(49 days)
VITEK® 2 Gram Negative Levofloxacin is designed for antimicrobial susceptibility testing of Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Serratia marcescens, Acinetobacter baumannii, Acinetobacter Iwoffi, Citrobacter koseri, Citrobacter freundii, Enterobacter aerogenes, Enterobacter sakazakii, Klebsiella oxytoca, Morganella morganii, Pantoea agglomerans, Proteus vulgaris, Providencia rettgeri, Providencia stuartii, Pseudomonas fluorescens. VITEK 2 Gram Negative Levofloxacin is a quantitative test. 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 antimicrobial presented in VITEK 2 AST Cards is in concentrations equivalent by efficacy to standard method concentrations in mog/m!. 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 System 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 that contains the MC value along with the interpretive category result for each antibiotic contained on the card.
Here's a breakdown of the acceptance criteria and the study details for the VITEK® 2 Gram Negative Levofloxacin device, based on the provided document:
Acceptance Criteria and Device Performance
1. Table of Acceptance Criteria and Reported Device Performance
| Metric | Acceptance Criteria (Defined by FDA Guidance Document) | Reported Device Performance (VITEK® 2 Gram Negative Levofloxacin) |
|---|---|---|
| Overall Category Agreement | "Substantially equivalent performance when compared with the CLSI broth microdilution reference method, as defined in the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA, Issued Feb. 5, 2003." | 95.8% |
| Reproducibility | Acceptable results (implied by the FDA guidance) | Acceptable results |
| Quality Control | Acceptable results (implied by the FDA guidance) | Acceptable results |
Note: The specific numerical thresholds for "acceptable results" for reproducibility and quality control are not provided in this summary but are implicit in the cited FDA guidance document. The overall category agreement of 95.8% is explicitly stated as acceptable performance.
Study Details
2. Sample size used for the test set and the data provenance
- Test Set Sample Size: Not explicitly stated as a single number. The study utilized "fresh and stock clinical isolates and stock challenge strains."
- Data Provenance: Not explicitly stated (e.g., specific countries). The term "external evaluation" suggests data collected outside of the device manufacturer's core development environment, likely from multiple clinical sites. The data is retrospective and/or prospective, as it includes "fresh and stock clinical isolates" (fresh would be prospective, stock would be retrospective).
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 document. The ground truth was established by the CLSI broth microdilution reference method, which is a standardized laboratory procedure, not typically an assessment by human experts in the sense of clinical interpretation.
4. Adjudication method for the test set
- Not applicable / None. The ground truth was established by the CLSI broth microdilution reference method, which is a direct measurement, not an adjudicated human interpretation.
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
- This is not applicable. The VITEK® 2 system is an automated device for antimicrobial susceptibility testing. It's not an AI system designed to assist human readers in interpreting images or clinical data. Its "performance" is compared to a reference method, not to human interpretation.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
- Yes. The study evaluated the VITEK® 2 Gram Negative Levofloxacin system (which includes the instrument and the AST cards) against the CLSI broth microdilution reference method. This is a standalone performance assessment of the automated system. The VITEK 2 automatically fills, seals, incubates, and reads the cards to generate results.
7. The type of ground truth used
- CLSI broth microdilution reference method. This is a recognized standard laboratory method for determining minimum inhibitory concentrations (MICs) of antimicrobial agents.
8. The sample size for the training set
- Not explicitly stated. The document describes a verification study (external evaluation) and doesn't explicitly detail a separate "training set" within the context of model development, which is typical for machine learning models. For a device like VITEK 2, the "training" data would likely refer to the extensive development and internal validation data used to optimize the algorithms for growth detection and MIC determination, which is not detailed here.
9. How the ground truth for the training set was established
- Not explicitly stated. Similar to point 8, the document doesn't detail how ground truth was established for an explicit "training set." However, it's reasonable to infer that during internal development and optimization, the CLSI broth microdilution reference method (or similar gold standard methods) would have been used to establish ground truth for any data used to refine the device's algorithms.
§ 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.”