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VITEK® 2 Gram Negative Ceftazidime/Avibactam is designed for antimicrobial susceptibility testing of Gram negative bacilli and is intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. VITEK® 2 Gram Negative Ceftazidime/ Avibactam is a quantitative test. Ceftazidime/Avibactam has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active both in vitro and in clinical infections:

Citrobacter freundii Enterobacter cloacae Escherichia coli Klebsiella oxytoca Klebsiella pneumoniae Proteus mirabilis Pseudomonas aeruginosa

The following in vitro data are available, but clinical significance is unknown:

Citrobacter koseri Enterobacter aerogenes Morganella morganii Providencia stuartii Serratia marcescens

The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 Systems for the automated quantitative or qualitative susceptibility testing of isolated colonies for the most clinically significant aerobic gram-negative bacilli, Staphylococcus spp., Streptococcus spp., Streptococcus spp. and clinically significant yeast.

The VITEK® 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) microdilution methodology.

The isolate to be tested is diluted to a standardized concentration in 0.45 - 0.50% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling and sealing operation. The VITEK® 2 monitors the growth of each well in the card over a defined period of time (up to 18 hours). At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antimicrobial contained on the card.

Here's a breakdown of the acceptance criteria and study details for the VITEK® 2 AST-GN Ceftazidime/Avibactam device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

Note: The specific numerical targets for Essential Agreement, Category Agreement, and Major Error Rate are not explicitly stated as "acceptance criteria" percentages in the document, but rather "acceptable performance" is implied by the reported percentages, which are compared against general guidance for AST systems. The document states that the device "demonstrated substantially equivalent performance when compared with the CLSI broth microdilution reference method, as defined in the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems: Guidance for Industry and FDA (Issued August 28, 2009)." This suggests compliance with the performance metrics outlined in that guidance.

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

• Sample Size:
  • The document implies a sample size for the major error rate calculation: 998 strains.
  • It mentions "fresh and stock clinical isolates, as well as a set of challenge strains." The exact total number of isolates tested for overall performance (EA and CA) is not explicitly stated, but based on the major error calculation for 998 strains, it's at least that number or more for the full evaluation.
• Data Provenance: Not explicitly stated (e.g., specific countries). However, the use of "clinical isolates" suggests a real-world collection, and "challenge strains" implies some curated, potentially reference or difficult-to-test strains. The study is retrospective in the sense that these are collected isolates being tested.

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

This information is not provided in the document. The ground truth is established by the CLSI broth microdilution reference method, which is a standardized laboratory procedure, not an expert panel.

4. Adjudication Method for the Test Set

This information is not applicable as the ground truth is established by the CLSI broth microdilution reference method, not through expert consensus requiring adjudication. The major error rate calculation describes an adjustment based on how close the errors were to the reference method (within one dilution), but this is a statistical adjustment, not an expert adjudication process.

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 done.
• This device is an automated antimicrobial susceptibility testing (AST) system. Its purpose is to automate the determination of susceptibility, not to assist human readers in interpreting images or other data. The "readers" here are the VITEK® 2 systems themselves, interpreting growth in wells.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done

• Yes, this was a standalone performance study of the VITEK® 2 AST-GN Ceftazidime/Avibactam system.
• The system is the algorithm (or rather, the automated process) that determines susceptibility based on growth patterns in the card wells. Its performance was compared directly against the reference method without human intervention in the interpretation process of the device results.

7. The Type of Ground Truth Used

• The ground truth used was the CLSI broth microdilution reference method. This is a laboratory-established standard for determining minimum inhibitory concentrations (MICs) of antimicrobial agents.

8. The Sample Size for the Training Set

• The document does not provide a sample size for a training set. This is because the VITEK® 2 system, while automated, is likely based on established principles of growth detection and does not typically involve a "training set" in the machine learning sense to learn a new classification model during development for each new antimicrobial/organism combination. Instead, performance is validated against a reference method.

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

• As there's no explicit training set in the machine learning sense mentioned, this question is not applicable. The ground truth for the validation or test set was established by the CLSI broth microdilution reference method.

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