Comparative study of ELISA and indirect immunofluorescence for the detection of anti-neutrophil cytoplasmic antibodies. Evaluation of the SCIMEDX/EURO Diagnostica ELISA assay in a clinical setting.

This study evaluates the performance of a commercial ELISA assay for detection of anti-neutrophil cytoplasmic antibodies (ANCA). Anti-proteinase 3 (anti-PR3) and anti-myeloperoxidase (anti-MPO) ELISA by (SCIMEDX/EURO Diagnostica, Denville, NJ) were compared with the indirect immunofluorescence (IIF) method using ethanol-fixed neutrophils. Three hundred sixty serum samples were examined. There was complete correlation of results in 357 (99.2%) cases between cANCA pattern and anti-PR3 results, and in 356 (98.9%) cases between pANCA pattern and anti-MPO ELISA results. The specificity of ELISA for detection of vasculitis was 95.7% and sensitivity was 60%, whereas for IIF, they were 95.7% and 65%, respectively. The ELISA showed good reproducibility with interassay variation (CV), ranging from 7.1% to 13.2%. Our results show that SCIMEDX/EURO Diagnostica ELISA for ANCA is a reliable and reproducible method that is as good as IIF for detection of ANCA.