Estimation of sensitivity and specificity of antinuclear antibody by automated indirect immunofluorescence and enzyme-linked immunoassay

Immunofluorescence and serology analysis are the most common laboratory methods for diagnosing antinuclear antibodies in autoimmune diseases and are paramount for screening and therapeutic purposes. This study aims to estimate the sensitivity and specificity of antinuclear antibodies measured by automated indirect immunofluorescence and enzyme-linked immunoassay in patients at risk for autoimmune diseases.

Serum antinuclear antibodies in 3020 patients suspected of autoimmune diseases at Nobel Medical Laboratory, Esfahan, IRAN, were measured from 2017 until 2020 with automated indirect immunofluorescence and enzyme-linked immune assay methods. The sensitivity, specificity, prevalence, positive and negative predictive value, and likelihood ratio were calculated for each technique. In addition, the receiver operating characteristic curve (ROC) was analysed as a statistical method for assessing the diagnostic accuracy of these tests.

The immunofluorescence method demonstrated low sensitivity and high specificity compared with the enzyme-linked immunoassay. For the automated indirect immunofluorescence method, sensitivity and specificity were 88% and 62%, respectively, whereas this number for the ELISA method was determined as 89.6% and 28.5 %, respectively.

It is crucial to choose a suitable method for detecting autoantibodies for diagnostic purposes. ANA analysis by a sensitive test, such as an enzyme-linked immunoassay, should be used for screening. In contrast, a highly specific test, such as an indirect immunofluorescence assay, should be used to confirm the result and monitor dynamic treatment.