Analytical and clinical comparison of anti-CCP assays with rheumatoid factor for the diagnosis of rheumatoid arthritis

Introduction: Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by chronic joint inflammation and extra-articular manifestations, eventually leading to permanent disability without early therapeutic interventions. Methods: The analytical and clinical performance of an electrochemiluminescent immunoassay (ECLIA) (Roche Diagnostics, Indianapolis, IN) were determined for cyclic citrullinated peptide antibodies (anti-CCP) in the diagnostic assessment of rheumatoid arthritis compared to a plate-based anti-CCP enzyme immunoassay (EIA) (Inova Diagnostics, Inc.). Results: Imprecision studies on the automated Roche ECLIA demonstrated intra-assay CV's of <. 3% and inter-assay CV's of <. 7%. The Inova EIA had intra-assay CV's of <. 15% and inter-assay CV's of <. 12%. The limit of quantitation of both assays was acceptable, and both assays showed similar linearity within the manufacturer's defined reportable ranges. Overall, analytical concordance was 62%, with 95.2% positive and 53.2% negative concordance. The clinical specificity in a normal population (n. =. 91) was 98.9% and 100% for Roche ECLIA and Inova EIA, respectively. The clinical specificity in a connective tissue disease population (n. =. 98) was 91.9% (95%CI, 86.0 to 96.5%) and 88.8% (95% CI, 81.0 to 93.6%) for Roche ECLIA and Inova EIA, respectively. Conclusion: The Roche ECLIA demonstrated similar analytical performance, although with improved intra-assay precision, in comparison to the Inova EIA. The two methods also demonstrated similar clinical sensitivity and specificity. The Roche automated immunoassay is a viable alternative to the plate-based EIAs with the advantage of being performed on an automated platform.