Transvaginal ultrasound in patients with low beta-human chorionic gonadotropin values: How often is the study diagnostic?

Study objective: To determine how often pelvic ultrasonography diagnoses or excludes ectopic pregnancy (EP) in patients who present with abdominal pain or vaginal bleeding and a beta-human chorionic gonadotropin (beta-hCG) level lower than 1,000 mIU/mL. Methods: This was a retrospective chart review of all patients who presented to the ED of an urban teaching hospital from August 1991 through July 1995 with lower abdominal pain or bleeding, a positive beta-hCG assay, and a quantitative beta-hCG value lower than 1,000 mIU/mL in whom pelvic transvaginal ultrasound was performed within 24 hours of the ED visit. Ultrasound procedures were performed in the radiology department by ultrasound technicians under the direct supervision of an attending radiologist or resident in radiology. Patients were excluded if they had recently delivered or undergone dilatation and curettage, had had a previous ultrasound examination during this pregnancy, had decreasing beta-hCG values, or were lost to follow-up before a definitive diagnosis was made. Results: A total of 111 patients met the inclusion criteria; 19 patients (17%; 95% confidence interval [CI], 10% to 24%) had diagnostic ultrasound findings. Of these, 10 findings were diagnostic of intrauterine pregnancy and 9 for EP. The beta-hCG values for the patients with diagnostic examinations ranged from 47 to 995 mIU/mL. Twenty-three study patients ultimately received a diagnosis of EP; of these, 9 (39%; CI, 19% to 59%) had a diagnostic initial ultrasound study. Five of the nine had beta-hCG values lower than 500 mIU/mL. Conclusion: Approximately one third of women with EP who present with beta-hCG values lower than 1,000 mIU/mL were identified with an urgent transvaginal ultrasound examination performed by trained ultrasound technicians. Clinicians should consider the use of pelvic ultrasound in patients with suspected EP, regardless of their beta-hCG values, particularly at institutions where ultrasound is readily available.