Detection of desialylated forms of human chorionic gonadotropin

Urinary forms of human chorionic gonadotropin (hCG) with oligosaccharides deficient in sialic acid content (ashCG) have been reported to be excreted by patients with choriocarcinoma in greater amounts than by healthy, pregnant women. Although ashCG potentially could be a useful marker for the diagnosis and management of gestational trophoblastic neoplasia, the methods previously used for its detection were not suitable for routine clinical application. Therefore, we have devised a simpler method which can provide specific and sensitive measurements of ashCG in urine. This method, which is designated as a lectin-immunoradiometric assay (LIRMA), employs an agarose-coupled lectin to selectively extract the ashCG, which is then quantified directly with a purified and radiolabelled rabbit antibody. The LIRMA has been applied to demonstrate that there is an increased excretion of ashCG by choriocarcinoma patients. It is also applicable, in principle, for the study of any glycoprotein which has a reduced content of sialic acid in its carbohydrate side chains.