(59 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 agent ampicillin at concentrations of 0.5-32 ug/mL to Gram-negative ID/AST or AST only Phoenix panels. ampicillin 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:
Escherichia coli Proteus mirabilis Salmonella species Shigella species
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 isolation 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 regarding the acceptance criteria and study for the BD Phoenix™ Automated Microbiology System with Ampicillin:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are not explicitly stated as numerical targets in a formal "acceptance criteria" section. Instead, the document frames "substantial equivalency" as the overarching goal, which is demonstrated by achieving high Essential Agreement (EA) and Category Agreement (CA) to a recognized reference method (NCCLS microdilution). The FDA's issuance of a substantial equivalence determination letter further validates this.
However, based on the performance table, the implicit acceptance criteria would be for EA and CA to be very high, likely exceeding 90% as seen in the reported results.
| Metric | Acceptance Criteria (Implicit) | Reported Device Performance (Ampicillin) |
|---|---|---|
| Essential Agreement (EA) | High (e.g., >90%) | 98.1% (n=838) |
| Category Agreement (CA) | High (e.g., >90%) | 98.3% (n=838) |
| Intra-site Reproducibility | >90% | >90% |
| Inter-site Reproducibility | >95% | >95% |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Test Set: 838 isolates for the Ampicillin performance evaluation. This includes "Clinical, stock and challenge isolates."
- Data Provenance: The study was conducted "across multiple geographically diverse sites across the United States." The data is a mix of prospective (clinical isolates) and retrospective (stock and challenge isolates) from various sources.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not specify the number or qualifications of experts used to establish the ground truth. It states that for clinical isolates, the Phoenix System results were compared to the NCCLS reference broth microdilution method. For challenge set isolates, they were compared to "expected results." This implies reliance on established laboratory standards and expected antimicrobial susceptibility patterns rather than individual expert adjudication of each case.
4. Adjudication Method for the Test Set
The document describes comparing the Phoenix System results to:
- NCCLS reference broth microdilution method for clinical isolates.
- Expected results for challenge set isolates.
This indicates a comparison against a reference standard rather than an adjudication process involving multiple human readers for each case. The "adjudication" (or determination of correctness) is against the established NCCLS method for clinical strains and pre-determined 'expected results' for challenge strains. There is no mention of physician or clinical expert adjudication on specific cases.
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 involving human readers and AI assistance was not conducted. This device is an automated microbiology system that performs AST and ID, not an AI-assisted diagnostic tool for human interpretation. 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, a standalone performance study was done. The entire evaluation is focused on the performance of the "BD Phoenix™ Automated Microbiology System" (an automated algorithm/device) against a reference standard (NCCLS broth microdilution method) without human interpretation as part of the primary outcome assessment. The system itself determines the MIC values and categorical interpretations (S, I, R).
7. The Type of Ground Truth Used
The ground truth used was:
- NCCLS reference broth microdilution method: for clinical isolates. This is a recognized laboratory standard for antimicrobial susceptibility testing.
- Expected results: for challenge set isolates. These are pre-determined or known susceptibility profiles for specific strains.
8. The Sample Size for the Training Set
The document does not provide any information regarding a specific training set size or methodology. The description focuses on the evaluation (test) set. Given this is an automated system developed prior to the widespread use of deep learning, it's more likely that the system's underlying rules and algorithms were developed based on extensive microbiology knowledge and earlier data, rather than a distinct "training set" in the modern machine learning sense. The "clinical, stock, and challenge" isolates mentioned appear to be solely for evaluating the performance of the established system against a reference, not for training it.
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.
§ 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.”