Comparison of a novel chemiluminescence enzyme immunoassay (CLEIA) with enzyme-linked immunosorbent assay (ELISA) for the determination of MPO-ANCA in patients with ANCA-associated vasculitis

Background. Myeloperoxidase (MPO) anti-neutrophil cytoplasmic antibody (ANCA) represents the serological hallmark of ANCA-associated vasculitis (AAV). We evaluated the analytical and diagnostic accuracy of chemiluminescence enzyme immunoassay (CLEIA) versus enzyme-linked immunosorbent assay (ELISA) for the detection of MPO-ANCA. Methods. A total of 242 sera obtained from 51 patients with AAV and 103 patients without AAV were tested for MPO-ANCA by ELISA (NephroScholor MPOANC II) and CLEIA (the STACIA MEBLux test). Disease activity in the patients with AAV was determined based on the Birmingham Vasculitis Activity Score. We analyzed the correlations between the MPO-ANCA titers determined by the CLEIA and those determined by the ELISA, and also between the MPO-ANCA titers and the disease activity. Results. The MPO-ANCA titers determined by the CLEIA (x) were strongly correlated with those determined by the ELISA (y). The correlation could be expressed by the following equation in this study: y = 1.8x + 7.7 (r = 0.96; p < 0.0001). At the cutoff value of 3.5 U/ml, the CLEIA yielded positive test results for MPO-ANCA in 73 of the 242 sera (30.2%), while at the cutoff value of 20 U/ml, ELISA yielded positive test results in 57 of the 242 sera (23.6%). The CLEIA yielded false-positive test results in 4 of the 120 sera obtained from the non-AAV patients (3.3%), whereas the ELISA yielded a false-positive result in only 1 of the 120 sera obtained from the non-AAV patients (0.8%). The sensitivity and specificity of the CLEIA for the diagnosis of AAV were 100% and 96.7%, respectively, while those of the ELISA were 94.3% and 99.2%, respectively. The sensitivity and specifi city of the CLEIA for the prediction of active disease were 100% and 64.4%, respectively, while those of the ELISA were 94.3% and 73.6%, respectively. Conclusion. The false positivity rate of the CLEIA for MPO-ANCA tended to be high as compared with that of the ELISA. Also, according to the correlation coefficient between the results of the CLEIA and the ELISA calculated in this study, it is necessary to pay attention to the differences in the sensitivity and specifi city between CLEIA and ELISA.