details:
Acceptance Criteria and Device Performance for BD Phoenix™ Automated Microbiology System - confirmatory ESBL Test (K033458)
1. Table of Acceptance Criteria and Reported Device Performance
| Performance Metric | Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|---|
| Overall Percent Agreement | Not explicitly stated, but typically >90% for AST devices to demonstrate substantial equivalence. | 96.2% |
| Positive Percent Agreement (PPA) | Not explicitly stated, but typically >90%. | 96.8% |
| Negative Percent Agreement (NPA) | Not explicitly stated, but typically >90%. | 96.1% |
| Intra-site Reproducibility | >90% | >90% |
| Inter-site Reproducibility | >95% | >95% |
Note: The acceptance criteria for the agreement percentages (Overall, Positive, Negative) are not explicitly stated as numerical targets in the provided text. However, for a 510(k) submission to demonstrate substantial equivalence, agreement percentages typically need to be high (e.g., often >90%) when compared to a reference method, which the reported performance meets.
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size:
- Clinical Isolates: The exact number of clinical isolates is not specifically provided, but they were collected across multiple geographically diverse sites across the United States.
- Challenge Isolates: 30 previously characterized challenge organisms were tested at one site. The total number of challenge isolates contributing to the agreement percentages is not explicitly stated beyond these 30, but the overall results involved 1001 tests (963 agreement / 1001 total). It's reasonable to infer that the 1001 tests comprised a combination of clinical and challenge isolates.
- Reproducibility Test: "a panel of Gram-negative isolates" tested in triplicate on three different days. Specific number not provided, but at "three sites".
- Data Provenance: Retrospective and Prospective.
- Clinical Isolates: Compared to concurrent testing in the NCCLS reference broth microdilution method. This implies prospective collection or concurrent testing within the study. "Clinical, stock and challenge isolates were tested across multiple geographically diverse sites across the United States."
- Challenge Isolates: These were "previously characterized organisms" (retrospective characterization), but the testing with the Phoenix system was likely prospective within the study.
- Site Reproducibility: Likely prospective testing conducted specifically for the study.
- Overall: The data came from "multiple geographically diverse sites across the United States."
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
- The ground truth for the test set was established by the NCCLS reference broth microdilution method rather than human expert consensus for clinical isolates.
- For Challenge organisms, the "expected results" acted as the ground truth. The process for generating these "expected results" is described as "previously characterized," suggesting prior microbiological expert determination or established methods.
- No information is provided about the number of human experts or their specific qualifications (e.g., microbiologists, lab technologists) involved in performing the NCCLS reference method or characterizing the challenge organisms, as these methods themselves are the gold standard.
4. Adjudication Method for the Test Set
- None in the traditional sense of multiple human readers resolving discrepancies.
- The comparison was directly between the BD Phoenix™ Automated Microbiology System's results and the results obtained from the NCCLS reference broth microdilution method (for clinical isolates) or "expected results" (for challenge isolates). Any discrepancies would presumably be analyzed against the reference standard.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
- No, an MRMC comparative effectiveness study was not performed. This device is an automated antimicrobial susceptibility test system, not an imaging or diagnostic AI system designed to assist human readers. Therefore, the concept of improving human reader performance with AI assistance does not apply.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
- Yes, a standalone performance evaluation was done. The entire study evaluates the performance of the BD Phoenix™ Automated Microbiology System (an automated algorithm/device) directly against a reference method without any human interpretation of the Phoenix system's output needing to be part of the "performance" calculation for the device itself. Human operators perform the initial sample preparation and load the panels, but the interpretation and results are generated automatically by the system.
7. The Type of Ground Truth Used
- Reference standard/method:
- For clinical isolates: NCCLS reference broth microdilution method.
- For challenge isolates: "Expected results" based on "previously characterized organisms," implying a highly reliable characterization method often considered a gold standard in microbiology.
8. The Sample Size for the Training Set
- Not explicitly stated within the provided text. The document focuses on the validation or performance studies for this specific confirmatory ESBL test addition. While it mentions the general BD Phoenix system has demonstrated equivalence previously, details about its initial training data are not included in this 510(k) summary for the ESBL test.
9. How the Ground Truth for the Training Set Was Established
- Not applicable / Information not provided. Since the sample size for the training set is not mentioned, the method for establishing its ground truth is also not available in this document. Given the device's nature (automated testing using dried reagents and redox indicators), "training" might involve calibration and optimization against established reference strains and methods rather than a distinct "training set" in the machine learning sense. The summary focuses on the validation of the ESBL test's performance.
§ 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.”