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VITEK® 2 AST- Gram Positive Clindamycin Resistance is designed for antimicrobial susceptibility testing of Staphylococcus aureus, Staphylococcus lugdunensis, and Coagulase Negative Staphylococcus spp. VITEK® 2 AST- Gram Positive Inducible Clindamycin Resistance is a qualitative 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 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 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.

The provided text describes the acceptance criteria and the study that proves the device meets the acceptance criteria for the VITEK® 2 AST-Gram Positive Inducible Clindamycin Resistance system.

Here's a breakdown of the requested information:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for antimicrobial susceptibility test (AST) systems are typically defined by specific percentages for Essential Agreement (%EA), Category Agreement (%CA), Very Major Errors (VME), Major Errors (ME), and Minor Errors (mE). While the table in the document only explicitly lists values for %CA, VME, ME, and mE under "Overall Performance" (implying these are the performance metrics assessed against the reference method), it also mentions adhering to 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 would contain the specific numerical acceptance criteria.

Based on the provided text, here's the reported performance:

Note: The table in the document is missing a reported value for 'mE' under the "Overall Performance" heading and the %EA column has "N/A" for reported performance. However, the text clearly states, "The VITEK® 2 AST-GP Inducible Clindamycin Resistance demonstrated acceptable performance as presented in Table 1 below." This implies that the metrics presented or implied within the table (even if not explicitly filled in) met the established acceptance criteria. For a comprehensive understanding of the numerical acceptance criteria, the specific FDA guidance document cited would need to be consulted.

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

• Test Set Sample Size: Not explicitly stated as a numerical count of isolates in the provided text. The text mentions "an external evaluation was conducted with fresh and stock clinical isolates, as well as a set of challenge strains." This suggests a diverse collection but no specific number.
• Data Provenance:
  • Country of Origin: Not specified in the provided text.
  • Retrospective or Prospective: Not explicitly stated. However, "fresh and stock clinical isolates" indicates a mix of prospectively collected (fresh) and retrospectively collected (stock) isolates. "Challenge strains" are typically laboratory-maintained strains and are neither purely retrospective nor prospective in the clinical sense.

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

• Number of Experts: Not applicable. The ground truth for this device is not established by human experts in a subjective reading task like image interpretation. Instead, it is established by a reference laboratory method.
• Qualifications of Experts: Not applicable, as the ground truth is derived from a standardized laboratory method.

4. Adjudication Method for the Test Set

• Adjudication Method: Not applicable. The ground truth is established by a defined laboratory methodology (CLSI broth microdilution reference method), not by expert consensus requiring adjudication.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• MRMC Study: No, an MRMC comparative effectiveness study was not done. This type of study is relevant for diagnostic imaging AI algorithms where the AI assists human readers. This device is an automated antimicrobial susceptibility testing system, and its performance is compared against a gold standard laboratory method, not typically against human interpretation of the AST results.
• Effect Size: Not applicable.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance)

• Standalone Performance: Yes, the study evaluated the standalone performance of the VITEK® 2 AST-GP Inducible Clindamycin Resistance system. The comparison "with the CLSI broth microdilution reference method" directly assesses the ability of the VITEK® 2 system to accurately determine susceptibility, independent of human interpretation or assistance beyond the initial sample preparation and loading.

7. Type of Ground Truth Used

• Type of Ground Truth: The ground truth used was the CLSI broth microdilution reference method, incubated at 16-20 hours. This is a recognized laboratory standard for determining antimicrobial susceptibility.

8. Sample Size for the Training Set

• Training Set Sample Size: Not explicitly stated. The document describes the external evaluation (test set) but does not provide details on the training set used for the development or initial validation of the VITEK® 2 system's internal algorithms. For a commercially available AST system, the "training" (or more accurately, the development and internal validation) would involve a large, diverse set of isolates representative of the target organisms and resistance patterns.

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

• Ground Truth for Training Set: While not explicitly detailed for a specific training set, it can be inferred that any isolates used during the development and internal validation of the VITEK® 2 system's algorithms would have had their ground truth established using standard reference methods, similar to the test set (e.g., CLSI broth microdilution or agar dilution methods). The principle is consistent: compare the device's output against an accepted, accurate laboratory method.

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