Search Results

VRESelect ™ is a selective and differential chromogenic medium, containing 8 µg/mL of vancomycin, for the qualitative detection of gastrointestinal colonization of vancomycin-resistant Enterococcus faecium (VREfm) and vancomycin-resistant Enterococcus faecalis (VREfs) and to aid in the prevention and control of vancomycin-resistant Enterococcus (VRE) in healthcare settings. The test is performed on rectal swabs or fecal specimens from patients to be screened for VRE colonization. VRESelect ™ is not intended to diagnose VRE infection nor to guide or monitor treatment of infection. Results can be interpreted after 24 to 28 hours incubation. Subculture to non-selective media (e.g., trypticase soy agar with 5% sheep blood) is needed for susceptibility testing and epidemiological typing.

VRESelect ™ is a selective medium for the detection of vancomycin-resistant Enterococcus (VRE). The selectivity of this medium is based on the presence of an antifungal/antibiotic mixture that inhibits the growth of most yeast, Gram negative and Gram positive bacteria, with the exception of vancomycin-resistant Enterococci (VRE).

Detection is based on the cleavage of chromogenic substrates by specific enzymes of Enterococcus faecium which produces pink colonies and Enterococcus faecalis which produces blue colonies.

Enterococcus gallinarum and Enterococcus casseliflavus are intrinsically resistant to vancomycin and may grow on the VRESelect™ medium as colorless or white colonies because they do not metabolize the chromogenic substrates. Vancomycin susceptible enterococci are inhibited.

After 24 to 28 hours incubation pink colonies can be reported as VREfm. Blue colonies should be confirmed by a catalase test and susceptibility (refer to limitation 9 in package insert).

K122187: VRESelect™ Media Acceptance Criteria and Performance Study

The VRESelect™ Media is a selective and differential chromogenic medium intended for the qualitative detection of gastrointestinal colonization of vancomycin-resistant Enterococcus faecium (VREfm) and Enterococcus faecalis (VREfs).

1. Acceptance Criteria and Reported Device Performance

The acceptance criteria for VRESelect™ Media are not explicitly stated as numerical thresholds in this document. However, performance is assessed through comparison with a predicate device (BEAV + Confirmation) and established laboratory methods (Biochemical identification (Vitek) and Vancomycin minimal inhibitory concentration (MIC) by E-Test). The implicit acceptance criteria appear to be high levels of positive and negative agreement with these reference methods.

The conclusion states that "The VRESelect™ showed high diagnostic sensitivity and accuracy in this study," indicating that the reported performance met the sponsor's internal acceptance criteria.

2. Sample Size and Data Provenance for the Test Set

• Sample Size: 946 stool samples were used for the method comparison study.
• Data Provenance: The document does not explicitly state the country of origin for the samples. It also doesn't specify if the samples were retrospective or prospective, though the nature of a method comparison study often implies prospectively collected samples or a mixed approach.

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

The document does not specify the number of individual experts involved in establishing the ground truth for the test set. However, it indicates these processes:

• For the Method Comparison Study (vs. BEAV + Confirmation): It states "confirmatory testing (Gram stain, catalase, PYR, Vitek 2 identification and vancomycin (MIC E-Test))." This implies established laboratory protocols and potentially certified laboratory personnel rather than individual "experts" in the sense of clinical specialists.
• For Biochemical identification (Vitek) and Vancomycin minimal inhibitory concentration (MIC) (E-Test): These are standard laboratory methods with established protocols.

No specific qualifications (e.g., "radiologist with 10 years of experience") are mentioned for these individuals, as the ground truth relies on recognized laboratory tests rather than expert interpretation of images or clinical findings.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method in the context of multiple human readers or interpretations. The ground truth for the test set was established through a combination of a predicate device (BEAV) and a series of confirmatory laboratory tests (Gram stain, catalase, PYR, Vitek 2 identification, and vancomycin (MIC E-Test)). These are objective laboratory procedures, which typically do not involve an "adjudication" process in the same way clinical interpretations might.

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

No, an MRMC comparative effectiveness study was not performed. The study evaluates the performance of the VRESelect™ medium itself against established laboratory methods, not how human readers improve with or without AI assistance. The device is a culture medium, not an AI or human-assisted diagnostic tool in the typical sense of an MRMC study.

6. Standalone Performance Study

Yes, a standalone performance study was done. The entire document describes the performance of the VRESelect™ media (the algorithm/device only, without human interpretation beyond reading the colonies) against established ground truth methods. The results are presented as agreement percentages.

7. Type of Ground Truth Used

The ground truth used was a combination of:

• Predicate Device Performance: The results from the current standard, "BEAV plus Confirmation."
• Laboratory Diagnostic Tests: This includes Gram stain, catalase, PYR, Vitek 2 identification, and vancomycin (MIC E-Test) for bacterial identification and resistance determination. This aligns with what can be considered definitive laboratory methods/gold standard diagnostic tests.

8. Sample Size for the Training Set

The document does not explicitly mention a separate "training set" or "training data" in the context of machine learning model development. This is because VRESelect™ is a chromogenic culture medium, not an AI/machine learning algorithm that requires training. Its performance is based on biochemical reactions and enzymatic activity, which are inherent properties of the medium. The studies described are validation or verification studies, not training for an adaptive algorithm.

However, if we interpret "training" in a broader sense of product development and optimization, the "limit of detection study" involving a panel of 18 vancomycin-resistant enterococci and the "challenge panel" of 56 well-characterized strains could be considered part of the development and refinement process, though not a "training set" for a learning algorithm.

9. How the Ground Truth for the Training Set (if applicable) was Established

As noted above, there is no explicit "training set" as understood in machine learning. For the studies that involved characterized strains (e.g., Limit of Detection, Challenge Panel), the ground truth for these strains would have been established through well-defined microbiological methods, including identification to species level and vancomycin susceptibility testing using standard laboratory techniques (e.g., AST methods like MIC E-Test or broth microdilution). The "ATCC reference strains" mentioned in the reproducibility study also serve as a form of "ground truth" with known characteristics.

Ask a specific question about this device

VRESelect ™ is a selective and differential chromogenic medium, containing 8 µg/mL of vancomycin, for the qualitative detection of gastrointestion of vancomycin-resistant Enterococcus faecium (VREfm) and vancomycin-resistant Enterococcus faecalis (VREfs) and to aid in the prevention and control of vancomycin-resistant Enterococcus (VRE) in healthcare settings. The test is performed on rectal swabs from patients to be screened for VRE colonization. VRESelect ™ is not intended to diagnose VRE infection nor to guide or monitor treatment of infection. Results can be interpreted after 24 to 28 hours incubation. Subculture to non-selective media (e.g., trypticase soy agar with 5% sheep blood) is need for susceptibility testing and epidemiological typing.

VRESelect ™ is a selective medium for the detection of vancomyoin-resistant Enterococcus (VRE). The selectivity of this medium is based on the presence of an antifungal/antibiotic mixture that inhibits the growth of most yeast, Gram negative and Gram positive bacteria, with the exception of vancomycin-resistant Enterococci (VRE).

Detection is based on the cleavage of chromogenic substrates by specific enzymes of Enterococcus facium which produces pink colonies and Enterococcus faecalis which produces blue colonies.

Enterococcus gallinarum and Enterocccus casseliflavus are intrinsically resistant to vancomycin and may grow on the VRESelect™ medium as colories or white colonies because they do not metabolize the chromogenic substrates. Vancomycin susceptible enterococci are inhibited.

After 24 to 28 hours incubation pink colonies can be reported as VRESm. Blue colonies should be confirmed by a catalase test and susceptibility testing (refer to limitation 8 in package insert).

The provided text describes the performance of VRESelect™ Culture Media, which is a selective and differential chromogenic medium for the detection of vancomycin-resistant Enterococcus (VRE).

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state "acceptance criteria" in a numerical target format (e.g., "sensitivity must be >90%"). However, the "Method Comparison" section and the subsequent tables present performance metrics (Positive Agreement and Negative Agreement) against established reference methods, which implicitly serve as the acceptance criteria for the device to be deemed "substantially equivalent."

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

• Sample Size:
  • Method Comparison (BEAV + Confirmation): 757 specimens.
  • Biochemical Identification (Vitek 2) & Vancomycin MIC: Based on the same 757 specimens, but stratified by VREfm (97 positive for VREfm, 660 negative) and VREfs (38 positive for VREfs, 719 negative) for Vitek 2, and VREfm (94 resistant, 637 susceptible) and VREfs (28 resistant, 637 susceptible) for Vancomycin MIC.
  • Cross-Reactivity: 119 microorganisms.
  • Recovery Study: Panel of eighteen vancomycin-resistant enterococci (8 VREfm and 10 VREfs).
  • Reproducibility: 6 ATCC reference strains.
  • Challenge Panel: 56 well-characterized strains.
  • Interfering Substances: Multiple substances tested, but specific strain counts not given for each.
• Data Provenance: The document does not specify the country of origin. It is a 510(k) submission to the FDA, implying studies conducted to US regulatory standards, but the physical location of the patient sample collection is not mentioned. The data appears to be prospective as it involves testing specimens with the VRESelect™ media and comparing them to reference methods.

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

The document does not explicitly mention "experts" in the context of establishing ground truth for the test set in the same way one might in imaging studies. Instead, the ground truth is established through standard microbiological laboratory procedures:

• "BEAV + Confirmation": The confirmation included "Gram stain, catalase, PYR, Vitek 2 identification and vancomycin (MIC E-Test)." These are objective laboratory tests. While trained microbiologists perform and interpret these tests, the ground truth is based on the results of these standardized methods rather than subjective expert consensus.
• "Biochemical identification (Vitek) vs. VRESelect™ results": Vitek 2 is an automated system for identification, which provides objective results.
• "Vancomycin minimal inhibitory concentration (MIC) demonstrated the following results": Vancomycin E-Test (MIC) provides an objective measure of antimicrobial resistance.

Therefore, the ground truth is established by a combination of conventional microbiological techniques and automated systems, interpreted by trained laboratory personnel, not by a panel of "experts" as in, for example, a radiology consensus read.

4. Adjudication Method for the Test Set

There's no mention of an "adjudication method" in the sense of multiple experts independently reviewing and then resolving discrepancies for the ground truth. The ground truth relies on objective laboratory tests ("BEAV + Confirmation," Vitek 2, Vancomycin MIC E-Test). Any discrepancies between VRESelect™ and these reference methods are presented as performance metrics (Positive/Negative Agreement) and sometimes further analyzed (e.g., false positives/negatives were sometimes confirmed by subculture to BAPs and further testing).

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

This document describes the performance of a culture medium, not an AI algorithm for diagnostic imaging. Therefore, an MRMC comparative effectiveness study involving human readers and AI assistance is not applicable and was not performed.

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

The VRESelect™ media is itself a diagnostic tool that produces a visible result (colony color). The "standalone" performance is effectively what is reported in the tables, where the media's results are compared directly to the reference methods (BEAV+Confirmation, Vitek 2, Vancomycin MIC). The interpretation of the visible colonies (pink/blue) is part of the "system" performance. There is no "algorithm only" in the sense of a software-based AI system operating independently of human observation of the culture medium.

7. The Type of Ground Truth Used

The ground truth used is a combination of:

• Expert Consensus (Implicit/Procedural): The "BEAV + Confirmation" method, which includes Gram stain, catalase, PYR, Vitek 2 identification, and vancomycin (MIC E-Test), represents a gold standard of laboratory procedures for identifying and confirming VRE, interpreted by trained microbiologists following established protocols.
• Pathology/Laboratory Results: Vitek 2 biochemical identification and vancomycin MIC E-Test are objective laboratory tests providing definitive identification and resistance profiles.

8. The Sample Size for the Training Set

The document does not explicitly differentiate between "training" and "test" sets in the context of an algorithm. This product is a culture medium, not a machine learning model that undergoes a training phase. The described studies represent validation studies for the performance of the medium.

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

As this is a culture medium, not an AI algorithm, there is no "training set" in the machine learning sense. The development of the medium would have involved internal R&D and testing, but the document focuses on the formal validation studies.

Ask a specific question about this device