(45 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-Enteriaceae 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 rifampin at concentrations of 0.25-32 ug/mL to Gram Positive ID/AST or AST only Phoenix panels. Rifampin 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 Against:
Staphylococcus aureus (including Methicillin-Resistant/MRSA)
Staphylococcus epidermidis
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. 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 study information for the BD Phoenix™ Automated Microbiology System (Rifampin 0.25-32 µg/mL), based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are implied by the reported performance (Essential Agreement (EA) and Category Agreement (CA)) and the statement that the system demonstrated "substantially equivalent performance" compared to the NCCLS reference method as outlined in the FDA guidance document. While specific thresholds for EA and CA are not explicitly stated as "acceptance criteria" in a numerical table, the reported values indicate successful performance.
| Performance Metric | Acceptance Criteria (Implied by FDA Guidance) | Reported Device Performance (Rifampin) |
|---|---|---|
| Essential Agreement (EA) | Substantially equivalent to NCCLS reference method (typically acceptable if high agreement) | 98.3% (n=1261) |
| Category Agreement (CA) | Substantially equivalent to NCCLS reference method (typically acceptable if high agreement) | 98.2% (n=1261) |
| Intra-site Reproducibility | Greater than 90% | Greater than 90% |
| Inter-site Reproducibility | Greater than 95% | Greater than 95% |
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size: 1261 isolates were used for the clinical studies comparing Phoenix System results to reference methods for Rifampin. This sample size (n=1261) is specifically for the EA and CA percentages reported for Rifampin.
- Data Provenance: The isolates were "Clinical, stock and challenge isolates" tested "across multiple geographically diverse sites across the United States." This indicates a prospective and multi-center data collection approach.
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.
4. Adjudication Method for the Test Set
The document does not specify an adjudication method like 2+1 or 3+1. The ground truth for clinical isolates was established by the "NCCLS reference broth microdilution method." For challenge set isolates, it was compared to "expected results."
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
This is not an AI-assisted device for human interpretation; it is an automated microbiology system that provides direct results (MIC values and category interpretations). Therefore, an MRMC study comparing human readers with and without AI assistance is not applicable and was not performed.
6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) Was Done
Yes, a standalone performance evaluation was conducted. The BD Phoenix™ Automated Microbiology System operates as an automated system, generating results (ID, MIC, S/I/R categories) directly based on its internal algorithms and biochemical/turbidity readings. Its performance (EA and CA) was compared directly to a "reference method" (NCCLS broth microdilution), which represents its standalone accuracy.
7. The Type of Ground Truth Used
- For clinical isolates: The ground truth was established by the NCCLS reference broth microdilution method. This is a well-established and standardized laboratory method considered the gold standard for antimicrobial susceptibility testing.
- For challenge set isolates: The ground truth was based on "expected results."
8. The Sample Size for the Training Set
The document does not specify a sample size for a training set. This is typical for traditional (non-AI/machine learning) automated systems, where the "training" consists of developing and validating the underlying algorithms and biochemical reactions rather than training a machine learning model on a distinct dataset.
9. How the Ground Truth for the Training Set Was Established
Since there is no explicit mention of a "training set" in the context of machine learning, the concept of establishing ground truth for it is not applicable here. The fundamental principles and "ground truth" for the system's operation would be derived from general microbiological principles and extensive laboratory testing during the development of the assay and instrument.
§ 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.”