Research article

Diagnostic value of anti-human citrullinated fibrinogen ELISA and comparison with four other anti-citrullinated protein assays

Bert Vander Cruyssen^1* , Tineke Cantaert^1* , Leonor Nogueira² , Cyril Clavel² , Leen De Rycke¹ , Amélie Dendoven¹ , Mireille Sebag² , Dieter Deforce³ , Christian Vincent² , Dirk Elewaut¹ , Guy Serre² and Filip De Keyser¹

¹  Department of Rheumatology, Ghent University Hospital, Ghent, Belgium

²  UMR 5165 'Laboratory of Epidermis Differentiation and Rheumatoid Autoimmunity', CNRS – Toulouse III University, Toulouse, France

³  Laboratory of Pharmaceutical Biotechnology, Ghent University, Ghent, Belgium

author email corresponding author email* Contributed equally

Arthritis Research & Therapy 2006, 8:R122doi:10.1186/ar2011

Published:	19 July 2006

Abstract

We studied the diagnostic performance of the anti-human citrullinated fibrinogen antibody (AhFibA) ELISA for rheumatoid arthritis (RA) in a consecutive cohort (population 1) and evaluated the agreement between the AhFibA ELISA and four other assays for anti-citrullinated protein/peptide antibodies (ACPAs) as well as rheumatoid factor in patients with longstanding RA (population 2). Population 1 consisted of 1024 patients with rheumatic symptoms; serum samples from these patients were sent to our laboratory for ACPA testing within the context of a diagnostic investigation for RA. Ninety-two of these patients were classified as having RA according to the American College of Rheumatology criteria and 463 were classified as non-RA patients. Population 2 consisted of 180 patients with longstanding RA and was used to assess agreement and correlations between five ACPA assays: anti-cyclic citrullinated peptide (CCP)1 and anti-CCP2 antibodies were detected using a commercially available ELISA, AhFibA using ELISA, and anti-PepA and anti-PepB antibodies using line immunoassay. Applying previously proposed cut-offs for AhFibA, we obtained a sensitivity of 60.9% and a specificity of 98.7% in population 1. Receiver operating characteristic curve analysis could not detect a significant difference in diagnostic performance between the AhFibA ELISA and anti-CCP2 assay. Performing a hierarchical nearest neighborhood cluster analysis of the five different ACPA assays in population 2, we identified two clusters: a cluster of anti-pepA, anti-pepB and anti-CCP1, and a cluster of AhFibA and anti-CCP2. In conclusion, we found that AhFibA and anti-CCP2 antibodies had similar diagnostic performance. However, disagreement between ACPA tests may occur.