(37 days)
VITEK 2® Gram Positive Moxifloxacin is designed for antimicrobial susceptibility testing of Staphylococcus aureus (methicillin-susceptible strains only). 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) 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.
Here's a summary of the acceptance criteria and study details for the VITEK® 2 Gram Positive Moxifloxacin, based on the provided text:
1. Acceptance Criteria and Reported Device Performance:
| Acceptance Criteria (from FDA Draft Guidance) | Reported Device Performance (VITEK® 2 Gram Positive Moxifloxacin) |
|---|---|
| Sufficient Essential Agreement with reference method | 99.2% overall Essential Agreement |
2. Sample Size Used for the Test Set and Data Provenance:
The document mentions "fresh and stock clinical isolates and stock challenge strains". It does not explicitly state the exact sample size for the test set.
- Data Provenance: Not explicitly stated, though the mention of "external evaluation" suggests multiple sites, potentially within the USA, given the FDA submission. The letter from the FDA does state "Over the country USA" likely referring to the manufacturer's location, rather than data provenance.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts:
The ground truth was established using the NCCLS reference agar dilution method. This is a standardized laboratory method for determining antimicrobial susceptibility, not directly an expert consensus in the typical sense (e.g., a panel of radiologists). While laboratories performing this method require trained personnel, the document does not specify the number of individuals or their specific qualifications beyond adherence to the NCCLS standard.
4. Adjudication Method for the Test Set:
Not applicable. The comparison was made against a standardized laboratory reference method (NCCLS agar dilution), not human expert interpretations requiring adjudication.
5. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study:
No, an MRMC study was not performed. This device is an automated antimicrobial susceptibility testing system, not an imaging or diagnostic AI requiring human-in-the-loop performance evaluation.
6. Standalone Performance:
Yes, a standalone performance study was done. The VITEK® 2 Gram Positive Moxifloxacin was compared directly against the NCCLS reference agar dilution method to determine its "Essential Agreement."
7. Type of Ground Truth Used:
The ground truth used was the NCCLS reference agar dilution method. This is a validated laboratory method considered the gold standard for determining minimum inhibitory concentration (MIC) and susceptibility in microbiology.
8. Sample Size for the Training Set:
The document does not explicitly mention a separate "training set" or its size. The described validation study details an "external evaluation" that tested the VITEK® 2 system. For such automated systems, "training" might refer to the development and calibration of the algorithm itself using internal data, which would likely have preceded this external validation study.
9. How the Ground Truth for the Training Set Was Established:
As no explicit training set is detailed, the method for establishing its ground truth is not provided. If the device's algorithms were developed internally, it's highly probable they were trained against similar reference methods (like agar dilution) to establish accurate MIC readings and interpretive categories.
§ 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.”