Effective extraction and radioimmunoassay of chorionic gonadotropin in human urine

A single-step procedure for extracting and concentrating hCG from 24hr urine samples was developed. The procedure involves the adsorption chromatography with Vitachange (Permutit). Its hCG recovery was improved to be more than 90% compared with about 50% of a standard kaolin-acetone method. Nonspecific urinary protein concentration in extracts was also reduced. Thus, partial purification and concentration of urinary hCG by this procedure with subsequent RIA using antisera against the unique carboxyl-terminal peptide of hCG beta subunit provides a sensitive and specific method for detecting hCG in urine. In urine samples obtained from normal persons, the upper limit of hCG-immunoreactivity detected by this new system was 1.1 IU/24hr. However, 93% of subjects gave values lower than 0.5 IU/24hr. The urinary hCG level of lower than 1.1 IU/24hr may be designated as normal. This new assay system now provides reliable potentiality in the strict management of patients who are undergoing treatment for gestational trophoblastic neoplasia.