Objectives: Whereas antinuclear antibodies (ANAs) detected by indirect immunofluorescence (IIF) have diagnostic significance, the dense fine speckled (DFS) pattern on HEp-2 cells may be an exclusionary marker for ANA-associated rheumatic disease (AARD). The aim of this study was to evaluate a new algorithm considering anti-DFS70 antibodies for routine ANA testing.
Method: From ANA requested sequential 10 528 sera, 181 sera samples showing the DFS pattern were additionally tested for anti-DFS70 antibodies by an enzyme-linked immunosorbent assay (ELISA-DFS70) and for specific-ANAs. Specific-ANAs(+)/IIF-DFS(-) control sera samples (n = 50) were also tested.
Results: Of the 181 IIF-DFS-positive sera samples, 82.9% (n = 150) were from non-AARD patients and 112 (61.9%) patients had non-rheumatic diseases (NRD), including the most common clinical feature of dermatitis (18.2%). The ELISA-DFS70 was positive in 109 (60.2%) sera and was negative in all control sera. Specific-ANAs were similarly detected as 25.7% (28/109) and 22.2% (16/72) of ELISA-DFS70(+) and ELISA-DFS70(+) patients, respectively (p > 0.05). The prevalence of non-AARD was 95.1% and 25.1% in the ELISA-DFS70(+)/specific-ANAs(-) and ELISA-DFS70(-)/specific-ANAs (+) groups, respectively.
Conclusions: In patients with a HEp-2 DFS pattern, the additional ELISA-DFS70 and specific-ANAs test could improve the efficiency of diagnosing AARD. The detection of anti-DFS70 antibodies should be included in test algorithms for ANA testing.