title: Anti-CCP and antikeratin antibodies in rheumatoid arthritis, primary Sjögren's syndrome, and Wegener's granulomatosis.
abstract: The objective of this study was to investigate the frequency of antibodies against cyclic citrullinated peptides (anti-CCP) and keratin (AKA) in patients with rheumatoid arthritis (RA) as well as in patients with primary Sjögren's syndrome (pSS) and Wegener's granulomatosis (WG), who may present with rheumatoid factor (RF)-positive arthritis. The study group consisted of 46 patients with RA (26 patients were negative for RF), 32 with pSS, 22 with WG, and 40 healthy controls. The RF, anti-CCP, and AKA were detected in serum using the latex agglutination test, enzyme-linked immunosorbent assay, and indirect immunofluorescence, respectively. The agreement between those tests was evaluated by kappa test. No positive result for AKA was detected in pSS and WG patients, and anti-CCP was found in only one patient with pSS. The results of kappa tests were low, varying between 0.25 (RF-anti-CCP) and 0.02 (RF-AKA). The sensitivity and specificity values were 43 and 44% for RF, 65 and 98% for anti-CCP, and 58 and 100% for AKA, respectively, in RA patients. In the RF-negative RA group, AKA was found to have a high frequency (55%) in comparison to anti-CCP (38%). Seropositivity was found to be 87% for any one of the three autoantibodies tested in RA patients. With a higher specificity, values for RA, anti-CCP, and AKA seem to be helpful for the differential diagnosis of patients with RF-positive arthritis, which may include patients with WG and pSS, and screening of all three antibodies may increase the diagnostic performance.
authors.forename: Sevil
authors.initials: S
authors.lastname: Kamali
authors.forename: Nuray Gurel
authors.initials: NG
authors.lastname: Polat
authors.forename: Esen
authors.initials: E
authors.lastname: Kasapoglu
authors.forename: Ahmet
authors.initials: A
authors.lastname: Gul
authors.forename: Lale
authors.initials: L
authors.lastname: Ocal
authors.forename: Orhan
authors.initials: O
authors.lastname: Aral
authors.forename: Meral
authors.initials: M
authors.lastname: Konice
authors.forename: Selim
authors.initials: S
authors.lastname: Badur
authors.forename: Murat
authors.initials: M
authors.lastname: Inanc
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D005260:Female; D014890:Granulomatosis with Polyangiitis / Q000175:diagnosis / Q000276:immunology*; D006801:Humans; D007633:Keratins / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D015203:Reproducibility of Results; D012217:Rheumatoid Factor / Q000097:blood; D012680:Sensitivity and Specificity; D012859:Sjogren's Syndrome / Q000175:diagnosis / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D007633:Keratins; D012217:Rheumatoid Factor