Comparative analysis of electro-chemiluminescence immunoassay, enzyme-linked immunosorbent assay and rapid immunochromatographic test for detection of hepatitis B surface antigen

Background: Electro-chemiluminescence immunoassay (ECLIA), enzyme-linked immunosorbent assay (ELISA), and rapid immunochromatographic test (RICT) are currently commonly used for the detection of hepatitis B surface antigen (HBsAg). Although a few studies have been performed to compare the efficiency of these three different serological assays, but there are still many grey areas where clear guidelines are required to give the reports as reactive or nonreactive. Materials and Methods: We compared three different methods of detecting HBsAg: RICT, ELISA and ECLIA. The aim of this cross-sectional study was to analyze the performance of these tests and evaluate the cut off index (COI) of ECLIA to be considered as positive. Some of the representative samples that showed a discrepancy between ELISA and ECLIA were confirmed by nucleic acid amplification test (NAAT). Results: A total of 3846 samples were included in the study, of which 259 (6.73%) were positive by ECLIA. Of these 259 samples, 68 were positive by both ECLIA and ELISA and had COI of >5 in ECLIA, whereas 191 were positive by ECLIA only (COI between 0.9 and 5). Hence, the concordance rates of the ECLIA and ELISA in detecting serum HBsAg was 26.25% while the same for ELISA and RICT was 31.57%. Four representative samples which were positive by ECLIA and ELISA (i.e., COI >5) were positive with NAAT. However, one sample which was negative by ELISA and positive by ECLIA (i.e., COI <5) was negative by NAAT. Cohen's K showed moderate agreement between ELISA and RICT and fair agreement between ELISA and ECLIA. Conclusions: ECLIA seems a promising and sensitive test to detect HBsAg, however, we suggest, samples with COI between 1 and 5 should be reported cautiously and preferably be combined with NAAT or any other molecular method before considering as positive.