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ImmunoCard C. difficile GDH is a rapid qualitative enzyme immunoassay screening test to detect Clostridium difficile antigen, glutamate dehydrogenase, in fecal specimens from persons suspected of having C. difficile infection (CDI). This test does not distinguish between toxigenic and non-toxigenic strains of C. difficile. Samples from patients that produce positive results with this test must be further tested with an assay designed to detect toxigenic C. difficile strains and assist with the diagnosis of CDI.

ImmunoCord C. difficile GDH is a rapid qualitative enzyme immunoassay screening test to detect Clostridium difficile antigen, glutamate dehydrogenase (GDH), in fecal specimens from persons suspected of having C. difficile infection. The assay consists of ImmunoCard C. difficile GDH Test Cards containing immobilized polyclonal anti-C. difficile GDH antibodies, ImmunoCard C. difficile GDH Positive Control, ImmunoCard C. difficile GDH Sample Diluent/Negative Control, ImmunoCard C. difficile GDH Enzyme Conjugate, ImmunoCard Wash Buffer I, and ImmunoCard Substrate I.

Here's an analysis of the ImmunoCard C. difficile GDH device based on the provided document, addressing the requested information:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for sensitivity and specificity are not explicitly stated as distinct "acceptance criteria" beyond the presented performance metrics. However, based on the desire to demonstrate substantial equivalence, the reported performance of the ImmunoCard C. difficile GDH is compared to bacterial culture as the reference.

(Note: The document implies these performance levels are the acceptance criteria for regulatory submission as they are the key clinical performance results presented for review.)

2. Sample size used for the test set and the data provenance

• Sample Size (Clinical Test Set): 975 qualified patient samples.
• Data Provenance:
  • Country of Origin: United States (Midwestern, Southwestern, and Western regions).
  • Retrospective or Prospective: Prospectively collected.

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

The document does not explicitly state the number or qualifications of "experts" used to establish the ground truth. The ground truth was established by bacterial C. difficile culture, which is a laboratory-based method. The performance of the culture itself would typically be overseen by trained laboratory personnel, but no specific "experts" for truth adjudication are mentioned outside of the methodology.

4. Adjudication method for the test set

There is no mention of an adjudication method like 2+1 or 3+1 for the clinical test set. The ImmunoCard C. difficile GDH assay results were directly compared to the results of bacterial C. difficile culture.

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

A Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This is not an AI-based device, but rather a rapid qualitative enzyme immunoassay (EIA) intended for screening.

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

This question is not applicable in the context of this device. The ImmunoCard C. difficile GDH is itself a "standalone" diagnostic test (an EIA) that produces a visual read (positive/negative) which is then interpreted by a human. There is no separate "algorithm only" performance reported, as the human interpretation of the visual reaction is an inherent part of the device's function.

7. The type of ground truth used

The type of ground truth used for the clinical performance comparison was bacterial C. difficile culture.

8. The sample size for the training set

The document does not explicitly mention a "training set" in the context of machine learning or AI. This is a traditional immunoassay. However, if we interpret "training set" as the samples used for initial development and optimization of the assay prior to clinical validation, that information is not detailed here. The analytical studies (sensitivity, interference, cross-reactivity, strain reactivity) involved various spiked and natural samples, but these are not referred to as a "training set" in the sense of a machine learning model.

9. How the ground truth for the training set was established

As there is no distinct "training set" described in the machine learning sense, the establishment of its ground truth is not applicable. For the analytical studies (e.g., sensitivity, cross-reactivity), the ground truth was established by:

• Known concentrations of C. difficile GDH antigen (for analytical sensitivity/limit of detection).
• Known presence or absence of specific microorganisms/substances (for interference and cross-reactivity studies).
• Confirmed C. difficile stock cultures (for strain reactivity).

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