Trophoblastic markers in the differential diagnosis of ectopic pregnancy

The serum levels of pregnancy-specific beta-1-glycoprotein (PSBG) and human chorionic gonadotropin (hCG) were measured by radioimmunoassay in 79 women admitted to the hospital because of uterine bleeding and pain in the lower abdomen. In 25 out of 26 patients (96%) with operatively confirmed ectopic pregnancy, hCG was found; PSBG was found in 22 out of 23 (96%). There was 1 patient in whom neither marker was found. In all of 14 patients with clinical signs of intrauterine pregnancy both hCG and PSBG were present. The levels of hCG and PSBG in patients with ectopic pregnancy (1558 +/- 465 mIU/ml and 739 +/- 386 ng/ml) or with inevitable abortion (1282 +/- 810 mIU/ml and 1511 +/- 658 ng/ml) were lower than those found in uncomplicated pregnancy of the same gestational length (20,100 +/- 2200 mIU/ml and 2821 +/- 673 microgram/ml), whereas in cases of threatened abortion ending in delivery, the levels were normal for the gestational time. Of 39 patients without clinical signs of pregnancy, hCG was detectable in the serum in 3 women and PSBG in 11 others. Seven of these 14 had an intrauterine contraceptive device (IUD) in situ, suggesting the possibility of a subclinical abortion. Our results show that the diagnosis of ectopic pregnancy can be improved significantly by the highly sensitive radioimmunologic measurement of serum hCG and/or PSBG concentrations, but these tests do not distinguish intrauterine from extrauterine sources of trophoblastic markers.