Serum progesterone in the diagnosis of ectopic pregnancy: a valuable diagnostic test?

The value of a single serum progesterone (P) assay in the diagnostic work-up of suspected ectopic pregnancy was investigated in 89 patients with ectopic pregnancy and 27 patients with incomplete abortion. Reference values for P in the blood were obtained from 77 patients with normal intrauterine pregnancies in the first trimester. With the use of a discriminatory level of 63 nmol/l (20 ng/ml), sensitivity of 92%, specificity of 84%, positive predictive index of 90%, and negative predictive index of 87% were achieved. Addition of pelvic ultrasound further improved the diagnostic accuracy. It is concluded that serum P measurement offers a valuable adjunct to existing methods of diagnosis of ectopic pregnancy.