Correlation of enzyme-linked immunoassay with line immunoassay for the detection of antinuclear antibody in autoimmune diseases

Abstract

INTRODUCTION: For the diagnosis of autoimmune disorders, detection of antinuclear antibodies (ANAs) is a key step. Indirect immunofluorescence assays are regarded as a gold standard method. Enzyme-linked immunosorbent assay (ELISA) is easily automated and less technical skills are needed and so used for ANA screening. Further testing is done with line immunoassay (LIA) for specific diagnosis of autoimmune disease. However, there is a lack of data comparing ELISA with LIA for ANA detection in the Indian population. OBJECTIVE: The objective of this study is to find the correlation between ELISA and LIA for ANA detection. METHODOLOGY: Serum samples received for ANA screen were tested using commercial kits for ELISA and LIA according to manufacturer's instructions. RESULTS: Total of 108 samples were tested both by ELISA and LIA. The total numbers of samples positive by ELISA were 26 and positive by LIA were 54 of 108. Samples that were both ELISA and LIA positive were 22 and both ELISA and LIA negative were 50. There was a fair level of agreement between the two methods (kappa = 0.333) with 95% confidence interval of 0.259–0.699. There was no significant difference in the distribution of most of the antibody types detected by LIA among ELISA positive and negative groups. However, the correlation of antibody type U1-Sn ribonucleoprotein with ELISA was found to be statistically significant (P = 0.0319). CONCLUSION: Detection of ANA is an important screening test. This present study shows moderate correlation between ELISA and LIA and hence both methods can be used depending on the workload of laboratories for cost-effectiveness. ELISA may be the preferred method for high-throughput laboratories.

Keywords

• antinuclear antibody
• autoimmune disorders
• enzyme-linked immunosorbent assay
• line immunoassay