Anti-dense Fine Speckled 70 Autoantibodies in Japanese Children with Dermatomyositis, Localized Scleroderma, and Idiopathic Arthritis with Iridocyclitis

Low Prevalence of Anti-DFS70 Antibodies in Children With ANA-Associated Autoimmune Disease

INTRODUCTION

Anti-DFS70 antibodies occur in healthy individuals with various medical conditions. Unlike other anti-nuclear autoantibodies (ANA), they are not associated with systemic autoimmune disease in adult patients. To date, only a few studies have addressed the prevalence and/or clinical relevance of anti-DFS70 autoantibodies in children with and without autoimmune disease.

METHODS

Included in this retrospective cross-sectional mono-centric study were 308 pediatric patients with suspected or known autoimmune conditions who had a positive ANA in indirect immune fluorescence (IIF) screening and who were screened for anti-DFS70 antibodies by extractable nuclear antigen antibodies (ENA) immunoblot. Patients were assigned to four different diagnostic categories according to their diagnosis in the corresponding medical record: (a) absence of autoimmune or rheumatic disease (noARD, n = 116); (b) suspected autoimmunity without definitive diagnosis (sAI, n = 48); (c) other rheumatic disease (ORD) (n = 115); and (d) ANA-associated autoimmune disease (AARD, n = 29).

RESULTS

The prevalence of anti-DFS70 antibodies in the overall cohort was 33.8%. Among children without ARD (46.6%, 54/116), prevalence was significantly higher than among children with ORD (23.7%, 27/115, p = 0.0003) or AARD (17.2%, 5/29, p = 0.0054). Among all of the anti-DFS70 positive patients with AARD, other autoantibodies were found in the ENA immunoblot. In contrast, among anti-DFS70 positive patients with ORD (11.5%, 4/27), sAI (33.3%, 6/18) and noARD (16.7%, 9/54), other autoantibodies infrequently were detected (p = 0.0005). Patients with uveitis rarely were positive for anti-DFS70 antibodies (7.7%, 1/13). No association was found between anti-DFS70 antibodies and a history of allergic conditions (p = 0.51). The concordance between a typical DFS pattern in IIF and the detection of anti-DFS70 antibodies by immunoblot was 59.3%.

CONCLUSION

As with adults, the higher prevalence of anti-DFS70 among children without autoimmune disease confirms the mutual exclusion for this autoantibody in the pathogenesis of ARD. Among ANA-positive children, monospecific anti-DFS70 antibodies may help to discriminate between AARD and not-AARD-related conditions.

Clinical significance of anti-DFS70 antibody in antinuclear antibody-positive samples with a dense fine speckled pattern

Background

When the dense fine speckled (DFS) pattern-antinuclear antibodies (ANA) are detected in the indirect immunofluorescence (IIF) assay, the presence of anti-dense fine speckles 70 (DFS70) antibodies has been suggested to facilitate the exclusion of ANA-associated rheumatic diseases (AARD). We evaluated the potential use of anti-DFS70 antibodies for verifying AARD in patients with a positive ANA result of the DFS pattern.

Methods

A total of 5509 patients who were requested ANA testing were included. The DFS pattern was confirmed using two IIF assays. Semiquantitative DFS70 ELISA (Euroimmun, Germany) was examined in samples with the DFS pattern.

Results

Among 639 ANA-positive patients, 19.6% displayed the DFS pattern. And 17.6% of patients with the DFS pattern were diagnosed with AARD. The low titer of 1:80 was more prevalent in the non-AARD group than in the AARD group (64.1% vs. 4.5%, p < 0.0001). Anti-DFS70 antibodies were positive in 60.0% of patients with the DFS pattern. The frequency of anti-DFS70 positivity was higher in the non-rheumatic disease (NRD) group (74.2%) than in the other rheumatic disease group (43.2%, p = 0.003) and the AARD group (45.5%, p = 0.019).

Conclusions

The DFS pattern is present in both AARD and non-AARD cases. In the DFS pattern, a low titer of 1:80 and isolated anti-DFS70 antibodies without AARD-associated antibodies represent a low likelihood of AARD. The presence of anti-DFS70 antibodies cannot exclude AARD and should be analyzed in combination with AARD-associated antibodies in the diagnostic algorithm.