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510(k) Data Aggregation
(61 days)
VITEK® 2 Streptococcus Levofloxacin is designed for antimicrobial susceptibility testing of Streptococcus species. VITEK 2 Streptococcus Levofloxacin 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. Levofloxacin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.
Active in vitro and in clinical infections Streptococcus pneumoniae (including multi-drug resistant strains [MDRSP]) Streptococcus pyogenes
Active in vitro but clinical significance unknown β-hemolytic Streptococcus (Group C/F) B-hemolytic Streptococcus (Group G) Streptococcus agalactiae Streptococcus milleri Viridans group Streptococci
The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 System 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 spp. and clinically significant yeast.
The VITEK 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique for determining the minimum inhibitory concentration (MIC). 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 cvcle, 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 Streptococcus Levofloxacin has the following concentrations in the card: 1. 2. 4 and 16 ug/mL (equivalent standard method concentration by efficacy in ug/mL). The MIC result range for the VITEK 2 card is ≤ 0.25 -> 16ug/mL.
This document describes the VITEK® 2 Streptococcus Levofloxacin system, a device for antimicrobial susceptibility testing of Streptococcus species, and its performance evaluation for FDA 510(k) clearance.
1. Acceptance Criteria and Reported Device Performance
The acceptance criteria for the VITEK® 2 Streptococcus Levofloxacin system are not explicitly stated as quantitative thresholds in the provided text. However, standard AST guidance documents and FDA interpretive criteria are referenced, implying the following would be the acceptance criteria. The reported device performance is derived from the "Method comparison with predicate device" section.
| Metric | Acceptance Criteria (Implied from Guidance) | Reported Device Performance (Clinical + Challenge combined) |
|---|---|---|
| Essential Agreement (EA) | High percentage (typically >90-95%) | 99.0% |
| Category Agreement (CA) | High percentage (typically >90-95%) | 97.9% |
| Major Discrepancies (maj) | Low (typically <3%) | 0 (0%) |
| Very Major Discrepancies (vmj) | Low (typically <3%) | 0 (0%) |
| Minor Discrepancies (min) | Low (typically <7%) | 32 (2.1%) |
Note on Minor Discrepancies: All 32 minor errors observed involved a shift from "Susceptible" by the reference method to "Intermediate" by the VITEK system. This indicates a slightly conservative bias in the VITEK system's interpretation for these cases.
2. Sample Size and Data Provenance
- Test Set Sample Size:
- Clinical Isolates: 1338
- Challenge Isolates: 207
- Total Combined Test Set: 1545 isolates
- Data Provenance: The isolates were sourced from clinical specimens, with the majority being recently isolated. These studies were conducted at four external clinical sites. The country of origin of the data is not explicitly stated, but clinical studies for FDA clearance are typically conducted within the US or its territories, or in regions where clinical practices align with US standards. The study appears to be retrospective for the clinical isolates (recently isolated from clinical specimens) and prospective for the challenge isolates (a specifically evaluated set).
3. Number and Qualifications of Experts for Ground Truth
The document does not specify the number of experts used or their specific qualifications (e.g., radiologist with 10 years of experience) for establishing ground truth. The ground truth was established by a CLSI broth microdilution reference method, which is a standardized laboratory procedure, not typically relying on expert interpretation in the same way as, for example, image-based diagnostics.
4. Adjudication Method
The concept of an "adjudication method" (like 2+1 or 3+1) is typically applied in studies where multiple human readers or experts independently assess cases, and their discrepancies are resolved through a structured process. In this context of antimicrobial susceptibility testing, the CLSI broth microdilution reference method served as the gold standard, removing the need for a human-based adjudication process for the test set interpretation. Discrepancies between the device and the reference method were identified and categorized as major, very major, or minor.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC comparative effectiveness study was done. This type of study investigates how human readers' performance changes with AI assistance. The VITEK 2 system is an automated device designed to replace or assist traditional AST methods, rather than directly assisting human readers in interpreting results from other sources.
6. Standalone Performance Study
Yes, a standalone performance study was done. The entire performance evaluation described in section M (Performance Characteristics) and section 2.a (Method comparison with predicate device) evaluates the algorithm's performance (the VITEK 2 system) directly against a gold standard (CLSI broth microdilution reference method), without human intervention in the interpretation of the VITEK 2 results.
7. Type of Ground Truth Used
The type of ground truth used was the CLSI broth microdilution reference method. This is a well-established and standardized laboratory method for determining minimum inhibitory concentrations (MICs) of antimicrobials. It serves as the gold standard for AST.
8. Sample Size for the Training Set
The document does not explicitly state a separate "training set" sample size. For an AST system like VITEK 2, the development typically involves extensive internal testing and refinement using a large, diverse collection of isolates before formal comparative studies are conducted for regulatory submission. The provided sample sizes (1338 clinical and 207 challenge isolates) pertain to the test set used for the formal performance evaluation.
9. How Ground Truth for the Training Set was Established
Since a separate "training set" is not explicitly mentioned as distinct from the test set in the context of this submission, the method for establishing ground truth for any internal development/training would likely also have been the CLSI broth microdilution reference method or a similar validated reference method, given its role as the industry standard. However, the specific details for any such internal "training set" are not provided in this document.
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