Beta-hCG vs intact hCG assays in the detection of trophoblastic disease.

We describe a case of choriocarcinoma in which increased concentrations of beta-choriogonadotropin subunits in serum indicated recurrence of metastasis long before the tumor could be confirmed by visualization techniques, while intact choriogonadotropin remained normal (less than 5 int. units/L). Therefore, detection or monitoring of choriocarcinoma requires the assay of free beta-hCG subunit or an assay that measures both the free beta-subunit and intact choriogonadotropin.