Pregnancy-specific and pregnancy-associated proteins in threatened abortion.

Pregnancy sera (390) were taken between the 5th and 16th weeks of gestation, from subjects whose pregnancies were uneventful throughout the entire gestation period. In-house curves of first-trimester normal values (10th, 50th, 90th percentile) were established for human chorionic gonadotropin (hCG), human placental lactogen (hPL), pregnancy-specific beta 1-glycoprotein (SP-1), pregnancy-associated plasma protein A (PAPP-A), and pregnancy-associated alpha 2-glycoprotein (alpha 2-PAG) after the measurement of these proteins in the sera by immunoassay. Eighty sera from patients with threatened abortion were also obtained and the placental proteins mentioned above were determined. Values falling below the 10th percentile of the normal population were classified as positive (i.e., pathological) results; the others were considered negative. Based on the outcome of the pregnancy, the results were grouped into true positives (low value and lost pregnancy), false positives (low value and ongoing pregnancy), true negatives, and false negatives. The sensitivity, specificity, and the positive predictive value of each protein as an indicator for abortion were calculated. In terms of specificity hCG and SP-1 were good, whilst PAPP-A and hCG showed the highest sensitivity. The best predictive values were obtained from SP-1 and hCG. The results show that PAPP-A and SP-1 perform satisfactorily but that none of these proteins significantly improves on hCG.