Total human chorionic gonadotropin is a more suitable diagnostic marker of gestational trophoblastic diseases than the free β-subunit of human chorionic gonadotropin

Objectives: Human chorionic gonadotropin (hCG) levels are essential for the management of trophoblastic diseases. This study aimed to compare the sensitivities and relationships of two hCG measurement methods (total hCG and the free β-subunit of hCG) in managing gestational trophoblastic disease (GTD). Design and Methods: We analyzed data from patients treated for GTD at Chiba University Hospital between 2008 and 2019. We focused on cases where both total hCG (mIU/mL) and the free β-subunit of hCG (ng/mL) were measured on the same day. Results: Out of 80 patients (mean age 38.9 ± 11.7 years) and 158 measurements, 26 had values below the sensitivity threshold for both tests. Fifty-nine measurements were positive for total hCG but below the sensitivity threshold for the free β-subunit of hCG, whereas only two showed the opposite. Seventy-one measurements were positive for both total hCG and the free β-subunit of hCG. There was a significant correlation between total hCG and the free β-subunit of hCG with both positive values, (r = 0.94, p