(70 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, Enterococcus, and Streptococcus.
This premarket notification is for additional Gram-negative organism groups and Cephalothin (1-64 ug/mL) on the BD Phoenix Automated Microbiology System.
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.
- t 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 into 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).
The BD Phoenix™ Automated Microbiology System for use with cephalothin (1-64 µg/mL) was studied to demonstrate its substantial equivalence to the CLSI reference broth microdilution method for antimicrobial susceptibility testing.
Here's an analysis of the acceptance criteria and the study that proves the device meets those criteria:
Acceptance Criteria and Reported Device Performance
The core acceptance criteria for the BD Phoenix™ Automated Microbiology System when compared to the CLSI reference broth microdilution method are Essential Agreement (EA) and Category Agreement (CA).
The document states:
"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."
Essential Agreement (EA) occurs when the BD Phoenix™ Automated Microbiology System agrees exactly or within ± one two-fold dilution to the reference result.
Category Agreement (CA) occurs when the BD Phoenix™ Automated Microbiology System agrees with the reference method with respect to the FDA categorical interpretive criteria (susceptible, intermediate, and resistant).
Unfortunately, "Table 1" which is supposed to summarize the performance, is illegible in the provided text. Therefore, the specific numerical values for EA and CA cannot be extracted. However, the conclusion states: "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 draft guidance document, 'Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA,' February 5, 2003." This implies that the reported performance (which would have been in the illegible Table 1) met the acceptance thresholds specified in that FDA guidance.
Table of Acceptance Criteria and Reported Device Performance:
| Acceptance Criteria | Reported Device Performance (from Table 1, assumed to meet criteria based on conclusion) |
|---|---|
| Essential Agreement (EA) | Specific value illegible in provided text. Assumed to meet FDA guidance. |
| Category Agreement (CA) | Specific value illegible in provided text. Assumed to meet FDA guidance. |
| Intra-site Reproducibility | > 90% |
| Inter-site Reproducibility | > 95% |
Sample Size and Data Provenance
Test Set Sample Size: The document mentions "clinical, stock and challenge isolates were tested." No specific total number of isolates for the test set is provided in the accessible text. However, the table of performance (Table 1) has a column that appears to be "Number of Isolates" but the values are also illegible.
Data Provenance: The study involved multiple geographically diverse sites across the United States. The data is prospective, testing the Phoenix System against the CLSI reference method.
Number of Experts and Qualifications for Ground Truth for Test Set
This section is not applicable in the context of this device. The ground truth for antimicrobial susceptibility testing (AST) is not established by human experts in the way, for example, a radiologist establishes ground truth for an image. Instead, the ground truth is established by a standardized, well-defined laboratory method: the CLSI reference broth microdilution method.
Adjudication Method for Test Set
This section is not applicable. As the ground truth is established by a standardized laboratory method (CLSI reference broth microdilution), there is no human adjudication process involved for determining the "correct" ground truth result.
Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, an MRMC comparative effectiveness study was not done. This type of study is typically performed for diagnostic devices where human interpretation plays a role (e.g., radiology AI). The BD Phoenix system is fully automated and does not involve human readers interpreting results in the same way. The comparison is between the automated system and a reference lab method.
Standalone Performance
Yes, a standalone performance study was done. The entire "Clinical Studies" section describes the performance of the Phoenix System by itself ("algorithm only," in this context meaning the automated system without human intervention influencing the result) compared to the CLSI reference method. The Essential Agreement (EA) and Category Agreement (CA) values discussed are metrics of this standalone performance.
Type of Ground Truth Used
The type of ground truth used is the CLSI reference broth microdilution method. This is a highly standardized and accepted laboratory method for determining antimicrobial minimal inhibitory concentrations (MICs) and categorical interpretations.
Sample Size for the Training Set
The document does not explicitly mention a "training set" or its sample size. This is common for this type of medical device at the time of its submission (2006). The BD Phoenix system uses pre-established algorithms based on known biochemical reactions and growth characteristics, rather than a machine learning model that would typically have a distinct training phase with a labeled dataset. The development likely involved extensive internal testing and optimization rather than a formal "training set" as understood in modern AI/ML development.
How the Ground Truth for the Training Set Was Established
As there is no distinct "training set" identified, this question is not applicable in the same way it would be for a typical AI/ML device. The underlying principles and mechanisms of the BD Phoenix system's interpretation are based on established microbiology principles and reference methods (like CLSI) that guide the determination of appropriate breakpoints and interpretive criteria.
§ 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.”