Clinical significance of anti-dense fine speckled 70 antibodies in dense fine speckled immunofluorescence positive patients, systemic autoimmune rheumatic diseases, and controls
Rammohan Mylavarapu, Meghna Gavali, Kaushik Puranam, Bansi Kashyap Parejiya, Liza RajasekharBackground and objectives
The dense fine speckled (DFS) anti-nuclear antibody (ANA) pattern, caused by anti-DFS70 antibodies, is often misunderstood due to its low association with systemic autoimmune rheumatic diseases (SARD) and presence in healthy individuals. Few studies suggest monospecific anti-DFS70 antibodies may exclude SARD. Given limited data from India, we aimed to assess the prevalence and clinical associations of anti-DFS70 antibodies in undefined disease, SARD, and controls.
Methods
Sera from patients with undefined disease and non-rheumatic disease controls were screened for DFS pattern during the evaluation for ANA by indirect immunofluorescence (IIF); positive samples were confirmed using anti-DFS70 ELISA and line immunoassay (LIA). SARD sera were tested by ANA IIF, ELISA, and LIA.
Results
DFS IIF pattern was observed in 0.25%, 0.57% and 0.4% of undefined disease referrals, SARD patients, and controls respectively. ELISA anti-DFS70 and LIA were positive in 90% of undefined disease sera, 15.4% vs . 5.7% of SARD cases, and 100% of controls, respectively. ELISA and LIA showed almost perfect agreement in undefined disease (κ= 0.861). In SARD group, anti-DFS70 ELISA positivity was predominantly observed in SLE ( P =0.003); higher ELISA optical density, higher systemic lupus erythematosus disease activity index (SLEDAI) scores ( P <0.001), anti-dsDNA ( P =0.0001), and renal involvement ( P =0.014) being significant observations. Monospecific anti-DFS70 antibodies by LIA were significantly common in undefined disease ( P <0.001).
Interpretation and conclusions
DFS pattern with monospecific anti-DFS70 antibodies suggests lower likelihood of SARD. Anti-DFS70 antibodies are uncommon in SARD and coexist with other disease-specific autoantibodies. These findings highlight the complexity of interpreting anti-DFS70 antibodies and underscore the need for comprehensive serological testing and clinical correlation.