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VITEK® 2 AST-Gram Negative Tigeovcline 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 AST-Gram Negative Tigecycline is a quantitative test. Tigecycline has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active in vitro and in clinical infections: Citrobacter freundii Enterobacter cloacae Escherichia coli Klebsiella oxytoca Klebsiella pneumonia

In vitro data available but clinical significance is unknown: Citrobacter koseri Enterobacter aerogenes 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, Staphylococus spp., Enterococcus 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.

The VITEK 2 AST-GN Tigecycline device is an automated system for antimicrobial susceptibility testing of Gram-negative bacilli. The study assessed its performance against the CLSI broth microdilution reference method.

1. Acceptance Criteria and Reported Device Performance:

The primary performance metrics for this device are Essential Agreement (EA) and Category Agreement (CA) when compared to the CLSI broth microdilution reference method. The acceptance criteria are not explicitly stated as numerical targets in the provided text but are implied by the reported "acceptable performance."

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

The document states an "external evaluation was conducted with fresh and stock clinical isolates, as well as a set of challenge strains." However, the specific numerical sample size for the test set is not provided in the given text.

The data provenance is from an "external evaluation," and it involved "clinical isolates" and "challenge strains," suggesting a mix of retrospective (stock clinical isolates, challenge strains) and potentially prospective (fresh clinical isolates) data. The country of origin of the data is not specified.

3. Number of Experts and Qualifications for Ground Truth:

The document mentions that the performance of the VITEK 2 AST-GN Tigecycline was compared with the CLSI broth microdilution reference method. This method itself serves as the 'ground truth.' It is a standardized laboratory procedure, not typically established by individual experts but rather by a consensus of scientific and medical professionals who develop the CLSI (Clinical and Laboratory Standards Institute) guidelines. Therefore, the concept of "number of experts used to establish the ground truth" in the traditional sense of expert consensus on images or diagnoses does not apply here. The ground truth is the result produced by the CLSI reference method.

4. Adjudication Method:

Since the ground truth is established by a standardized laboratory reference method (CLSI broth microdilution), there is no adjudication method described or necessary in the typical sense (e.g., 2+1, 3+1). The VITEK 2 results are directly compared to the output of the reference method.

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

A Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This device is an automated system for susceptibility testing, not an imaging or diagnostic device that requires human interpretation. Therefore, there is no "human readers improve with AI vs without AI assistance" component.

6. Standalone Performance:

Yes, a standalone performance evaluation was done. The study directly compared the performance of the algorithm only (VITEK 2 AST-GN Tigecycline system) to the CLSI broth microdilution reference method. The reported Essential Agreement and Category Agreement percentages represent the device's standalone performance.

7. Type of Ground Truth Used:

The ground truth used was the CLSI broth microdilution reference method, which is a standardized and widely accepted laboratory procedure for determining antimicrobial minimum inhibitory concentrations (MICs).

8. Sample Size for the Training Set:

The document does not specify the sample size used for the training set. It only describes the "external evaluation" for performance assessment.

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

The document does not provide information on how the ground truth for any potential training set was established. Given the nature of an automated system, it is likely that internal development and validation would involve similar reference methods to establish ground truth for training, but this is not explicitly stated.

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