Antifilaggrin antibodies in recent-onset arthritis

We evaluated the sensitivity and prognostic value of an enzyme-linked immunosorbent assay (ELISA) for the measurement of antifilaggrin antibodies (AFA), using filaggrin purified from human skin as an antigen. The AFA test was applied to a series of 306 patients with various recent-onset inflammatory joint diseases. The results were compared to those of the conventional immunofluorescence tests for antikeratin antibody (AKA) and antiperinuclear factor (APF) and of the rheumatoid factor (RF) tests from a previous study. There was a very good agreement between the results of the tests for APF and AFA (kappa-value 0.79 in patients with peripheral poly/oligoarthritis). The agreement between the tests for AKA and AFA was significant but less pronounced (kappa-value 0.50). The AFA test detected 10/22 of the RF-negative erosive cases, particularly those with a large number of erosive joints. Thus, the test for AFA supplements RF in the prediction of erosiveness.