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VITEK 2 Gram Positive Doxycycline 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 Gram Positive Doxycycline is a qualitative test. Doxycycline has been shown to be active against the microorganisms listed below according to the FDA label for the antimicrobial.

Active in vitro and in clinical infections: Staphylococcus aureus

The VITEK 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK 2 and VITEK 2 Compact Systems for the automated quantitative or qualitative susceptibility testing of isolated colonies for the most clinically significant aerobic gramnegative bacilli, Staphylococcus sp., Enterococcus spp., Streptococcus agalactiae, and S. pneumoniae.

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 - 0 .50% 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 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 antibiotic contained on the card.

Here's an analysis of the provided text, outlining the acceptance criteria and study details for the VITEK® 2 Gram Positive Doxycycline device:

Acceptance Criteria and Device Performance Study for VITEK® 2 Gram Positive Doxycycline

1. Table of Acceptance Criteria and Reported Device Performance

The provided document refers to the acceptance criteria outlined in the "FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA, Issued March 5, 2007." While the specific numerical thresholds for this guidance document are not explicitly stated in the provided text, the device's performance is reported against these implied criteria.

Note: The exact numerical thresholds for "acceptable" are not provided in the submitted document, but the device states it demonstrated substantially equivalent performance and acceptable performance as defined by the guidance document.

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

• Sample Size for Test Set: Not explicitly stated as a single number. The study involved an "external evaluation using the VITEK 2 System conducted with fresh clinical isolates, challenge, quality control and reproducibility strains" and an "external evaluation using the VITEK 2 Compact instrument conducted with challenge, quality control and reproducibility strains."
• Data Provenance: The text indicates "fresh clinical isolates" were used. While the country of origin is not explicitly mentioned, bioMérieux, Inc. is based in Hazelwood, MO, USA, suggesting the data is likely from the United States. The evaluations were "external," indicating they were performed outside of the manufacturer's primary internal testing. The study design is prospective in nature, as it involved conducting evaluations with specific protocols.

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

The text does not specify the number of experts used or their qualifications. The ground truth was established by the "CLSI broth microdilution reference method." This method is a standardized laboratory procedure, and while it requires trained personnel to perform, it is not established through expert consensus in the same way, for example, a radiologic diagnosis might be.

4. Adjudication Method for the Test Set

The concept of an "adjudication method" (like 2+1 or 3+1) is not applicable here, as the comparison is against a reference laboratory method (CLSI broth microdilution) rather than expert interpretation or consensus where discrepancies would need to be resolved. Performance metrics (Essential Agreement, Category Agreement) are calculated directly by comparing the device's results to the reference method's results.

5. 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

No, a Multi Reader Multi Case (MRMC) comparative effectiveness study was not done. This device is an automated antimicrobial susceptibility testing (AST) system, not an AI-assisted diagnostic tool for human readers. Its purpose is to automate and provide faster results for antimicrobial susceptibility, replacing or supplementing traditional manual laboratory methods, not to assist human interpretation of complex images or data.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, a standalone performance study was done. The VITEK® 2 system is a "Fully Automated Short-Term Incubation Cycle Antimicrobial Susceptibility Device." The evaluations compare the device's performance directly against the CLSI reference method. While a human initiates the test and interprets the final report, the core susceptibility determination is performed by the automated system (algorithm).

7. The Type of Ground Truth Used

The type of ground truth used was a reference laboratory method: the CLSI broth microdilution reference method. This is considered the gold standard for determining minimum inhibitory concentration (MIC) and susceptibility categories for antimicrobials.

8. The Sample Size for the Training Set

The text does not explicitly mention a "training set" or its sample size. For an automated AST system like VITEK 2, the "training" (or development) of the algorithm to interpret growth patterns and determine MICs would likely occur during its initial design and validation phases. The document focuses on the performance evaluation (test set) of the finalized device.

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

As with the training set itself, the method for establishing ground truth for any internal development or "training" phases is not described in the provided document. However, it is highly probable that the CLSI broth microdilution reference method would have been extensively used during the development and calibration of the VITEK 2 system's algorithms to ensure accurate MIC determination based on microbial growth patterns.

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