(55 days)
VITEK® 2 AST-GP Clindamycin is designed for antimicrobial susceptibility testing of Staphylococcus aureus and Staphylococcus epidermidis. VITEK 2 AST-GP Clindamycin is a quantitative test 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. Clindamycin has been shown to be active against most strains of the microorganism listed below, according to the FDA label for this antimicrobial.
Active in vitro and in clinical infections Staphylococcus aureus (methicillin-susceptible strains) and Staphylococcus epidermidis (methicillin-susceptible strains)
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 gram-negative 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 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.
The VITEK® 2 AST - Gram Positive Clindamycin device is designed for antimicrobial susceptibility testing of Staphylococcus aureus and Staphylococcus epidermidis. The study aimed to demonstrate its substantial equivalence to the CLSI broth microdilution reference method.
1. Table of Acceptance Criteria and Reported Device Performance
| Performance Metric | Acceptance Criteria (from Class II Special Controls Guidance) | Reported Device Performance |
|---|---|---|
| Overall Category Agreement | Not explicitly stated in the provided text but implied by "acceptable performance" and comparison to CLSI guidance. Typically, for AST devices, this is >= 90-95% for essential agreement and category agreement. | 99.4% Overall Category Agreement |
| Reproducibility | Acceptable results (implied by CLSI guidance) | Acceptable results |
| Quality Control | Acceptable results (implied by CLSI guidance) | Acceptable results |
2. Sample size used for the test set and the data provenance
The document mentions an "external evaluation" conducted with:
- Fresh and stock clinical isolates: The exact number is not specified.
- Stock challenge strains: The exact number is not specified.
The provenance of the data (e.g., country of origin) is not explicitly stated, but it is an "external evaluation," suggesting it was not solely internal data from bioMérieux. It also doesn't explicitly state if the data was retrospective or prospective, though clinical isolates generally imply prospective collection or recent isolates.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
This information is not provided in the given text. The ground truth method is the CLSI broth microdilution reference method, which is a standardized laboratory procedure, not typically established by human experts in the same way imaging or pathology ground truth might be.
4. Adjudication method for the test set
This information is not applicable and therefore not provided. The ground truth is established by a standardized laboratory reference method (CLSI broth microdilution), not through expert consensus requiring adjudication.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This type of study is typically relevant for interpretative diagnostic devices where human reading is involved, such as medical imaging. For an antimicrobial susceptibility test system, the comparison is between the automated device and a standardized reference method.
6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done
Yes, the study describes a standalone performance evaluation. The VITEK® 2 AST system, in both VITEK 2 and VITEK 2 Compact platforms, generates results (MIC value and interpretive category) autonomously. Its performance was compared directly against the CLSI broth microdilution reference method without human intervention in the result determination phase of the device itself.
7. The type of ground truth used
The type of ground truth used was the CLSI broth microdilution reference method. This is a well-established, standardized laboratory methodology for determining antimicrobial susceptibility, considered the gold standard for MIC determination.
8. The sample size for the training set
The sample size for the training set is not specified. The document describes an "external evaluation" which sounds more like a validation or test set rather than a training set. For an AST system, the device's algorithms or measurement principles are developed based on understanding microbial growth kinetics and established breakpoints, rather than explicitly "training" on a large dataset of results in the way machine learning algorithms are. The provided text focuses on the performance comparison of the final device.
9. How the ground truth for the training set was established
As mentioned above, specific information about a "training set" and its ground truth establishment is not provided in the context of typical machine learning training. The VITEK® 2 system's underlying methodology likely relies on established microbiological principles and standardized breakpoints. If internal development involved optimization, the ground truth would similarly be established by reference methods like CLSI broth microdilution for those internal studies.
§ 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.”