Predictive value analysis of measurements of human chorionic gonadotropin, pregnancy specific beta 1-glycoprotein, placental lactogen, and cystine aminopeptidase for the diagnosis of ectopic pregnancy.

The diagnostic utility of serum and urinary human chorionic gonadotropin (hCG) measurements and serum measurements of pregnancy-specific beta 1-glycoprotein (PSBG), placental lactogen, and cystine aminopeptidase (CAP) was prospectively studied in 51 consecutive patients with suspected ectopic pregnancy who underwent laparoscopy or laparotomy. CAP was not detected in the sera of any patient with ectopic pregnancy. False-positive results in each assay were found in patients with intrauterine pregnancy or missed abortion. The overall efficiency of the tests were: urine hCG slide test, 47%; urine hCG tube test, 80%; serum hCG, 86%; serum PSBG, 82%; and human placental lactogen, 60%. Although measurement of serum hCG by radioimmunoassay is the most accurate biochemical test in predicting the correct diagnosis in patients with suspected ectopic pregnancy, the relatively high efficiency of the urinary hCG tube test, coupled with its ease of performance, low cost, and rapid turnaround time, makes it the most practical screening test.