Antinuclear Antibody Prevalence and Pattern Distribution: Insights from a Tertiary Care Center in India

Background: Antinuclear antibodies (ANAs) are established biomarkers for autoimmune diseases and are increasingly recognized for their relevance in malignancies. However, data on ANA patterns and their clinical significance in the Indian population remain limited. Objective: To determine the prevalence and pattern distribution of ANA and to evaluate their clinical associations in patients tested at a tertiary care center in India. Methods: This retrospective cross-sectional study analyzed 1,430 patients who underwent ANA testing by indirect immunofluorescence (IIF) on HEp-2 cells from January to December 2024. ANA patterns were classified according to International Consensus on ANA Patterns (ICAP) standards. Demographic and clinical data, including age, sex, referring department, and diagnoses (such as SLE, rheumatoid arthritis, malignancies, and chronic liver disease), were extracted from records. Statistical analysis was performed using SPSS version 26.0. Continuous variables were expressed as Mean ± SD. Categorical variables were presented as N (%) and analyzed using Chi-square or Fisher's exact test. Relevant test statistics (χ²) were reported where applicable, with significance set at p<0.05. Result: ANA positivity was 474/1,430 (33.1%). Among the 870 females, 374 (43.0%) were positive, while 100/560 males (17.8%) were positive (χ²=7.03, p=0.03). Systemic lupus erythematosus (SLE) showed the highest ANA positivity (92%), followed by rheumatoid arthritis (78%) and malignancies (31%). The most common ANA patterns were speckled (37.1%), homogeneous (29.4%), and nucleolar (13.3%). Rare patterns, such as mitotic spindle (0.6%) and rods/rings (0.4%), were mainly detected in patients with chronic liver disease and malignancies. Chronic lymphocytic leukemia (45%) and breast cancer (38%) exhibited the highest ANA positivity among malignancy subtypes. Conclusion: ANA testing remains essential for diagnosing autoimmune diseases and may have diagnostic value in malignancies. The detection of rare ANA patterns could help identify immune dysregulation in hepatic and oncologic conditions. Larger multicenter studies are needed to validate these findings and refine diagnostic strategies in oncology and autoimmunity.