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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

                                                                                                                                                                                                                                                                                                                              |

| Major Errors (ME) | Not explicitly stated as a numerical threshold, but ME are generally expected to be low, typically < 3%. | 3.0% (12/398) for Fluconazole overall. |
| Minor Errors (mE) | Not explicitly stated as a numerical threshold, but mE are generally expected to be low, typically < 10%. | 3.2% (14/442) for Fluconazole overall. |
| Reproducibility | "Acceptable results" | 100% Reproducibility reported for Fluconazole. (The table shows "%Reproducibility" column with "100" for Fluconazole, though the full context of this 100% isn't detailed in what "reproducibility" exactly refers to within this specific table line item). The text also states "Reproducibility and Quality Control demonstrated acceptable results." |

Note on Acceptance Criteria: While explicit numerical thresholds for EA, CA, VME, ME, and mE are not directly listed as "acceptance criteria" in the provided text, these metrics are standard for evaluating AST systems. The statement "VITEK® 2 AST-YS Fluconazole demonstrated acceptable performance" in conjunction with the reported percentages implies that these percentages met the required performance standards for substantial equivalence. The document references the "FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA (Issued August 28, 2009)," which would contain the specific performance criteria.

Study Details

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

   • Sample Size: The device performance table indicates a total of 442 isolates tested (denominator for EA and CA percentages). For VME analysis, 26 susceptible reference results (total) and for ME analysis, 398 instances (total, meaning the total population excluding those susceptible) were used. The number of Candida parapsilosis specific results cited are 14.
   • Data Provenance: The external evaluation was conducted with fresh and stock clinical isolates, as well as a set of challenge strains. The document does not specify the country of origin but implies clinical relevance. The study appears to be prospective or designed to simulate prospective use for evaluation, as it uses clinical and challenge strains. It is an "external evaluation," which typically means the testing was done at multiple sites.

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

   • Not Applicable. This is an in vitro diagnostic device for antimicrobial susceptibility testing. The ground truth is established by a reference laboratory method (CLSI broth microdilution), not by human experts. The "experts" in this context would be laboratory personnel meticulously performing the reference method.

3. Adjudication Method for the Test Set:

   • Not Applicable. As the ground truth is established by a quantitative laboratory method (CLSI broth microdilution), there is no human adjudication process involved for ambiguous interpretations. The comparison is directly between the MIC values and categorical interpretations (S, I, R) from the device and the reference method. Errors (VME, ME, mE) are calculated based on discrepancies from the reference method.

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

   • No. This is an in vitro diagnostic device, not an imaging or interpretive device that relies on human readers. Therefore, an MRMC study is not relevant or performed for this type of product. The "readers" are the automated VITEK® 2 systems themselves.

5. Standalone (Algorithm-Only) Performance:

   • Yes. The study evaluates the performance of the VITEK® 2 AST-YS Fluconazole device in conjunction with the VITEK® 2 and VITEK® 2 Compact Systems. This is a standalone evaluation of the integrated system (test card + instrument + embedded analysis algorithms) against the CLSI reference method, without a human in the loop for interpretation of the raw data generated by the system. The system automatically generates the MIC value and interpretive category.

6. Type of Ground Truth Used:

   • CLSI broth microdilution reference method. This is a universally accepted, gold standard laboratory method for determining minimum inhibitory concentrations (MICs) of antifungal agents. The reference method was incubated at 24 hours (or up to 48 hours for isolates with slow growth).

7. Sample Size for the Training Set:

   • Not explicitly stated in the provided document. The document details the "Premarket Notification (Special 510[k]) presents data in support of VITEK® 2 AST-YS Fluconazole." This implies that the data presented here is for the validation or test set, used to demonstrate substantial equivalence. The VITEK® 2 system's "Discriminant Analysis" algorithms would have been developed and refined (trained) on prior datasets, but the size and nature of those training sets are not part of this 510(k) summary. These types of devices often use extensive historical isolate collections for algorithm development.

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

   • Not explicitly stated in the provided document for the training set. However, given the nature of the device and the reference method used for the test set, it is highly probable that the ground truth for any training sets used for the "Discriminant Analysis" algorithms would also have been established via the CLSI broth microdilution reference method or similar established laboratory methods.

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