EARLY DIAGNOSIS OF ECTOPIC PREGNANCY USING RECEIVER OPERATOR CHARACTERISTIC CURVES OF SERUM PROGESTERONE CONCENTRATIONS

The objective was to assess the usefulness of serum progesterone conce ntrations in the differentiation of intra-uterine (viable and non-viab le) and extra-uterine pregnancies. Progesterone concentrations were pr ospectively measured at 4, 5 and 6 weeks gestation in 338 pregnancies which resulted in 242 viable births, 81 abortions and 15 ectopic pregn ancies. Progesterone threshold analysis was performed using receiver-o perator characteristic curves. The progesterone threshold value for ec topic pregnancy at 4 weeks was 5 ng/ml, at 5 weeks 10 ng/ml and at 6 w eeks 20 ng/ml. A significant difference was observed between all intra -uterine versus ectopic pregnancies (P = 0.0005), but not between viab le versus non-viable intra-uterine pregnancies (P = 0.37). The differe nces were most clearly defined at 4 weeks and decreased with increasin g gestation. We conclude that serum progesterone and gestational age t aken together can differentiate intra-uterine from extra-uterine pregn ancies with a very high sensitivity and specificity at 4 weeks gestati on, a time when ectopic pregnancies are not evident on ultrasound exam ination.