Antibody to dense fine speckled 70 and its significance in a Sub-Himalayan population: A hospital-based study

Background: In antinuclear antibody (ANA) testing, antidense fine speckled 70 (DFS70) antibodies are commonly detected as a specific indirect immunofluorescence assay pattern (IIFA in HEp-2-based substrates) or as bands/blot lines in immunoblotting. A negative association between anti-DFS70 antibodies and the presence of autoimmune diseases is often reported. However, some studies found that this may not be true in females. We conducted this study to see the positivity rate of anti DFS70 antibodies and their association with other autoantibodies in the predominantly hilly population of our state. Methods: Serum samples sent for ANA testing between February 2018 and December 2020 were included. ANA IIFA-positive cases underwent immunoblot profiling with 16 targets (including DFS70) blotting kit. Those with DFS70 band in the immunoblot) underwent tests for other autoantibodies such as antineutrophil cytoplasmic antibodies, and anti-dsDNA. Association analysis was performed in a software package (SPSS version 23). Results: Out of 1770 samples, about 15.3% yielded a meaningful IIFA pattern. About 10.7% of ANA positives (1.6% of total samples) had the DFS70 band on immunoblotting. Isolated DFS70 was found in the predominantly male population (6 out of 7), while most females had this antibody in the presence of other autoantibodies (17 of 22). Conclusion: Male population had predominantly isolated anti DFS70 antibody detection (with the likely possibility of using it as a marker for the absence of autoimmune disease), while in females, mostly, it was along with other autoantibodies.