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The INCSTAR CMV IgG "fast" ELISA Kit contains instructions and materials for the qualitative and/or semi-quantitative detection of IgG antibodies to cytomegalovirus in human serum by indirect enzyme-linked immunosorbent assay (ELISA) technique. When performed according to instructions, the CMV IgG "fast" ELISA test is of value in the determination of immunological response to infection with CMV. The evaluation of paired sera, acute and convalescent, by demonstrating seroconversion or a significant rise in antibody can aid in the diagnosis of primary infection, reactivated infection, or reinfection with cytomegalovirus.

The INCSTAR CMV IgG "fast" ELISA test kit utilizes the enzyme-linked immunosorbant assay (ELISA) technique for the detection of cytomegalovirus IgG antibodies. Polystyrene microtiter wells are coated with purified CMV antigen. Diluted patient serum is incubated with purified CMV antigen bound to the solid surface of a microtiter well. The CMV antibodies that are present in the patient's serum will be captured by the solid phase. After washing, these complexes bind with horseradish peroxidase labeled antihuman IgG which react with the addition of chromogen (tetramethylbenzidine), resulting in color development. The absorbance of the solution, measured at 450 nm, is directly proportional to the concentration of IgG antibodies to CMV antigen present in the reaction solution.

Acceptance Criteria and Device Performance Study for the INCSTAR CMV IgG “fast” ELISA Kit

This document describes the acceptance criteria and the study proving the device meets these criteria, based on the provided K955360 submission.

1. Acceptance Criteria and Reported Device Performance

The acceptance criteria are established relative to a predicate device, the GULL CMV IgG ELISA test (K915892).

Note: The acceptance criteria for sensitivity and specificity are not explicitly stated as distinct numerical targets but are inferred from the reported performance, which demonstrates substantial equivalence to the predicate device whose performance would have been previously established. The reported performance ranges (99-100% and 95-100%) indicate that the device met these implicit criteria.

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

• Sample Size: 308 serum samples, representing 296 individuals.
• Data Provenance: The document does not explicitly state the country of origin. The samples represent a "mixed population of healthy donors, immunocompromised hosts, transplant patients, and patients with other various illnesses," suggesting a diverse clinical setting. The study appears to be retrospective, as existing serum samples were collected and then tested.

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

The ground truth for the primary comparison was established by the predicate device (GULL CMV IgG ELISA Test). Therefore, no human experts were explicitly used for establishing the primary ground truth for the comparison.

However, for resolving discrepant results, a commercial CMV IgG ELISA assay was used. The number of experts involved in interpreting results from this resolving assay or their specific qualifications are not stated.

4. Adjudication Method for the Test Set

The primary adjudication method involved direct comparison with the predicate device (GULL CMV IgG ELISA Test). For samples with discrepant results between the INCSTAR device and the GULL device, a third commercial CMV IgG ELISA assay was used to resolve these discrepancies. This resembles a "tie-breaker" or discrepancy resolution method, where a third independent test provides further clarity.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not performed. This study evaluates diagnostic accuracy of an assay, not the effectiveness of human readers using the assay. Therefore, there is no effect size reported for human readers improving with AI vs. without AI assistance.

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

The INCSTAR CMV IgG "fast" ELISA Kit is a laboratory diagnostic assay, not an AI algorithm. Therefore, the concept of a "standalone" algorithm performance is not applicable in this context. The study inherently measures the performance of the assay itself.

7. The Type of Ground Truth Used

The primary ground truth for the clinical performance study was established by the results obtained from the predicate device: the GULL CMV IgG ELISA Test (K915892).

For discrepant samples, a third, commercial CMV IgG ELISA assay was used to further resolve the truth, implying that the ground truth for these specific cases was established by a consensus or "best available" assay result. This suggests a form of "expert consensus" not directly from human interpretation, but from a trusted, established laboratory method.

8. The Sample Size for the Training Set

The document does not specify a training set sample size. This is common for traditional diagnostic assays where the device's characteristics (e.g., reagent formulation, antibody specificity) are optimized during development, rather than "trained" in the machine learning sense. The clinical performance study described is an evaluation/validation study.

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

As there is no mention of a "training set" in the context of machine learning, the establishment of ground truth for such a set is not applicable. The development and optimization of such an ELISA kit would involve extensive laboratory work to ensure antigen-antibody specificity, sensitivity, and appropriate cut-offs, typically validated against known positive and negative samples, but not referred to as a "training set" with ground truth in the way AI models are.

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