Abstract
INTRODUCTION: Antinuclear antibodies (ANA) are biomarkers used to diagnose, monitor, differentiate, and treat various systemic autoimmune rheumatic diseases (SARDs). The gold standard test for SARD screening involves using human epithelial cells (HEp-2) in an indirect immunofluorescence assay (IIFA) to detect ANA. However, diagnosing autoimmune disorders can be challenging when patients test ANA-negative but exhibit specific autoantibody patterns targeting the cytoplasm or mitotic spindle apparatus in the IIFA. To address this, the International Consensus on Antinuclear Antibody Patterns has proposed the term "anticellular antibodies" (ACA) to encompass various types of autoantibodies, including ANA. This study explores the rationale for shifting from reporting ANA to ACA in diagnosing SARDs. MATERIALS AND METHODS: An institutional observational study was conducted on 973 suspected and previously diagnosed patients in the Immunofluorescence Laboratory of the Department of Biochemistry of North Bengal Medical College and Hospital, West Bengal. IIFA using HEp-2 and monkey liver tissue (primate) substrates (EUROIMMUN, Lübeck, Germany) was performed after diluting patient serum samples at a ratio of 1:100. RESULTS: Among the 973 study participants, 585 (60%) tested positive for ACA. Of these ACA-positive cases, 140 (24%) showed anticytoplasmic antibody positivity. This included 38 (6.5%) cases with isolated anticytoplasmic antibody positivity and 102 (17.4%) cases positive for both antinuclear and anticytoplasmic antibody patterns. Isolated anticytoplasmic antibodies were more prevalent among females of reproductive age, accounting for 22 (58%) of such cases. CONCLUSIONS: The IIFA detected various autoantibodies when diagnosing SARDs. The presence of isolated anticytoplasmic antibodies in ANA-negative patients with autoimmune diseases indicates that the term ACA is more appropriate than ANA for diagnosing and reporting SARDs, as it may help reduce false-negative results.