Background: This study aimed to evaluate the overall diagnostic value of citrullinated or carbamylated fibrinogen antibodies in patients with rheumatoid arthritis (RA).
Methods: Serum samples collected from 114 patients with established RA, 143 patients with non-RA diseases, and 200 healthy controls were tested by ELISA for citrullinated fibrinogen (Cit-fib), carbamylated fibrinogen (Ca-fib), and chimeric fibrinogen a/b chain citrullinated peptides (CFABCP). Diagnostic indexes and correlations with titers were calculated, cross reactivities of Cit-fib, Ca-fib, and CFABCP were assessed by competition experiments.
Results: With a cutoff ensuring 98% specificity for RA patients versus healthy controls, the sensitivities of Cit-fib and Ca-fib are 66.67% and 24.6%, respectively, while the sensitivity of CFABCP was 74.56%. Cit-fib, Ca-fib, and CFABCP can inhibit reciprocally in competition experiments. As for non-RA patients, the positive rate of Ca-fib was higher than that of Cit-fib and CFABCP.
Conclusions: Citrullination and carbamylation of fibrinogen both have a role in RA diagnosing, but citrullination is better. The recombination of peptides, CFABCP, has high specificity and considerable sensitivity for diagnosis for RA patients.