Comparison of immunofluorescence assay (IF) with ELISA in detection of antinuclear antibodies

Patients with autoimmune connective tissue diseases often have antibodies that are directed against multiple nuclear antigens called as antinuclear antibodies (ANA). Two testing methods i.e. ELISA and indirect immunofluorescence (IF) techniques are used to detect these antibodies. Though ELISA is a cheaper method, IF is a preferred method for detection of ANA. In our study we have compared these two techniques for their diagnostic performance. Both the testing methods were applied on 155 samples. Of these, 135 samples were from test group and 20 samples were controls (negative and positive controls). Of the 135 test samples, IF yield positive results in 25(18.51%) cases and was found negative in 110(81.49 %) cases. Positive results were found by ELISA in 20(14.81%) cases and negative in 115(85.19 %) cases. Samples showing positive results with both methods were 18(13.33%) and samples showing negative results with both methods were 108(80.0%). 07(5.18%) cases that gave negative results by ELISA were found to be positive by IF. 02(1.48%) samples that were found to be positive by ELISA were negative by IF. Sensitivity & specificity of ELISA was compared with IF and was found to be 90.0% and 93.9% respectively. From this study it can be concluded that for testing ANA, IF is better than ELISA.