(56 days)
VITEK® 2 Gram Positive Linezolid is designed for antimicrobial susceptibility testing of Enterococcus faecalis, E. faecium, Staphylococcus aureus, S. epidermidis, S. haemolyticus and Streptococcus agalactiae. It is intended for use with the VITEK® 2 System as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents.
The VITEK 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) my 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 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 antibiotic contained on the card.
The VITEK 2 Gram Positive Linezolid device's acceptance criterion for performance is defined as 98.7% overall Essential Agreement when compared to the NCCLS microbroth dilution reference method.
The study proving the device meets this criterion is an external evaluation conducted with fresh and stock clinical isolates and stock challenge strains.
Here's the detailed information requested:
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance |
|---|---|
| Overall Essential Agreement ≥ 98.7% (with NCCLS microbroth dilution reference method) | 98.7% Overall Essential Agreement |
2. Sample size used for the test set and the data provenance
- Sample Size for Test Set: The document states that an "external evaluation was conducted with fresh and stock clinical isolates and stock challenge strains." However, the exact number of isolates or strains used in this test set is not specified within the provided text.
- Data Provenance: The data is described as from "fresh and stock clinical isolates and stock challenge strains," indicating a prospective and retrospective mix for the clinical isolates, and prospective for stock challenge strains. The country of origin is not specified.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
- The document does not specify the number of experts or their qualifications. The ground truth method used is the NCCLS microbroth dilution reference method, which is a standardized laboratory procedure, not typically relying on expert interpretation in the same way, for example, a medical imaging diagnosis would.
4. Adjudication method for the test set
- None specified. The ground truth is established by the NCCLS microbroth dilution reference method, which is a standardized laboratory method, not typically requiring an adjudication process for its results.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance
- No. This device is an automated antimicrobial susceptibility testing system, not an AI-assisted diagnostic tool that involves human readers interpreting results in the way an MRMC study would evaluate. Therefore, this type of study was not performed, and there is no mention of improvement in human reader performance with AI assistance.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
- Yes. The VITEK 2 system is a "Fully Automated Short-Term Incubation Cycle Antimicrobial Susceptibility Device." The performance evaluation compares the device's results directly to a reference method, which inherently describes its standalone, algorithm-only performance. The "human-in-the-loop" would be the initial preparation of the isolate and loading the card, but the interpretation and MIC determination are automated by the device.
7. The type of ground truth used
- The ground truth used is the NCCLS microbroth dilution reference method. This is a laboratory-based, standardized methodology for determining minimum inhibitory concentrations (MICs) of antimicrobial agents. It is considered the gold standard for antimicrobial susceptibility testing.
8. The sample size for the training set
- The document does not explicitly state a sample size for a training set. The described study is an "external evaluation" for performance confirmation. For a device incorporating a proprietary algorithm, training data would typically be used during development, but this information is not provided in the 510(k) summary.
9. How the ground truth for the training set was established
- As the training set sample size is not specified, the method for establishing its ground truth is also not described in the provided text. If a training set were used, it would likely also rely on the NCCLS microbroth dilution reference method or similar standardized laboratory methods to establish ground truth for MIC values.
§ 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.”