Introduction: Autoimmune disorders (ADs) affect 8.5% of the population globally. Diverse spectrums of antibodies are produced against nuclear antigens called antinuclear antibodies (ANA), which are detected by an array of laboratory tests such as enzyme-linked immunosorbent assay (ELISA), line immunoassay (LIA) and indirect immunofluorescence assay (IIFA). In this background, this study aimed to compare the diagnostic performance of LIA and IIFA in detecting and characterising ANA in patients presenting with clinical features suggestive of systemic autoimmune disease (SAD). Methods: A prospective cross-sectional diagnostic accuracy study was performed among 50 patients with clinically evident SADs, who were tested for ANA using IIFA (reference standard) and LIA. Results: The most common age group involved in this study was 20–40 years, with a female preponderance noted. ANA positivity was 48% by IIFA and 22% by LIA. The nuclear speckled pattern was the most frequent IIFA finding. Using IIFA as a reference, LIA showed 45.8% sensitivity, 100% specificity and moderate agreement with IIFA (κ = 0.468). All LIA-positive samples were also IIFA-positive. Conclusion: IIFA can be used as a screening test, whereas LIA can be a confirmatory test in patients with positive IIFA tests and also indicated in patients with strong clinical suspicion of autoimmune disease but with negative IIFA tests. This algorithm is economical in countries such as India.
Salim et al. (Sun,) studied this question.