Long-term Persistence of Opisthorchis viverrini Antigen in Urine: A Prospective Study in Northeast Thailand.
Worasith C., Wongphutorn P., Kopolrat KY., Homwong C., Techasen A., Thanan R., Wangboon C., Eamudomkarn C., Sithithaworn J., Crellen T., Sithithaworn P.
Antigen detected in urine for the diagnosis of opisthorchiasis has a low daily variation; however, the longer term variability in antigen concentrations is unknown. In this study, we prospectively monitored Opisthorchis viverrini antigen concentrations for 30 consecutive days and at subsequent monthly intervals in a cohort of opisthorchiasis-positive individuals. On the basis of the monoclonal antibody-based ELISA, the profiles of antigen-positive rate and antigen concentration exhibited no significant change over 30 days with a mean proportion positive of 87.1% (range 73.7%-100%), and the average antigen concentration was 29.7 ± 2.2 ng/mL (mean ± SE). The urine antigen concentration at baseline was similar to the subsequent measurements at 2, 4, 6, and 10 months in the follow-up study (P > 0.05). The consistency and low daily and long-term fluctuation of O. viverrini antigen in urine demonstrates the reliability of urine assay for diagnosis of opisthorchiasis.