Investigation of the diagnostic value of anti-dense fine speckled 70/lens epithelium derived growth factor p75 autoantibody for autoimmune diseases

Abstract

Antinuclear antibodies (ANA) are the autoantibodies that are produced against nuclear antigens in the cell nucleus and/or cytoplasm, and are one of the important diagnostic criteria in systemic autoimmune rheumatic diseases (SARD). Until today, several methods have been developed for detecting ANA's. However, indirect immunofluorescence (IIF) technique, that is also known as one of the oldest methods, is still the most commonly used one. Typically, anti-dense fine speckled 70/Lens epithelium derived growth factor p75 (anti-DFS70/LEDGF p75) autoantibody can be detected via IIF method where in HEp-2 (human larynx carcinoma) cells are used. The dense fine speckled (DFS) pattern method can be masked and remain unnoticed by the IIF method when it exists with the other ANA. Anti-DFS70 autoantibodies seldomly appear in SARD patients compared to healthy individuals. Moreover, these antibodies may appear in different chronic inflammatory conditions like interstitial cystitis, chronic fatigue syndrome, atopic dermatitis and Vogt-Koyanagi-Harada syndrome. The aim of this study was to determine the frequency of anti-DFS70 autoantibodies by immunblot (IB) method in patients sera with and without DFS70 staining pattern by IIF and to determine if the presence of anti-DFS70 has a clinical impact when included in ANA testing algorithm. In our study, a total of 60 patients' sera in which DFS pattern was defined by IIF method and 67 patients' sera in which other patterns observed were included in the study and anti-DFS70 autoantibody was investigated by IB method in these sera. In 67 patient samples which have shown the other patterns three (4.5%) samples were determined to be anti-DFS70 positive by IB. In 55 patients who were determined to have IIF-DFS pattern (+)/IB anti-DFS70 (+), 6 (11%) were diagnosed as SARD and the other antinuclear antibodies (ANA) were found as negative by IB. In the other group with the other ANA patterns detected, none of the SARD-diagnosed 22 patients had shown anti-DFS70 by IB method. Sixteen (26.6%) samples in the group that was positive for the IIF-DFS pattern were obtained from rheumatology and physical therapy and rehabilitation clinics, 32 (47.7%) samples were from the group in which other patterns observed and were also obtained from those clinics. DFS pattern was detected significantly more frequent in the samples from other clinics in comparison to the samples from rheumatology and physical therapy and rehabilitation clinics (p= 0.018). In our study, it was concluded that DFS pattern can be defined by IIF method by only specialists, however, since homogeneous-like and mixed patterns can be confused especially in low titers, there is a need for a second well-validated immunological test that could detect anti-DFS70 auto-antibody.