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VITEK® 2 AST-Yeast Fluconazole is designed for antifungal susceptibility testing of Candida species 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 antifungal agents. VITEK® 2 AST-Yeast Fluconazole is a quantitative test. Fluconazole has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antifungal.

Active in vitro and in clinical infections: Candida albicans Candida parapsilosis Candida tropicalis

The VITEK® 2 Fungal Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of clinically significant yeasts to antifungal agents when used as instructed.

The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh (1) and Gerlach (2). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique (3).

Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

VITEK® 2 AST-YS Fluconazole has the following concentrations in the card: 2, 4, 8, 16, 32, and 64 (equivalent standard method concentration by efficacy in us/mL).

Here's a breakdown of the acceptance criteria and study details for the VITEK® 2 AST-Yeast Fluconazole device, based on the provided document:

Acceptance Criteria and Device Performance

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VITEK® 2 Yeast Fluconazole is designed for antifungal susceptibility testing of Candida species. VITEK 2 Yeast Fluconazole is a quantitative test. It is intended for use with the VITEK 2 System as a laboratory aid in the determination of in vitro susceptibility to antifungal agents.

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

VITEK® 2 Yeast Fluconazole is designed for antifungal susceptibility testing of Candida species. It is intended for use with the VITEK 2 System as a laboratory aid in the determination of in vitro susceptibility to antifungal agents. The antifungal presented in the VITEK 2 AST Cards is in concentrations equivalent by efficacy to standard method concentrations in ug/ml. The VITEK 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) microdilution methodology.

The yeast isolate to be tested is diluted to a standardized concentration in 0.45% saline before being used to rehydrate the antifungal medium within the card. The VITEK 2 automatically fills, seals and places the card into the incubator/reader. The VITEK 2 monitors the growth of each well in the card over a defined period of time (up to 36 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 antifungal contained on the card.

Here's an analysis of the provided text regarding the VITEK® 2 Yeast Fluconazole device, focusing on acceptance criteria and study details:

1. Table of Acceptance Criteria and Reported Device Performance

Note: The specific numerical acceptance thresholds for "acceptable results" for reproducibility and quality control are not provided in the document. They are implicitly met if the "acceptable results" statement is considered sufficient by the FDA.

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

• Sample Size: Not explicitly stated as a number. The text mentions "fresh and stock clinical isolates and stock challenge strains." This suggests a diverse set of samples, but the exact count is not given.
• Data Provenance: The study was an "external evaluation." While the country of origin isn't specified, the submission is to the U.S. FDA, implying the data would be relevant to the U.S. context, potentially using U.S. strains or strains common in the U.S. It utilized both "fresh and stock clinical isolates," indicating a mix of prospective (fresh isolates) and retrospective (stock isolates) data.

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

Not applicable. The ground truth was not established by human experts in this context. It was established by a reference method.

4. Adjudication Method for the Test Set

Not applicable. The comparison was against a standardized reference method (CLSI), not against a consensus of human reviewers.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done

No, an MRMC comparative effectiveness study was not done. This device is an automated system for susceptibility testing, not an imaging device that requires human interpretation. The study focused on the agreement between the automated device and a reference laboratory method.

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

Yes, this was a standalone study. The VITEK® 2 system is an automated device designed to determine antifungal susceptibility without direct human interpretation of the primary result (i.e., the MIC value and interpretive category). The primary output is directly from the algorithm within the VITEK 2 system.

7. The Type of Ground Truth Used

The ground truth used was the Clinical and Laboratory Standards Institute (CLSI) reference method (specifically, the microdilution methodology). This is a standardized, laboratory-based method considered the gold standard for antimicrobial susceptibility testing.

8. The Sample Size for the Training Set

The document does not explicitly mention a "training set" or its sample size. This type of device relies on a pre-defined algorithm and comparison to a reference method, rather than a machine learning model that requires separate training, validation, and test sets. The "stock challenge strains" mentioned were likely used for verification or part of the external evaluation, not a distinct training phase in the machine learning sense.

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

Not applicable, as a distinct training set in the machine learning context is not described for this device. The development of the VITEK® 2 system's measurement capabilities would have relied on extensive testing and calibration against reference methods during its initial development.

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