Search Results

VITEK® 2 AST-Gram Positive Telavancin is designed for antimicrobial susceptibility testing of Gram positive microorganisms 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 AST-Gram Positive Telavancin is a quantitative test. Telavancin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active both in vitro and in clinical infections Staphylococcus aureus (including methicillin-resistant isolates) Enterococcus faecalis (vancomycin-susceptible isolates only)

The VITEK® 2 Gram-positive Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of Staphylococcus spp., Enterococcus spp., and S. agalactiae to antimicrobial agents when used as instructed.

The principle of the VITEK®2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh(1) and Gerlach(0). The VITEK @ 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique(3).

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 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.

Here's an analysis of the provided text regarding the VITEK 2 AST-GP Telavancin device, broken down by your requested categories:

1. Table of Acceptance Criteria and Reported Device Performance

Notes on Acceptance Criteria:

• The document explicitly states the device demonstrated "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 August 28, 2009)." This guidance document outlines the typical performance metrics and acceptable thresholds for AST devices. While the exact numerical criteria are not given in this summary, they are implicitly met if the FDA clears the device. Common thresholds for these metrics are generally around >90% for EA and CA, and low rates (e.g., <3%) for VME and ME.
• For Enterococcus faecalis, the document notes that five major errors were within essential agreement, and due to the lack of an intermediate breakpoint, these were considered acceptable. This adjusted the major error rate for E. faecalis to 5.7%, with a requirement for retesting non-susceptible strains.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size:
  • Enterococcus faecalis: 368 isolates
  • Staphylococcus aureus: 520 isolates
  • The total number of unique isolates is not explicitly stated if there are overlaps (e.g., some isolates tested for both).
• Data Provenance: "An external evaluation was conducted with contemporary and stock clinical isolates, as well as a set of challenge strains." This suggests a mix of retrospective (stock and some clinical) and prospective (contemporary clinical) data. The country of origin is not specified.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of those Experts

• This information is not provided in the summary.
• For Antimicrobial Susceptibility Testing (AST) devices, the ground truth is typically established by an independent, validated reference method performed by trained microbiologists. The concept of "experts" in the context of expert consensus or adjudication (as in medical imaging) is generally not directly applicable to the establishment of ground truth for AST, where a standardized laboratory method (CLSI broth microdilution) serves as the "gold standard."

4. Adjudication Method for the Test Set

• This information is not applicable in the traditional sense of human adjudication for AST devices. The "adjudication" is inherent in the comparison of the device's Minimum Inhibitory Concentration (MIC) and interpretive category (Susceptible, Intermediate, Resistant) with the results from the CLSI broth microdilution reference method. Discrepancies are categorized as Essential Agreement, Category Agreement, VME, ME, or mE. The document mentions an adjustment for E. faecalis major errors due to breakpoint interpretation, which is an analytical decision, not a human reader adjudication.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done and the effect size of how much human readers improve with AI vs without AI assistance

• This is not applicable to this device. The VITEK 2 AST system is an automated in vitro diagnostic device for antimicrobial susceptibility testing, not an AI-powered diagnostic imaging tool that assists human readers.

6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) was done

• Yes, a standalone study was done. The VITEK® 2 AST-GP Telavancin is an automated system. Its performance was directly compared against the CLSI broth microdilution reference method without human intervention in the interpretation of the VITEK 2 results during the performance study. This comparison establishes the "algorithm only" performance.

7. The Type of Ground Truth Used

• CLSI broth microdilution reference method incubated at 16-20 hours for Staphylococci and Enterococci, and 20-24 hours for Streptococci. This is a laboratory-based reference standard widely accepted as the gold standard for antimicrobial susceptibility testing.

8. The Sample Size for the Training Set

• The document does not explicitly state a separate "training set" sample size or method. For AST systems like VITEK 2, the "training" (i.e., development and optimization of the growth pattern analysis algorithm) would have occurred during the initial development of the VITEK 2 platform itself and may not be a distinct "training set" for each new antimicrobial/organism combination. The external evaluation described serves as the validation/test set.

9. How the Ground Truth for the Training Set was Established

• As a training set is not explicitly mentioned for this specific antimicrobial, the method for establishing ground truth for any underlying algorithm development is not detailed in this summary. However, for AST devices, any algorithm development would typically rely on extensive data where the MICs and interpretive categories were determined by the same CLSI broth microdilution reference method.

Ask a specific question about this device