(49 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 the antimicrobial susceptibility of minute in the for Enterobacteriaceae and Non-Enterobacteriaceae Inculture analone bacteria isolates from pure culture belonging to the genera Staphylococcus, Enterococcus and Streptococcus.
This premarket notification is for cefazolin at concentrations of 0.5-32 µg/mL to Gram-negative ID/AST or AST only Phoenix panels with the removal of the limitations for Klebsiella oxytoca and Proteus mirabilis.
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°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).
This document describes the validation of the BD Phoenix™ Automated Microbiology System for Cefazolin (0.5-32 µg/mL) against Gram-negative bacteria, focusing on the removal of limitations for Klebsiella oxytoca and Proteus mirabilis.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are not explicitly stated with numerical targets for Essential Agreement (EA) and Category Agreement (CA) in the provided text. However, the study aims to demonstrate substantially equivalent performance when compared with the CLSI reference broth microdilution method, as defined in the FDA guidance "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems".
Based on common FDA guidance for AST systems, "substantial equivalence" often implies that the new system's performance (EA and CA) is non-inferior to and ideally very similar to the reference method. While specific thresholds are not provided in this excerpt, typical FDA expectations for AST devices often include:
- Essential Agreement (EA): Generally ≥ 90%
- Category Agreement (CA): Generally ≥ 90%
- Minor Errors (mE): Typically ≤ 7-10%
- Major Errors (ME): Typically ≤ 1.5-3%
- Very Major Errors (VME): Typically ≤ 1.5-3%
The provided Table 1 is incomplete and does not contain the actual performance data for Cefazolin. It is presented as:
| Antimicrobia | THE LEART THE FREE LER Concentration | 197 15 Carl College | 0 | 11 - A | 0 |
|---|---|---|---|---|---|
| Comments of Children and Children and Children and Sefazolın | e on 118/mr | 145 " Vall | OK | 1 0 P . . Vall | 05 |
Therefore, without the actual numerical data from Table 1, the device's reported performance against the acceptance criteria cannot be fully extracted from the provided text. The text does state that "The performance of the Phoenix System was assessed by calculating Essential Agreement (EA) and Category Agreement (CA) to expected/reference results for all isolates tested." and "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 as outlined in the FDA guidance document". This implies the device met the unstated acceptance criteria for substantial equivalence.
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size: The text mentions "Clinical, stock and challenge isolates were tested." No specific total number of isolates for the overall clinical study is provided. However, Table 1 (incomplete) shows a column with "197" which might refer to the number of isolates or a subset of them.
- Data Provenance: The data was collected from "multiple geographically diverse sites across the United States." The study included "Clinical, stock and challenge isolates." Clinical isolates are typically prospective or retrospectively collected real-world samples, while stock and challenge isolates are curated collections often used for specific performance assessments.
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 CLSI (formerly NCCLS) reference broth microdilution method. This is an established standard laboratory procedure, not an opinion-based expert consensus. Therefore, the concept of "number of experts" and their "qualifications" in the traditional sense of subjective interpretation (e.g., radiologists reading images) does not directly apply here. The "experts" would be the trained laboratory personnel who meticulously performed the CLSI reference method.
4. Adjudication Method for the Test Set
Not applicable. The ground truth was established by the CLSI reference broth microdilution method, which is an objective measurement, not a subjective interpretation requiring 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
No. This study is an evaluation of an automated AST system against a reference method, not a multi-reader multi-case study involving human readers with/without AI assistance. The device itself is an automated system for antimicrobial susceptibility testing.
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 an automated system, and its results were compared directly to the CLSI reference method. The device's performance is reported as its direct output (MIC values and categories S, I, R).
7. The Type of Ground Truth Used
The ground truth used was the CLSI reference broth microdilution method. This is a laboratory standard considered the gold standard for determining minimum inhibitory concentrations (MICs) and antimicrobial susceptibility categories. It represents a precise, objective, and well-established scientific method.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of machine learning or algorithm development. The study described focuses on the validation of the device's performance against reference methods. Automated microbiology systems typically use predefined algorithms and pre-calibrated reagents based on extensive prior development and internal testing, rather than a "training set" in the typical AI sense during the final validation for substantial equivalence submission. If there was an internal development phase, the sample size for that "training" would not be disclosed in this type of regulatory summary.
9. How the Ground Truth for the Training Set was Established
As no specific "training set" is mentioned in the context of this regulatory submission, this question cannot be answered from the provided text. The performance evaluation is against the CLSI reference broth microdilution method as the ground truth.
§ 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.”