Comparing the performance of urine and copro-antigen detection in evaluating Opisthorchis viverrini infection in communities with different transmission levels in Northeast Thailand.

To combat and eventually eliminate the transmission of the liver fluke Opisthorchis viverrini, an accurate and practical diagnostic test is required. A recently established urine antigen detection test using monoclonal antibody-based enzyme-linked-immunosorbent assay (mAb-ELISA) has shown promise due to its high diagnostic accuracy and the use of urine in place of fecal samples. To further test the utility of this urine assay, we performed a cross sectional study of 1,043 people in 3 opisthorchiasis endemic communities in northeast Thailand by applying urine antigen detection together with copro-antigen detection methods. The quantitative formalin-ethyl acetate concentration technique (FECT) was concurrently performed as a reference method. The prevalence of O. viverrini determined by urine antigen detection correlated well with that by copro-antigen detection and both methods showed 10-15% higher prevalence than FECT. Within the fecal negative cases by FECT, 29% and 43% were positive by urine and copro-antigen detection, respectively. The prevalence and intensity profiles determined by antigen detection and FECT showed similar patterns of increasing trends of infection with age. The concentration of antigen measured in urine showed a positive relationship with the concentration of copro-antigen, both of which were positively correlated with fecal egg counts. The data observed in this study indicate that urine antigen detection had high diagnostic accuracy and was in concordance with copro-antigen detection. Due to the ease and noninvasiveness of sample collection, the urine assay has high potential for clinical diagnosis as well as population screening in the program for the control and elimination of opisthorchiasis. Author summary Opisthorchiasis, caused by an infection with the liver fluke, Opisthorchis viverrini, is a neglected tropical disease endemic in Southeast Asia, particularly Thailand and Lao PDR. O. viverrini as well as Clonorchis sinensis have been classified as group I biological carcinogenic agents for cholangiocarcinoma (CCA). Due of the impact of control programs, the prevalence and worm burden in endemic communities have been reduced and this has caused the conventional fecal examination to be less sensitive and unreliable. In order to improve the diagnosis and to move towards the elimination of liver fluke to reduce CCA, we evaluated a novel urine antigen detection method by mAb-enzyme-linked immunosorbent assay for the diagnosis and screening of opisthorchiasis in endemic communities in northeast Thailand. We concurrently applied two coprological methods for antigen detection and fecal examination by formalin-ethyl acetate concentration technique, a reference method for comparison. Urine and copro-antigen detection had comparable diagnostic accuracy and both methods performed better than the fecal examination. Because of the ease and acceptance of urine specimen collection and handling, urine antigen detection has a high potential for the diagnosis and mass screening of opisthorchiasis in control and elimination programs.