Serum SP1 and hCG beta-subunit (hCG beta) levels in choriocarcinoma, invasive mole, and hydatidiform mole--clinical significance of SP1/hCG beta ratio

Serum SP₁ (pregnancy-specific β₁, glycoprotein) levels in patients with choriocarcinoma, invasive mole, and hydatidiform mole were radioimmunoassayed and compared with simultaneously measured serum hCGβ-subunit (hCGβ) levels in order to evaluate the clinical significance of SP₁ determination. Serum SP₁ levels at the time of admission ranged from 6.4 to 1660 ng/ml in choriocarcinoma patients, 16.3 to 540 ng/ml in invasive mole, and 720 to 58,000 ng/ml in hydatidiform mole. $\text{SP}{}_1\text{hCGβ}$ ratios were under 1.0 in choriocarcinoma (0.3 ± 0.2, mean ± SD), over 1.0 in hydatidiform mole (10.9 ± 8.3), and intermediate in invasive mole (1.5 ± 0.3). In normal pregnancy, the ratio increases as pregnancy progresses, that is, from 15.25 in 7-week gestation to 14,090.90 in 40-week gestation. The mean $\text{SP}{}_1\text{hCGβ}$ ratio differs significantly among choriocarcinoma, invasive mole, and hydatidiform mole. $\text{SP}{}_1\text{hCGβ}$ ratio is likely to represent the degree of differentiation of trophoblastic cells. The $\text{SP}{}_1\text{hCGβ}$ ratio may be useful in differentiating between choriocarcinoma and invasive mole.