Emergency department diagnosis of ectopic pregnancy. STUDY OBJECTIVES: To assess the accuracy of the history and physical examination as compared to the addition of serum progesterone screening for ectopic pregnancy in women presenting to the emergency department. DESIGN: Prospective, consecutive case series, N = 2,157. SETTING: ED of the Regional Medical Center at Memphis, a publicly subsidized, 450-bed acute care hospital staffed by residents and faculty of the University of Tennessee, Memphis. TYPE OF PARTICIPANTS: All ED patients with a positive urine pregnancy test treated between January 1 and December 31, 1988. INTERVENTIONS: Screening history, physical examination, and serum progesterone (P) and quantitative human chorionic gonadotropin (hCG) titer. MEASUREMENTS: All discharged patients were given follow-up appointments within two weeks; those found to have a P less than 25 ng/mL were called to return for repeat hCG and transvaginal ultrasound. MAIN RESULTS: One hundred sixty-one of 2,157 patients (7.5%) with a positive urine pregnancy test were found to have an ectopic pregnancy. All but five had a P of less than 25 ng/mL (sensitivity, 97%); four of these were admitted for immediate surgery because of symptoms. Overall, the ED physician detected 89 of 161 ectopics (55.3%) on initial presentation, 53 (60%) of which were ruptured at the time of surgery. Seventy-two patients (44.7%) who were discharged but later found to have an ectopic pregnancy had benign clinical presentations, including 41 with vaginal bleeding. There were no statistically significant differences in the presenting symptoms of patients with unruptured ectopics compared with normal intrauterine pregnancies. All but one of the 72 discharged patients were noted the following day to have a progesterone of less than 25 ng/mL and contacted to return. Eight of these were found to have a ruptured ectopic at the time of surgery. Only 91 of 161 patients (56.5%) with ectopic pregnancy acknowledged one or more clinical risk factors on follow-up questioning. CONCLUSION: The standard history and physical examination, including those performed by gynecologic specialists, are insufficiently sensitive for early detection of unruptured ectopic pregnancy. EDs with a high incidence of ectopic pregnancy should strongly consider implementation of a universal progesterone screening program to decrease unnecessary patient morbidity and the risk of mortality from undiagnosed ectopic pregnancy. 