Serological Diagnosis Of Rheumatoid Arthritis. And Its Significance For Early Diagnosis

Objective To assess the diagnostic value (sensitivity and specificity) of antiperinuclear factor(APF), antikeratin antibody(AKA), anti-Sa antibody and anti-RA33/36 antibody in RA patients and to explore the significance of doing determinations of these 4 kinds of autoantibodies all at the same time in diagnosis of early RA. It is hoped that by improving the diagnosis of early RA and early institution of adequate treatments accordingly, the overall prognosis and outcome of RA would be favorably improved. Methods 600 serum samples, including 237 RA, 256 non-RA and 116 unspecified arthralgia/arthritis patients were studied for APF (immunofluorescence perinuclear granules on human buccal mucosa cell), AKA (immunofluorescence of plaque pattern on the stratum corneum of the Wistar rat esophagus), anti-Sa antibodies (immunoblotting on antigen prepared from placenta extracts ) and anti-RA33/36 antibodies (immunoblotting using antigens of both Hela cell extracts and Ehrlich ascites carcinoma cell extracts ).Results The sensitivity and specificity of APF for the diagnosis of RA were 48.67% and 91.57% respectively taking 1:20 as the positive titer; those of AKA were 44.13% and 89.01%, of anti-Sa were 36.68% and 91.55% and those of anti-RA33/36 ( using Ehrlich ascites carcinoma cells extracts ) were 34.76% and 89.76% respectively. The overall sensitivity and specificity of positive occurrence of at least one kind of the four autoantibodies were 82.81% and 67.92%, those of at least two kinds 54.17% and 91.32%, those of at least three kinds 24.49% and 99.62%, and those of all four kinds 2.55% and 100%o There was no correlation between the positive rate of the four kinds of autoantibodies and the duration of illness ,but all of them can be detected in RA patients with duration of illness less than one year. The positive rates of anti-Sa, APF, anti-RA33/36, AKA in those short duration RA patients were 47.37%, 42.11%, 28.57%, 15.69%, respectively. 116 patients of unspecified arthralgia/arthritis were studied and followed up for 4 ~ 18 months. At the end of follow-up period, 20 (68.97%) out of 29 APF positive patients were eventually diagnosed to have RA, 16(53.33%) out of 30 AKA positive and 19(48.72%) out of 39 anti-Sa positive patients were also eventually diagnosed...