ABSTRACT
OBJECTIVE: To assess the diagnostic and prognostic power of antiperinuclear factor (APF) and to identify a specific pattern of rheumatoid arthritis (RA) of different evolution and prognosis. METHODS: One hundred and fifty-nine sera from patients with RA, 280 sera from patients with other rheumatic diseases and 204 sera from healthy subjects were examined for APF. RESULTS: Sensitivity and specificity of the test were, respectively, 0.82 and 0.99 when 1:80 serum dilution was considered positive but 0.84 and 0.92 when tested at the currently used 1:5 serum dilution. According to the data obtained from APF and rheumatoid factor (RF) testing, patients with RA were subdivided in 4 groups. Clinical and demographic features for each group were analyzed. RF+ and/or APF+ patients showed a common pattern of disease, whereas RF-/APF- patients showed fewer extraarticular manifestations (p < 0.02) including Sjögren's syndrome (p < 0.04) and an unusual onset of the disease characterized by an involvement of large joints (p < 0.0001). Higher titer of APF was detected at the onset of the disease than in longstanding RA (p < 0.02). CONCLUSIONS: APF is a valuable diagnostic tool and a useful additional marker for RA. 1:80 serum dilution allows more specificity without substantial loss of sensitivity. A specific pattern of RA can be identified on the basis of APF status.
