Clinical Aspects of the Dense Fine Speckled Pattern in Indirect Immunofluorescence-Antinuclear Antibody Screening and Its Association with DFS70 Autoantibodies

The existence of anti-dense fine speckled (DFS) 70 autoantibodies are considered an exclusionary biomarker for systemic autoimmune rheumatic diseases (SARDs). Several tests to confirm the presence of anti-DFS70 autoantibodies have been introduced, and the use of them in specimens with a DFS pattern in indirect immunofluorescence-antinuclear antibody (IIF-ANA) testing has been suggested. However, these additional tests have only been evaluated in a small number of samples; their clinical usefulness therefore requires further evaluation. A total of 213 serum specimens showing DFS (n=155) or homogeneous (H; n=58) patterns were included. All specimens were tested by western blotting (WB) and enzyme immunoassay (EIA). Clinical information regarding SARDs was analyzed. The detection rates for WB and EIA for anti-DFS70 autoantibodies in specimens with a DFS pattern were 86.5% and 73.5%, respectively. Detection rates in specimens with a low IIF-ANA titer were significantly lower than those in specimens with a high titer. The detection rate of anti-DFS70 autoantibodies in 58 specimens with an H pattern was 10.3% (6/58). Among 155 subjects with a DFS pattern in IIF-ANA staining, only five were diagnosed with SARD. There is little need to confirm the presence of anti-DFS70 autoantibodies using other methods. When a DFS pattern is observed in IIF-ANA staining, it is more important to confirm the presence of other autoantibodies related to SARDs than to identify anti-DFS70 autoantibodies. Finally, more careful interpretation of IIF-ANA to specimens with a low IIF-ANA titer is needed.