(41 days)
VITEK® 2 Gram Positive Cefoxitin Screen is a qualitative test designed to predict mecAmediated resistance in staphylococci. It 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.
The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 and VITEK® 2 Compact Systems for the automated quantitative or qualitative susceptibility testing of isolated colonies for the most clinically significant aerobic gramnegative bacilli, Staphylococcus spp., Enterococcus spp., Streptococcus agalactiae, and S. pneumoniae.
The VITEK 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) microdilution methodology. The bacterial isolate to be tested is diluted to a standardized concentration in 0.45% 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. For the VITEK 2 Cefoxitin Screen the report will list either a positive or negative test result.
The provided text describes the VITEK® 2 Gram Positive Cefoxitin Screen, a qualitative test designed to predict mecA-mediated resistance in staphylococci. Below is an analysis of its acceptance criteria and the study conducted.
1. Table of Acceptance Criteria and Reported Device Performance
| Criteria | Acceptance Threshold | Reported Device Performance |
|---|---|---|
| Overall Category Agreement (vs. CLSI) | Not explicitly stated as a numerical threshold, but implies "acceptable" performance for substantial equivalence. | 97.2% overall Category Agreement |
| Reproducibility | "acceptable results" (implied, not quantified) | Demonstrated acceptable results |
| Quality Control | "acceptable results" (implied, not quantified) | Demonstrated acceptable results |
| Substantial Equivalence with Predicate | Demonstrated substantial equivalence. | Demonstrated substantially equivalent performance when compared with the CLSI reference method. |
| Prediction of mecA-mediated resistance | Designed to predict this resistance. | Successfully demonstrated substantial equivalence in predicting mecA-mediated resistance. |
2. Sample Size Used for the Test Set and Data Provenance
The study utilized an external evaluation with:
- Fresh and stock clinical isolates
- Stock challenge strains
The specific sample size (number of isolates/strains) used for the test set is not explicitly stated in the provided document.
The data provenance indicates the use of clinical isolates, suggesting a representation of real-world scenarios. The document does not specify the country of origin for the data or whether the study was purely retrospective or prospective for the "external evaluation" portion, though "fresh...clinical isolates" implies a prospective component.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
The document does not provide information regarding the number of experts used to establish the ground truth for the test set or their qualifications.
4. Adjudication Method for the Test Set
The document does not describe any adjudication method used for the test set.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
A Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not performed as this device is an automated, in vitro diagnostic system, not a device requiring human interpretation of results. The comparison was against a widely accepted reference method (CLSI disk diffusion test), not human readers.
6. If a Standalone Performance (Algorithm Only Without Human-in-the-Loop Performance) Was Done
Yes, a standalone performance study was done. The VITEK® 2 Gram Positive Cefoxitin Screen is an automated system (VITEK 2 and VITEK 2 Compact Systems). The device itself generates a "positive or negative test result" at the completion of the incubation cycle. The study compared the performance of this automated system directly against the CLSI reference method without human interpretation of the device's test outcome.
7. The Type of Ground Truth Used
The ground truth used was the CLSI disk diffusion test, which is described as the "CLSI reference method" for predicting mecA-mediated resistance in staphylococci.
8. The Sample Size for the Training Set
The document does not provide information regarding the sample size for the training set. The descriptions focus on the external evaluation data used for performance validation.
9. How the Ground Truth for the Training Set Was Established
The document does not provide information on how the ground truth for the training set was established, as details about a distinct training set are not included. The focus is on the comparison of the device's performance against the CLSI reference method for validation.
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”