Progesterone as a predictor of ectopic pregnancy when the ultrasound is indeterminate

The objective of this study was to evaluate a progesterone cutpoint of 5.0 ng/mL ability to identify abnormal pregnancy (abnormal intrauterine pregnancy and ectopic pregnancy) as well as ectopic pregnancy alone in 2 subclasses of indeterminate ultrasounds. This was a prospective observational study of emergency department patients with abdominal pain or vaginal bleeding and an indeterminate transvaginal ultrasound. Two subclasses of indeterminate ultrasounds were eligible: those with an empty uterus and a β-human chorionic gonadotropin value <3,000 mIU/mL and those with a nonspecific fluid collection. Patients were enrolled if a progesterone assay was collected the day of the emergency department visit. Patients were excluded if lost to follow-up. One hundred sixty patients were enrolled. Of these, 24 were diagnosed with ectopic pregnancy. The sensitivity and specificity of progesterone identifying abnormal pregnancy were 84% and 97%, respectively. The sensitivity and specificity of progesterone identifying ectopic pregnancy were 88% and 40%, respectively. In the 2 subclasses, the progesterone cutpoint was both sensitive and specific in identifying abnormal pregnancy and was sensitive but only moderately specific for identifying ectopic pregnancy.