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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.

This premarket notification is for the addition of the antimicrobial agent cefepime at concentrations of 0.0625-4 ug/mL to Streptococcus ID/AST or AST only Phoenix panels. Cefepime has been shown to be active in virro 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:

Streptococcus pneumoniae
Streptococcus pyogenes (Lancefield's Group A streptococci)
Viridans group streptococci

Active In Vitro Against:

Streptococcus agalactiae (Lancefield's Group B streptococci)

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. For testing Streptococcus species 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-S Broth used for performing AST tests only. .
• BD Phoenix AST-S 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, R or N (susceptible, intermediate, resistant or not susceptible).

Here's an analysis of the acceptance criteria and the study that proves the device meets them, based on the provided text:

Device: BD Phoenix™ Automated Microbiology System - Cefepime 0.0625-4 µg/mL

1. Table of Acceptance Criteria and Reported Device Performance

Note: The document implicitly defines these performance metrics as the acceptance criteria by stating that the system demonstrated "substantially equivalent performance" by meeting these figures when compared to the CLSI reference method, as outlined in the FDA draft guidance document.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size (n): 1890 isolates. This refers to the combined number of clinical, stock, and challenge isolates used for the Essential Agreement (EA) and Category Agreement (CA) calculations for Cefepime.
• Data Provenance: The data was collected from "multiple geographically diverse sites across the United States." The isolates included:
  • Clinical isolates: Used for comparison to the CLSI reference broth microdilution method.
  • Stock isolates: Not explicitly detailed how they were used, but implied in the overall "isolates tested."
  • Challenge isolates: Compared to "expected results."
  • The study is prospective in nature as it details performance testing of the device against reference methods.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications

The document does not explicitly state the number of experts or their qualifications for establishing the ground truth.

However, the ground truth was established by:

• CLSI reference broth microdilution method: This is a standardized laboratory method, and the interpretation would typically be performed by trained microbiologists or laboratory personnel following CLSI guidelines. The expertise lies in adherence to a standardized protocol rather than individual experts' subjective assessment.
• "Expected results" for Challenge set isolates: This implies pre-established results for a known set of organisms, likely determined by expert consensus or established reference methods prior to the study.

4. Adjudication Method for the Test Set

The document does not explicitly describe an adjudication method (e.g., 2+1, 3+1).

The primary comparison was between the BD Phoenix™ System results and established reference methods (CLSI reference broth microdilution or "expected results" for challenge isolates). Discrepancies would likely be analyzed based on the defined agreement criteria (EA and CA) rather than through a separate expert adjudication process for each individual case.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done.

This type of study typically involves multiple human readers interpreting cases with and without AI assistance to measure the effect size of AI on human performance. The BD Phoenix™ Automated Microbiology System is an automated device designed to perform antimicrobial susceptibility testing; it does not involve human readers in the interpretation process in the way medical imaging AI might. The comparison here is between the automated system's output and a reference laboratory method.

6. Standalone Performance

Yes, a standalone performance study was done.

The entire study described is a standalone performance evaluation of the BD Phoenix™ Automated Microbiology System. It evaluates the algorithm's (device's) ability to correctly determine MIC values and categorical interpretations (S, I, R, N) without human intervention in the interpretation flow. The results (EA and CA percentages) directly reflect the algorithm-only performance against a reference standard.

7. Type of Ground Truth Used

The primary ground truth used was:

• Reference Standard Data:
  • CLSI (Clinical and Laboratory Standards Institute) reference broth microdilution method: This is a widely accepted laboratory standard for antimicrobial susceptibility testing.
  • "Expected results" for Challenge set isolates: These represent predetermined or known results for a panel of bacterial isolates, likely established through extensive testing with reference methods or expert consensus.

8. Sample Size for the Training Set

The document does not provide information regarding the sample size for the training set. This information is typically proprietary to the manufacturer and not usually included in 510(k) summaries, which focus on validation studies for regulatory approval.

9. How the Ground Truth for the Training Set Was Established

The document does not provide information on how the ground truth for the training set was established, as it does not discuss the training process of the device.

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