Clinical use of immunoperoxidase markers in excluding ectopic gestation

Ectopic pregnancy is suspected when a pregnancy test is positive and an Arias-Stella phenomenon with decidua is seen on endometrial curettings in the absence of chorionic villi and trophoblast. We performed immunoperoxidase stains for beta-hCG, hPL, placental alkaline phosphatase, and keratin (AE1/AE3) on endometrial curettings of 72 patients with first-trimester bleeding in whom ectopic pregnancy was suspected based on routine hematoxylin and eosin (H&E) stain. Negative immunoperoxidase stains correlated with a retrospective patient chart review identified only ten patients with extrauterine pregnancy, a prevalence of 14%. The sensitivity of hCG, hPL, placental alkaline phosphatase, and keratin markers in detecting trophoblastic cells in the curettings was 42, 48, 24, and 69%, respectively. Each marker had a specificity of 100%. When both keratin and hPL were used, the sensitivity improved to 73%; however, there was no advantage in using three or more markers. We conclude that 73% of patients suspected to have ectopic pregnancy would be spared additional diagnostic techniques when immunoperoxidase markers for keratin and hPL are used on endometrial curettings without trophoblast on routine H&E stain. The procedure requires only 3 hours of laboratory time.