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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.

Background: For the management of connective tissue disorders (CTDs), antinuclear antibody (ANA) testing is essential, both from diagnostic and prognostic points of view. Usually, patterns obtained by ANA-IIF testing correlates to specific autoantibodies as obtained from the test for ENA (by LIA/ELISA, etc.). But to apply these data from western studies, we may need validation in the local population like our subjects in sub-Himalayan (Garhwal region) area where CTDs are common. Also, suppose ANA-IFA pattern's correlation is reliably known in our population, it can minimize the cost of managing CTDs by limiting ENA testing, which is 10 times costlier than ANA-IIF. Hence, this study was undertaken to know the specific autoantibody targets (ENA by LIA) against ANA-IIF patterns in our local population. Materials and Methods: In this retrospective cross-sectional work, serum samples of CTDs were tested for ANA by IIF (Euroimmune AG) and ENA by LIA (Euroline ANA-3G) continuously for 36 months. The manufacturer's kit insert was followed, and results were analyzed applying appropriate statistical methods. Results: Major ANA-IIF patterns were found to be associated with specific autoantibodies, for example, Nuclear homogenous with dsDNA, nucleosomes, histones; speckled pattern with nRNP/Sm, Sm, SSA/Ro-52, SSB; nucleolar pattern with Scl-70, Pm-Scl 100 and centromere pattern with CENP-B. Anticytoplasmic (ACA) are found to be linked with some ANA negative (by IIF) samples, emphasizing the need for careful observation for ACA especially where ANA is not found. Conclusions: In most subjects, specific ENA targets correlated well with ANA-IIF patterns, implying effective cost minimization in CTD management. Similar future prospective studies (with clinical data) can provide a database and reference for our population.