Comparative Analysis of Line Immunoassay with Immunofluorescence Assay for the Identification of Autoantibodies in Patients with Suspected Systemic Autoimmune Disorders: A Cross-sectional Study

Abstract

Introduction: Systemic Autoimmune Diseases (SAD) are the diseases, including Rheumatoid Arthritis (RA), Systemic Lupus Erythematosus (SLE), sjogren’s syndrome, polymyositis, dermatomyositis, etc. where multiple organs are involved in the presence of a large variety of autoantibodies directed against one’s own immune system at various levels. They are one of the major causes of death and disability in all age groups and are characterized by the presence of Antinuclear Antibodies (ANA) in the blood of patients. Aim: To comparatively evaluate the utility of Line Immunoassay (LIA) with Indirect Immunofluorescence Assay (IIFA) for the detection and identification of ANA in suspected SAD patients. Materials and Methods: The present observational, crosssectional study was conducted on the collected samples of 560 clinically suspected SAD patients attending the Outpatient and Inpatient Departments (Medicine, Paediatrics, Orthopaedics, Dermatology and General Surgery) at Shri Ram Murti Smarak Institute of Medical Sciences, Bareilly, Uttar Pradesh, India (tertiary care hospital), from March 2016 to March 2020. Samples were subjected to ANA testing by IIFA and LIA. All variables anti-dsDNA, anti-Smd1, SSA/Ro and U1 SnRNP, SSA/ Ro, anti Proliferating Cell Nuclear Antigen (PCNA) and PO/RPP, SSB/La, anti CENP-B, Scl70, AMA-M2 and Mi-2 included in the study were presented in the form of percentages. Performance of LIA was reported in terms of sensitivity and specificity at 95% confidence interval. Data was analyzed using Statistical Package for the Social Sciences (SPSS) version 22.0 (Chicago, IL, USA) for windows. Results: Samples of both male (n=229) and female (n=331) patient of age group ranging from 0-90 years with mean age of 38.2 years were studied. Out of 560 samples, 197 (35.17%) patients were found to be ANA positive by IIFA. The LIA was positive in 175 (31.25%) patients. Of these 175 positive patients, 92 (52.57%) had a recognised autoimmune disease with the most common diagnosis was SLE, found in 38 (41.30%). In comparison to IIFA the sensitivity and specificity of LIA was found to be 82.13% and 98.62% respectively with 92.63% accuracy. Conclusion: The combined analysis of IIFA and LIA can be very useful for rapid identification of ANA which strengthen the initiation of treatment at the earliest to reduce disease morbidity and mortality.