Anti-ENA Antibodies, ANA Patterns, Anti-ds DNA results, and Clinical Diagnosis: A Laboratory and Clinical Audit.

Abstract Background: The diagnosis of autoimmune diseases (AID) is challenging, due to overlapping features with other non-immune disorders. Anti-nuclear antibodies (ANA) /anti-cellular antibodies are the sensitive screening tests but anti-double-stranded-deoxyribonucleic-acid-antibody (anti-ds-DNA), and anti-extractable nuclear antigens (anti-ENA) are specific for AIDs. We aimed to look at anti-ENA in our patients and correlated them with ANA patterns, anti-ds-DNA and clinical diagnosis for proper interpretation and better patient management cost-effectively. Methods: A retrospective data analysis of 654 patients was done (1 st -February-2019 to 31 st –July-2021) who were tested for anti-ENA at the Immunology Department of Indus Hospital and Health Network. ANA and anti-ds-DNA results and clinical diagnosis were also analyzed for anti-ENA-positive patients. The statistical analysis was performed using IBM SPSS 24.0, P < 0.05.was considered statistically significant. Results: Anti-ENA was positive for at least one autoantibody in 245 (38.2%). ANA was positive in 97% of these patients (P=0.000) with speckled and homogenous as most predominant ANA patterns (63% and 33% respectively). Anti-SSA was the most common anti-ENA (n=50%) followed by anti-histones (23%), anti-Sm/RNP (26%), anti-nucleosome (22%). Among ANA-negative patients, anti-SSA was most common (n=5). Anti-ds-DNA was found in 66% of SLE patients. 14% of patients did not have a confirmed diagnosis before anti-ENA testing. Conclusions: Anti-ENA, ANA, and anti-ds-DNA antibodies are essential for AID diagnosis. However, their testing repertoire should follow an algorithm comprising of clinical features, followed by ANA results with nuclear, mitotic, and cytoplasmic patterns, anti-ENA, and anti-ds-DNA for a more meaningful, and cost-effective diagnostic approach.