Short communication Analytical and clinical comparison of anti-CCP assays with rheumatoid factor for the diagnosis of rheumatoid arthritis Darci R. Block a, ⁎, Sarah M. Jenkins b , Daniel A. Dalenberg a , Joseph G. Balsanek a , Melissa R. Snyder a , Amy K. Saenger a a Mayo Clinic, Department of Laboratory Medicine and Pathology, 200 First Street SW, Rochester, MN 55905, USA b Mayo Clinic, Department of Health Sciences Research, 200 First Street SW, Rochester, MN 55905, USA abstract article info Article history: Received 28 October 2011 Received in revised form 2 February 2012 Accepted 3 February 2012 Available online 14 February 2012 Keywords: Anti-CCP Enzyme immunoassay (EIA) Electrochemiluminescent immunoassay (ECLIA) Analytical performance 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 immunoas- say (EIA) (Inova Diagnostics, Inc.). Results: Imprecision studies on the automated Roche ECLIA demonstrated intra-assay CV's of b 3% and inter- assay CV's of b 7%. The Inova EIA had intra-assay CV's of b 15% and inter-assay CV's of b 12%. The limit of quan- titation 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 sensitiv- ity 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. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Rheumatoid arthritis (RA) afflicts up to 1% of the world's popula- tion, affecting females to a greater extent (3–5 fold) than males [1]. Currently the diagnosis of RA is made through assessment of clinical symptoms, autoantibody serology [2] including rheumatoid factor (RF), and acute phase reactants such as C-reactive protein (CRP), both of which are moderately sensitive but lack clinical specificity and do not detect early asymptomatic disease. Anti-cyclic citrulli- nated peptide (anti-CCP) antibodies are IgG autoantibodies which recognize citrullinated peptides and offer improved specificity in early diagnosis of RA compared to RF [3]. Anti-CCP assays are tradi- tionally performed utilizing plate-based ELISA and are available from a variety of manufacturers, however random access analyzers offer the advantage of optimized work flows and improved turn- around times [4]. 2. Materials and methods Assays were performed according to the manufacturer's package in- serts. The Quanta Lite™ CCP 3.1 (Inova Diagnostics, Inc., San Diego, CA) anti-CCP ranges are reported as follows: strong positive: ≥60.0 U/ml, positive: 40.0–59.9 U/ml, weak positive: 20.0–39.9 U/ml, negative: b 20.0 U/ml. The Roche (Modular E170 Roche Diagnostics, Indianapolis, IN) anti-CCP results were classified as either positive (≥17.0 U/ml) or negative (b 17.0 U/ml). This assay is considered second generation uti- lizing a set of cyclic citrullinated peptide antigens. The reportable ranges are up to 250 U/ml and 500 U/ml for the Inova and Roche assays, respec- tively. The Inova EIA is a plate-based method where specimens are batched in our laboratory into runs of 80 samples that require 3 h to process and read on an automated Triturus (Grifols, Los Angeles, CA) platform. The time to first result from receipt in the lab under optimal circumstances is 3 h, but may be much longer depending on time Clinica Chimica Acta 413 (2012) 1015–1017 Abbreviations: RA, rheumatoid arthritis; RF, rheumatoid factor; CCP, cyclic citrulli- nated peptide; CTDs, connective tissue diseases; ACR/EULAR, American College of Rheumatology/European League Against Rheumatism. ⁎ Corresponding author at: Mayo Clinic, Hilton 03_70 B, 200 First Street SW, Rochester, MN 55905, USA. Tel.: +1 507 284 2511; fax: +1 507 538 7060. E-mail address: Block.Darci@mayo.edu (D.R. Block). 0009-8981/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.cca.2012.02.002 Contents lists available at SciVerse ScienceDirect Clinica Chimica Acta journal homepage: www.elsevier.com/locate/clinchim