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
AbstractAssay 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 β-hCG subunit (hCGβ) 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. hCGβ was determined by an automated fluorescence sandwich immunoassay (Kryptor-Free β hCG) and with a specific immunoradiometric assay (ELSA-F β 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. hCGβ assay and immunohistochemical staining revealed tumor cell secretion of hCGβ. In conclusion, a specific serum immunoassay for intact dimeric hCG without cross-reaction with hCGβ should be adopted as routine policy for pregnancy exclusion before liver transplantation.