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For the quantitative detection of RF IgM-class antibodies in human serum by indirect enzyme immunoassayas an aid in the diagnosis of rheumatoid arthritis (RA). This test kit can be used either manually or in conjunction with the MAGO® Plus Automated EIA Processor.

The Is-Rheumatoid Factor Test Kit System is an enzyme-linked immunosorbent assay (ELISA) for the detection and quantitation of RF IgM-class in human serum.

Acceptance Criteria and Device Performance for Is-Rheumatoid Factor Test System

This document outlines the acceptance criteria and the results of studies demonstrating the performance of the Diamedix Is-Rheumatoid Factor Test System, an enzyme-linked immunosorbent assay (ELISA) for the detection and quantitation of IgM-class Rheumatoid Factor (RF) in human serum.

1. Acceptance Criteria and Reported Device Performance

The acceptance criteria for the Is-Rheumatoid Factor Test System were established through comparative studies against another commercially available EIA kit and nephelometry, as well as an assessment of linearity, cross-reactivity, precision, and expected values in normal and clinical populations.

2. Sample Sizes and Data Provenance

• Relative Sensitivity and Specificity vs. Another EIA Test:
  • Sample Size: 185 retrospective sera.
  • Data Provenance: Not explicitly stated, but implies a collection from a clinical setting, likely within the US given the FDA submission. Retrospective.
• Correlation with Nephelometry Results:
  • Sample Size: 40 samples.
  • Data Provenance: Not explicitly stated, but implies a collection from a clinical setting, likely within the US. Retrospective.
• Comparison with Latex Agglutination:
  • Sample Size: 71 sera (40 normal, 18 known clinical, 13 containing other autoantibodies).
  • Data Provenance: Not explicitly stated, but implies a collection from a clinical setting, likely within the US. Retrospective.
• Lack of Cross-reactivity with Other Antinuclear Antibodies:
  • Sample Size: 21 RF-negative samples (5 SSA, 4 Sm, 5 RNP, 3 Scl-70, 4 Jo-1, 3 dsDNA, 1 SSB).
  • Data Provenance: Not explicitly stated, but implies a collection from a clinical setting, likely within the US. Retrospective.
• Lack of Prozone/High-Dose Hook Effects:
  • Sample Size: 8 sera.
  • Data Provenance: Not explicitly stated, but implies a collection from a clinical setting, likely within the US. Retrospective.
• Correlation of Manual and MAGO Plus Results:
  • Sample Size: 303 normal and clinical serum samples.
  • Data Provenance: Not explicitly stated, but implies a collection from a clinical setting, likely within the US. Retrospective.
• Precision:
  • Sample Size: 6 serum samples of varying reactivity, plus kit Calibrator and controls.
  • Data Provenance: Reference materials and likely internal samples for method validation.
• Expected Values (Normal Population):
  • Sample Size: 118 blood donors.
  • Data Provenance: South Florida, USA; prospective collection (implied by "normal healthy population were assessed by testing sera").
• Expected Values (Clinical Population):
  • Sample Size: 93 sera from patients with a diagnosis of rheumatoid arthritis.
  • Data Provenance: Not explicitly stated beyond "patients with a diagnosis of rheumatoid arthritis", but likely USA and retrospective.

3. Number of Experts Used to Establish Ground Truth and Their Qualifications

The studies described are for an in-vitro diagnostic (IVD) device that measures a biomarker (RF IgM). The "ground truth" for the test sets in this context is based on:

• Established clinical diagnosis of Rheumatoid Arthritis (RA) for the clinical population. The number of experts or their qualifications for establishing these diagnoses are not specified in the document, as this is typically provided as pre-classified samples.
• Pre-classification by other established assays: "another commercially available EIA kit for detecting RF," "nephelometry," and "latex agglutination test." These methods themselves serve as the reference standard or "ground truth" for comparative performance. The expertise involved in generating these reference results is inherent in the validation of those comparator methods.
• Known normal healthy individuals: for the normal population. The "ground truth" for these samples is the absence of RA or high RF levels based on their healthy status.

No adjudication method using additional experts for these studies is described, as the comparison is primarily analytical against other assays or established clinical conditions.

4. Adjudication Method

Not applicable. The studies are analytical performance evaluations against other assays or established clinical classifications, not typically requiring external expert adjudication of results. The "ground truth" is derived from the established methods or patient diagnosis.

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

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This is an in-vitro diagnostic device, not an imaging AI diagnostic device where MRMC studies are common to assess human reader performance with and without AI assistance. The device is intended to provide a quantitative measurement of RF, which is then interpreted by clinicians.

6. Standalone (Algorithm Only) Performance Study

Yes, the studies presented primarily represent "standalone" performance (algorithm only without human-in-the-loop performance) of the Is-Rheumatoid Factor Test System. The device directly measures RF IgM levels in serum, and its performance (sensitivity, specificity, correlation, precision, etc.) is evaluated without direct human interpretation of raw assay data. The results (IU/ml values) are then provided to healthcare professionals for interpretation in the context of a patient's clinical picture.

There is also a comparison between manual and MAGO Plus Automated EIA Processor results, demonstrating the equivalence of the automated process, which is also a standalone algorithmic process.

7. Type of Ground Truth Used

The type of ground truth used varies by study:

• Clinical Diagnosis: For studies involving "clinical samples" or "patients with a diagnosis of rheumatoid arthritis," the ground truth is based on the diagnosis of rheumatoid arthritis.
• Results from Predicate or Reference Assays:
  • "another commercially available EIA kit for detecting RF"
  • "nephelometry"
  • "latex agglutination test"
  • These comparator methods served as the reference standard for relative sensitivity, specificity, and correlation.
• Known Healthy Status: For "normal samples" or "blood donors," the ground truth is their healthy status and presumed absence of elevated RF.
• Known Autoantibody Status: For the cross-reactivity study, samples were "RF-negative samples (as determined by testing in an commercially available RF kit) containing various ANA," where the presence and specificity of other ANAs were the known ground truth.

8. Sample Size for the Training Set

This submission describes the validation studies for a diagnostic assay, not a machine learning algorithm that requires a "training set" in the conventional sense. The "development" or "optimization" of the assay kit components would involve internal studies, but these are not explicitly described as a distinct "training set" with specific sample sizes in this 510(k) summary. The provided sample sizes are for performance validation studies.

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

As noted above, this device is an IVD biochemical assay and not an AI/ML algorithm that leverages a "training set" in the typical manner. Therefore, the concept of establishing ground truth for a training set does not directly apply here. The "ground truth" mentioned in the validation studies (e.g., clinical diagnosis, results from other assays) is used for testing and validating the assay's performance, not for training an underlying model.

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