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Pregnancy-Specific β-l-Glycoprotein in Trophoblastic Disease^*

EEVA-MARJA RUTANEN and MARKKU SEPPÄLÄ

Department of Bacteriology and Immunology, University of Helsinki, and the Department of Obstetrics and Gynecology, University Central Hospital 00290 Helsinki 29, Finland

Address requests for reprints to: Dr. Markku Seppala, Academy of Finland, Department of Obstetrics and Gynecology, University Central Hospital, 00290 Helsinki 29, Finland.

To elucidate the potential significance of pregnancy-specific β-1-glycoprotein (PSBG) measurement in the monitoring of trophoblastic disease, we estimated the circulating PSBG levels by RIA in patients with choriocarcinoma (n = 17) and hydatidiform mole (n = 8). As controls, patients with rheumatoid arthritis, liver disease, infectious disease, and apparently healthy nonpregnant women were studied. Comparison was made between the occurrence of PSBG and hCG in patients with trophoblastic disease, and particular attention was paid to the frequency and magnitude of positive PSBGreadings in the hCG-negative samples from choriocarcinoma patients compared with those from the healthy controls and patients with nonneoplastic disease. PSBG immunoreactivity was found in 1 out of 20 patients with rheumatoid arthritis (3.7 µg/liter), 1 out of 20 patients with liver disease (4.8 µg/liter), and in none of the 29 patients with infectious disease. Four out of 85 apparently healthy nonpregnant women (4.7..) had serum levels up to 2.2 µg/liter immunoreactive PSBG. In choriocarcinoma patients, trophoblastic activity was assumed to be present by the demonstration of hCG in 129 of 367 serum samples obtained over a 2-yr period. The PSBG concentration was above the upper limit of normal (4.8 µg/liter) in 80 of these samples (62..). Immunoreactive PSBG (=4.8 µg/liter) was also demonstrated in 27 out of 238 hCG-negative serum samples (11..) from choriocarcinoma patients. After at least 3 months of remission, judged by the absence of demonstrable hCG, PSBG was observed in 11 out of 112 hCG-negative samples (10..). When 6 months had elapsed, PSBG was found in 9 out of 76 hCG-negative specimens (12..), and after 1 year of remission, PSBG was found in 7 out of 42 hCG-negative samples (17..). Peaks of PSBG and/or hCG were sometimes seen in asymptomatic patients, and they disappeared without treatment. In 35 serum samples from 9 choriocarcinoma patients, the hCG concentration was between 5–10 IU/liter, which lies near the assay sensitivity. Fifteen of these samples also showed an elevated level of PSBG (mean ± SEM, 31.3 ± 8.4 µg/liter), supporting the assumption that low hCG value reflected trophoblastic activity. We conclude that elevations of serum PSBG concentrations may occur in the absence of elevated hCG levels. The clinical significance of these isolated PSBG peaks is not obvious, but the PSBG estimation may be useful in those cases where the hCG value is ambiguous.

^* This work was supported by the Finnish Cancer Society (E.-M.R.), and the Research Council for Medical Sciences, Academy of Finland (M.S.).

Present address: Department of Reproductive Physiology, The Medical College of St. Bartholomew's Hospital, 51–53 Bartholomew Close, London EC1A7BE, England.

Received January 15, 1979.