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VITEK 2 AST-Yeast Voriconazole 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 Voriconazole is a quantitative test. Voriconazole 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 krusei 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. The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique. 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 Voriconazole has the following concentrations in the card: 0.03125, 0.125, 0.25, 1, and 2 (equivalent standard method concentration by efficacy in ug/mL).

The provided FDA 510(k) summary describes the VITEK® 2 AST-Yeast Voriconazole device, which is an antimicrobial susceptibility test system.

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance:

The acceptance criteria are implicitly derived from the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems and are presented through "Essential Agreement" (EA) and "Category Agreement" (CA) performance metrics, along with error rates. The table below summarizes the reported performance for each microorganism. The specific acceptance thresholds for EA and CA are not explicitly stated as numerical percentages (e.g., >90% EA, >90% CA) with the exception of the individual error types (VME, ME, mE) having specified maximum allowable percentages. However, it is implied that the presented results were deemed acceptable by the FDA.

Key Definitions:

• Essential Agreement (EA): Agreement between the MIC results of the test device and the reference method within plus or minus one doubling dilution.
• Category Agreement (CA): Agreement between the interpretive categories (Susceptible, Intermediate, Resistant) of the test device and the reference method.
• Very Major Error (VME): The test device reports susceptible, but the reference method reports resistant.
• Major Error (ME): The test device reports resistant, but the reference method reports susceptible.
• Minor Error (mE): Any other disagreement in interpretive category (e.g., susceptible vs. intermediate, resistant vs. intermediate).

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

The sample sizes for the test set (external evaluation) are provided for each microorganism:

• C. albicans: 257 isolates
• C. krusei: 76 isolates
• C. parapsilosis: 74 isolates
• C. tropicalis: 87 isolates

Data Provenance: The study conducted an "external evaluation" with "fresh and stock clinical isolates, as well as a set of challenge strains." The document does not specify the country of origin of the data nor explicitly state if it was retrospective or prospective. However, "fresh clinical isolates" typically implies a prospective collection, while "stock clinical isolates" could be either.

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

The ground truth was established by the "CLSI broth microdilution reference method." This is a standardized laboratory method, not reliant on human expert adjudication in the same way an imaging study would be. Therefore, the concept of "experts" and their qualifications as typically applied to visual diagnostic tasks (e.g., radiologists) is not directly applicable here. The ground truth method itself (CLSI broth microdilution) is the expert-defined standard.

4. Adjudication Method for the Test Set:

Not applicable in the human expert sense. The "adjudication method" for determining the ground truth in this context is the CLSI broth microdilution reference method, which serves as the gold standard for antimicrobial susceptibility testing. The device's results are compared directly against this established reference.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done:

No, an MRMC comparative effectiveness study was not done. This type of study is relevant for diagnostic devices where human readers interpret results, often in conjunction with AI. The VITEK® 2 AST-Yeast Voriconazole is an automated in vitro diagnostic device for antimicrobial susceptibility testing; its performance is evaluated by comparing its automated output to a gold standard laboratory method, not by how it assists human readers.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done:

Yes, a standalone performance evaluation was done. The VITEK® 2 AST-Yeast Voriconazole system is an automated device designed to determine antimicrobial susceptibility without human interpretation of the primary data once the sample is loaded. The performance metrics (Essential Agreement, Category Agreement, error rates) directly reflect the device's standalone capability compared to the reference method.

7. The Type of Ground Truth Used:

The ground truth used was the CLSI broth microdilution reference method, incubated for 24 hours (up to 48 hours for slowly growing isolates). This is a well-established and scientifically accepted standard in microbiology for determining minimum inhibitory concentrations (MICs) of antifungal agents.

8. The Sample Size for the Training Set:

The document does not explicitly state the sample size for the training set. The descriptions focus on the "external evaluation" (test set). For IVD devices like this, the 'training set' often corresponds to historical data, internal studies, and method development efforts that lead to the final algorithm and concentration ranges. Without further information, the exact size of the training set used to develop the VITEK® 2 AST-Yeast Voriconazole algorithm is not provided in this 510(k) summary.

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

Similar to the answer for point 8, the document does not explicitly describe how the ground truth for any potential training set was established. However, given that the final performance is benchmarked against the CLSI broth microdilution reference method, it is highly probable that any internal development or training data would also have used this or a similar established reference method to determine the true susceptibility of isolates.

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