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Licensed Unlicensed Requires Authentication Published by De Gruyter March 19, 2010

Diagnostic performance of anti-citrullinated peptide antibodies for the diagnosis of rheumatoid arthritis: the relevance of likelihood ratios

  • Donatello Pietrapertosa , Barbara Tolusso , Elisa Gremese , Maria Concetta Papalia , Silvia Laura Bosello , Giusy Peluso , Luca Petricca , Alessandro Michelutti , Francesca Faustini , Anna Laura Fedele and Gianfranco Ferraccioli


Background: The goal of our study was to evaluate the diagnostic performance of the anti-cyclic citrullinated peptide 2 (anti-CCP2) assay in patients with autoimmune and inflammatory disorders.

Methods: We tested the specificity and sensitivity of anti-CCP2 antibodies measured by ELISA in 787 patients with rheumatoid arthritis (RA), 1024 patients with other autoimmune/inflammatory rheumatic disease and 401 subjects without autoimmune rheumatic disease. The optimal cut-off value was defined as the value with the highest diagnostic accuracy (receiver operating characteristic curve analysis). Interval-specific likelihood ratios (LRs) were calculated for each range bounded by defined anti-CCP2 values.

Results: To distinguish between patients with RA and controls, the cut-off value with the highest diagnostic accuracy for anti-CCP2 was 2.8 U/mL. Comparing the optimal cut-off value for anti-CCP2 to that recommended by the manufacturer (5.0 U/mL), an increase in prevalence between the proportions of test-positive patients was found for RA, undifferentiated connective tissue disease and undifferentiated arthritis. Evaluating interval-specific LRs for the selected ranges bound by two anti-CCP2 values, in RA and diseased controls, the LRs were 0.40 for values <5.0 U/mL, 6.66 for 5.0–15.0 U/mL, 27.01 for 15.1–30.0 U/mL and 28.89 for >30.0 U/mL.

Conclusions: The cut-off value of 2.8 U/mL for anti-CCP2 has the highest diagnostic accuracy. A value of anti-CCP2 >15 U/mL is associated with an increase in the likelihood of RA disease.

Clin Chem Lab Med 2010;48:829–34.

Corresponding author: Gianfranco Ferraccioli, MD, Professor of Rheumatology, School of Medicine, Catholic University of the Sacred Heart, Via Moscati 31, 00168, Rome, Italy

Received: 2009-11-24
Accepted: 2010-1-17
Published Online: 2010-03-19
Published in Print: 2010-06-01

©2010 by Walter de Gruyter Berlin New York

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