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The C4 assay is used for the quantitation of C4 in human serum or plasma. Complement is a group of serum proteins which destroy infectious agents. Measurement of these proteins aids in the diagnosis of immunologic disorders, especially those associated with deficiencies of complement components.

C4 is an in vitro diagnostic assay for the quantitative determination of C4 in human serum or plasma. Antigen in the sample bonds to the specific antibody in the reagent, forming an immune complex. The immune complex causes an increase in light scattering, measured by reading turbidity at 604 nm, which correlates with the concentration of C4 in the sample.

Here's an analysis of the provided text regarding the C4 assay's acceptance criteria and the study proving its performance:

Considering the nature of the device (an in vitro diagnostic assay for quantitative C4 determination), some of the requested information (like multi-reader multi-case studies, ground truth established by experts like radiologists, or pathology) are not directly applicable to this type of medical device. The focus for IVD assays is typically on analytical performance characteristics and comparison to a predicate device.

Acceptance Criteria and Reported Device Performance

Study Details

1. Sample Size Used for the Test Set and Data Provenance:

   • The document states "Comparative performance studies were conducted." However, the exact sample size for the method comparison or precision studies (e.g., number of patient samples, number of replicates) is not explicitly mentioned in the provided summary.
   • Data Provenance: Not specified (e.g., country of origin, retrospective or prospective). Given the nature of a 510(k) submission for an in vitro diagnostic, it's highly likely to be prospective clinical laboratory testing.

2. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications:

   • Not applicable in the traditional sense for this type of in vitro diagnostic device. "Ground truth" for an IVD assay's analytical performance is typically established by:
     • Reference Methods: The predicate device itself (K-ASSAY C4 assay on Hitachi 717 Analyzer) serves as the "reference standard" against which the new device's performance is compared.
     • Control Materials: Certified or well-characterized control materials are used for precision studies.
     • Standard Analytical Procedures: Following established laboratory protocols for performing the tests.
   • There isn't a need for a panel of "experts" (like radiologists interpreting images) to establish ground truth for quantitative biochemical measurements in this context.

3. Adjudication Method for the Test Set:

   • Not applicable. Adjudication methods (like 2+1, 3+1) are typically used for subjective assessments (e.g., image interpretation) where multiple human readers disagree. For quantitative assays comparing numerical results, statistical methods like correlation coefficients, slope, and intercept are used for comparison, and precision is measured directly.

4. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:

   • No. This type of study is primarily relevant for imaging devices or other diagnostic tools where human interpretation plays a significant role and the benefit of AI assistance for human readers can be quantified. The C4 assay is an automated in vitro diagnostic test, so there is no "human reader" in the loop for interpretation in the same way.

5. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study:

   • Yes, effectively. The reported performance characteristics (correlation, precision, assay range, sensitivity) are inherently "standalone" as they describe the analytical performance of the C4 assay system (reagents and AEROSET™ Analyzer) without human interpretive input. The C4 assay is the algorithm/device under evaluation.

6. Type of Ground Truth Used:

   • For the method comparison, the "ground truth" was established by the results obtained from the legally marketed predicate device (K-ASSAY C4 assay on the Hitachi 717 Analyzer). This is a common form of "truth" for demonstrating substantial equivalence for new IVD devices.
   • For precision, the ground truth involves the known values of the control materials and the statistical calculation of variability from repeated measurements.

7. Sample Size for the Training Set:

   • Not applicable/Not mentioned. This device is an in vitro diagnostic assay, not an AI/Machine Learning algorithm that undergoes a "training phase" in the traditional sense. The development of such assays involves reagent formulation, instrument calibration, and optimization based on chemical and analytical principles, not on "training data" for a learning algorithm.

8. How the Ground Truth for the Training Set Was Established:

   • Not applicable for the reasons stated above. There isn't a "training set" with established ground truth in the context of this chemical assay.

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