Background/Purpose: Autoantibodies to the dense fine speckled 70 (DFS70) antigen are common among ANA (dense fine speckled pattern) positive healthy individuals and consequently reduce the specificity of the ANA test. This might lead to miss-diagnosis, unnecessary referral, increased healthcare expenditure and even miss-treatment. Therefore, the reliable identification of anti-DFS70 antibodies is of high importance. Recently, different methods were developed to identify samples containing anti-DFS70 antibodies including a chemiluminescence assay (CIA) for the detection of anti-DFS70 antibodies and an indirect immunofluorescence (IIF) immunoadsorption technology which blocks anti-DFS70 antibodies from binding to the native ligand on HEp-2 cells. Here, we assessed the prevelance of anti-DFS70 antibodies in patients with and without systemic autoimmune rheumatic diseases (SARDs) and compared two methods for the detection of these antibodies: IIF and CIA.

Methods: We evaluated 51 ANA-positive sera samples from patients with confirmed clinical diagnosis of SARD, 92 samples from healthy blood donors and 85 samples submitted to a reference laboratory for routine ANA testing. These samples were tested by QUANTA Flash DFS70 CIA on the BIO-FLASH instrument (Inova Diagnostics, San Diego, USA) to measure anti-DFS70 antibodies, and were evaluated by automated IIF (NOVA Lite HEp-2 Select, Inova Diagnostics, USA). Samples were tested with and without DFS70 inhibition. Mono-specificity of anti_DFS70 antibodies was define by successful and complete inhibition of ANA reactivity by the DFS70 antigen in the HEp-2 Select sample buffer.

Results: 24 samples (10.5%) tested by QUANTA Flash DFS70 CIA were positive for anti-DFS70 antibodies. The prevalence of monospecific anti-DSF70 antibodies was significantly higher in healthy subjects than in patients with SARDs (10.2% vs 1.9%, p=0.02). The frequency of anti-DFS70 antibodies in samples submitted to a reference laboratory for routine ANA testing was 27%. A very good agreement was found between QUANTA Flash DFS70 CIA and the DFS pattern identified by automated HEp-2 IIF (kappa=0.97). In 80% of the samples obtained from patients without SARDs, HEp-2 Select Kit effectively inhibited the anti-DFS70 antibodies, reducing false positive ANA results.

Conclusion: Our data confirm that mono-specific anti-DFS70 antibodies are a strong discriminator between ANA positive healthy individuals and SARD patients. In addition, anti-DFS70 antibodies are very common in ANA routine samples. Consequently, the detection of anti-DFS70 antibodies should be included in ANA testing algorithms to aid in the interpretation of ANA positivity without underlying SARD. In addition, anti-DFS70 antibodies should be considered for future revisions of disease classification criteria.

« Back to 2016 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-anti-dfs70-antibodies-in-patients-with-and-without-systemic-autoimmune-rheumatic-diseases/