Importance of the detection method for intact dimeric human chorionic gonadotropin without interference with the free human chorionic gonadotropin β subunit for pregnancy exclusion before liver transplantation in a woman with cholangiocarcinoma

Abstract

Assay of human chorionic gonadotropin (hCG) is mainly used for the detection and monitoring of pregnancy, and for the follow-up of trophoblastic tumors. The serum free beta-hCG subunit (hCGbeta) is also a tumor marker in many non-trophoblastic tumors, including gastrointestinal cancers. In this work, we compared the performance of several immunoassays for pregnancy exclusion before liver transplantation and in the follow-up of a woman with cholangiocarcinoma. Serum hCG was detected with the Abbott Testpack plus hCG-Combo and measured with four automated sandwich immunoassays: ADVIA-Centaur, ACS:180, AxSYM and Dimension. hCGbeta was determined by an automated fluorescence sandwich immunoassay (Kryptor-Free beta hCG) and with a specific immunoradiometric assay (ELSA-F beta hCG, Schering). The expression of hCG was also evaluated by immunohistochemistry on sections of intrahepatic cholangiocarcinoma cells and on peritoneal metastases. Before transplantation, discordant results were observed for pregnancy exclusion. Qualitative Testpack and Dimension tests detected no hCG-like immunoreactivity, whereas the ADVIA-Centaur, ACS:180 and AxSYM tests revealed positive levels. The same discrepancy was obtained in follow-up of the patient after liver transplantation. hCGbeta assay and immunohistochemical staining revealed tumor cell secretion of hCGbeta. In conclusion, a specific serum immunoassay for intact dimeric hCG without cross-reaction with hCGbeta should be adopted as routine policy for pregnancy exclusion before liver transplantation.