(65 days)
VITEK® 2 Streptococcus Linezolid is designed for antimicrobial susceptibility testing of Streptococcus species and 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. VITEK® 2 Streptococcus Linezolid is a qualitative test. Linezolid 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 agalactiae Streptococcus pneumoniae (including multi-drug resistant isolates [MDRSP]) Streptococcus pyogenes
The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 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 spp. and clinically significant yeast.
The VITEK® 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) microdilution methodology. The isolate to be tested is diluted to a standardized concentration in 0.45 - 0.50% 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 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 MIC value along with the interpretive category result for each antimicrobial contained on the card.
Here's a summary of the acceptance criteria and study details for the VITEK® 2 AST-ST Linezolid device, based on the provided text:
Acceptance Criteria and Device Performance
| Acceptance Criteria | Reported Device Performance |
|---|---|
| Overall Essential Agreement | 99.8% |
| Overall Category Agreement | 99.8% |
Note: The specific numerical acceptance criteria (e.g., "should be ≥ 90%") are not explicitly stated in the provided text, only the achieved performance which was deemed "acceptable" and demonstrated "substantially equivalent performance" to the reference method.
Study Details
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Sample size used for the test set and the data provenance:
- Test Set Sample Size: Not explicitly stated as a number of isolates in the provided document. It refers to "fresh and stock clinical isolates" as well as "a set of challenge strains."
- Data Provenance: Not specified (e.g., country of origin). The study involved "an external evaluation." It included both prospective ("fresh clinical isolates") and retrospective ("stock clinical isolates") data, along with "challenge strains."
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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 document. The ground truth was established by a reference method rather than expert consensus on individual cases.
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Adjudication method for the test set:
- Not applicable. The ground truth was established by a single, standardized reference method (CLSI broth microdilution).
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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:
- Not applicable. This device is an automated antimicrobial susceptibility testing system, not an AI-assisted diagnostic tool that involves human readers interpreting results.
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If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Yes, this was a standalone study. The VITEK® 2 AST-ST Linezolid system, which is an automated device, was compared directly against the reference method. Its performance figures (Essential and Category Agreement) reflect the algorithm's performance without human intervention in the interpretation process of the device's output.
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The type of ground truth used:
- CLSI broth microdilution reference method: This is the gold standard method for determining minimum inhibitory concentrations (MICs) of antimicrobials, as defined by the Clinical and Laboratory Standards Institute (CLSI). The reference method was incubated for 24 hours.
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The sample size for the training set:
- The document does not specify a separate "training set" sample size. The VITEK® 2 system is a well-established platform, and the specific VITEK® 2 AST-ST Linezolid card for this antimicrobial likely builds upon existing algorithms. The reported study focuses on validation using the test set described.
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How the ground truth for the training set was established:
- Not explicitly stated for a "training set." If a training set was used in the development of the specific Linezolid card (which is likely, but not detailed here), the ground truth would also have been established using a recognized reference method like CLSI broth microdilution.
§ 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.”