COINCIDENCE OF AUTOANTIBODIES AMONG PATIENTS WITH DIFFUSE CONNECTIVE TISSUE DISORDERS

Abstract

Presence of some antinuclear antibodies (ANA)is a typical feature of connective tissue disorders (CTD), such as systemic lupus erythematosus (SLE), Sjogren’s syndrome, rheumatoid arthritis (RA). The purpose of our work was to estimate the significance of laboratory tests commonly used in CTD. We examines blood serum collected from 1312 patients with suspected connective tissue disorders, 105 patients with confirmed SLE, 163 patients with RA, 15 patient with Sjogren’s syndrome (SS), and 100 healthy volunteers. Blood serum was tested for antinuclear factor (ANF) using HEp-2 method, antibodies against extractable nuclear antigens (anti-ENA), line blot ANA, IgG antibodies against double-stranded DNA (anti-dsDNA IgG), IgG and IgM antibodies against cardiolipin (CL) and beta-2-glycoprotein 1 (B2GP1). The Crithidia luciliae immunofluorescence (CLIF) assay was also used to detect antibodies to native dsDNA. ANF prevalence in the patients with suspected CTD was 23,4% (309/1318). Speckled pattern of ANF was detected in 100% (15/15) of patients with SS. Prevalence of ANF in patients with SLE and RA was 79% and 36%, correspondingly. ANF was revealed only in 3% of healthy volunteers and its titer did not exceed 1/80. Blood serum from 282 patients was tested for ANF and anti-ENA. Coincidence of ANF and antibodies against ENA were found in 12% of cases (34/282), and isolated anti-ENA – in 7% of cases (20/282). In this group (anti-ENA-positive/ANF negative), antibodies to SS-A antigen were detected in 64% of patients, using ANA lineblot, 36% of patients were negative. Blood sera from 614 patients were tested, in order to evaluate coincidence of ANF and anti-dsDNA. The antibodies were revealed in 45.9% of cases, whereas a combination of ANF and anti-dsDNA in diagnostic titers was found in 151 patient. Anti-dsDNA in absence of ANF were detected in 14.9% (42/282) of patients; in 6.7% of the samples (19/282), higher concentrations of antibodies were detected (> 50 IU/ml). In conclusion, ANF sensitivity was 63% vs 35%, specificity – 89% vs 95% in the groups of patients with dsDNA antibodies, resp., > 25IU/ml, and > 50 IU/ml. In the patients examined for anti-CL, ANF and anti-dsDNA, high concentration of anti-CL without detectable ANF and anti-dsDNA was found only in one case; in the rest of patients, high titers of anti-CL were associated with higher titers of ANF and anti-dsDNA, thus indicating high probability of rheumatic diseases (most likely, SLE) in these patients. Informativity of the methods used for CTD diagnostics is increased, when several autoantibodies are detected concomitantly, thus allowing optimized immunological examination of the patients with rheumatic diseases.