Atsuko, Mikiya

Eri, Katayama

Natsuko, Nakamura

Asuka, Sato

Hideo, Matsui

Makio, Shozu

Kaori, Koga

Free β-subunit

Gestational trophoblastic disease

Choriocarcinoma

Hydatidiform mole

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.

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 < 0.001; Spearman's correlation test). Of the 85 measurements with undetectable free β-subunit levels, 26 also had undetectable total hCG levels. However, total hCG was detectable in 59 patients from these cases, with a median value (interquartile range) of 2.9 (1.75-4.9) mIU/mL.

In the management of GTD, the use of the free β-subunit system alone cannot be recommended.