Detection of antinuclear antibodies by indirect immunofluorescence method and its comparison with line immunoassay in a tertiary care hospital: A laboratory based observational study

Abstract

Antinuclear antibodies (ANA) are the hallmark of autoantibody production in autoimmune diseases and its testing is widely used as screening test in autoimmune diseases. ANA are directed against components of the cell nuclei such as DNA, histones, nucleoli and ribonucleoprotein. ANA are detected by indirect immunofluorescence (IIF) assay, which is among the most commonly used routine method for ANA detection as screening test, due to its ability to detect multiple antigens simultaneously. In this study, serum samples, referred to our laboratory for ANA testing were subjected for testing by IIF method and line immunoassay (LIA) during a study period of 20 months and the two were correlated with one another to establish any link between the two. A total of 279 serum samples were processed for ANA testing during the study period from June 2012 to January 2014. Of these 279 samples, 199(71.3%) were ANA IIF positive and 80(28.7%) were ANA IIF negative. The spectrum of various positive ANA IIF patterns are nucleus homogenous 52(26.1%), nucleus granular 50(25.1%), mixed pattern 57(28.6%), mitosis positive 15(7.5%), nucleus nucleolar 13(6.5%), nucleus dotted 8(4%), nuclear membrane 1(0.5%), cytoplasm positive 3(1.5%). All the samples tested by ANA IIF were subjected to LIA. Of these 159(56.9%) were both ANA IIF and LIA positive. In addition, 40(14.3%) samples were detected as IIF positive but LIA negative, whereas the rest 14(5%) samples were IIF negative but LIA positive. In the present study, a definite correlation was found in 201(71%) samples between ANA patterns and the LIA. Thus ANA IIF method using biochips can be used as a cost effective screening method for ANA testing and restricting LIA, which are expensive. This could economize on the cost of laboratory investigations in a developing country like India. Keywords: Antinuclear antibodies; Indirect immunofluorescence method; Immunoassay; Autoimmune diseases; Tertiary care hospital; Observational study