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VITEK® 2 GN Imipenem is designed for antimicrobial susceptibility testing of Gram-negative bacilli. VITEK 2 GN Imipenem is a quantitative test intended for use with the VITEK 2 and VITEK 2 Compact Systems using VITEK 2 Systems 5.02 Software as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. Imipenem has been shown to be active both in vitro and in clinical infections against most strains of the following microorganisms according to the FDA label for the antimicrobial.

Active in vitro and in clinical infections:

Acinetobacter spp.
Citrobacter spp.
Enterobacter aerogenes
Escherichia coli
Klebsiella spp.
Morganella morganii
Proteus vulgaris
Providencia rettgeri
Pseudomonas aeruginosa
Serratia marcescens

Active in vitro but clinical significance unknown: Providencia stuartii

The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 System 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 agalactiae, S. pneumoniae and clinically significant yeast. The VITEK 2 Systems (PC) 5.02 Software is intended for use with VITEK 2 and VITEK 2 Compact Systems.

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 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 breakdown of the acceptance criteria and study information for the VITEK® 2 Gram Negative Imipenem & VITEK 2 Systems (PC) 5.02 Software, based on the provided text:

Acceptance Criteria and Device Performance

Note: The document states that the performance was "substantially equivalent" to 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 likely contains the specific numerical acceptance criteria that "acceptable performance" refers to, though they are not detailed in this excerpt.

Study Information

1. Sample size used for the test set and the data provenance:

   • Test Set Sample Size: Not explicitly stated as a total number. The study utilized "fresh clinical isolates and stock challenge strains."
   • Data Provenance: The study was an "external evaluation." No specific country of origin is mentioned, but "clinical isolates" imply real-world patient samples, and "stock challenge strains" are laboratory-maintained reference strains. The study type is prospective for the fresh clinical isolates and likely retrospective for the stock challenge strains.

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • Number of Experts: Not specified.
   • Qualifications of Experts: Not specified.

3. Adjudication method (e.g., 2+1, 3+1, none) for the test set:

   • Adjudication Method: Not specified. The comparison was made against the "CLSI broth microdilution reference method," which is a standardized laboratory procedure, not typically requiring expert adjudication in the same way imaging studies might.

4. 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:

   • MRMC Study: No, this was not a multi-reader multi-case comparative effectiveness study. This device is an automated antimicrobial susceptibility test system, not an AI-powered diagnostic tool requiring human interpretation. The comparison is between the automated system and a laboratory reference method.

5. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:

   • Standalone Performance: Yes, the described study evaluates the "VITEK 2 Gram Negative Imipenem" device's performance directly against the CLSI reference method. The VITEK 2 Systems (PC) 5.02 software is an integral part of the automated system, operating without direct human intervention in the interpretation of results during the test cycle.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

   • Type of Ground Truth: The ground truth was established by the CLSI broth microdilution reference method. This is a laboratory-standardized methodology for determining minimum inhibitory concentrations (MICs) of antimicrobials against bacteria.

7. The sample size for the training set:

   • Training Set Sample Size: Not specified. The document focuses on the evaluation of the device rather than its development or training.

8. How the ground truth for the training set was established:

   • Training Set Ground Truth: Not specified, as training set information is not provided.

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