Efficient use of early obstetric sonography in the emergency department setting.

Objectives: Transvaginal sonography is frequently used in the emergency department (ED) to triage pregnancies of unknown location. The purpose of this study was to examine the utility of sonography in clinically stable patients with β-human chorionic gonadotropin (β-hCG) values below the discriminatory zone.

Methods: We conducted a retrospective cohort study of 408 consecutive ED patients who presented with pregnancies of unknown location and serum β-hCG levels between 5 and 2500 mIU/mL and underwent transvaginal sonography. Women were classified as receiving immediate treatment or expectant management. Predictors associated with immediate treatment were assessed by bivariate analyses and logistic regression.

Results: Of the cohort, 361 women (88.5%) received expectant management, and 6.9%, 3.1%, and 0% of patients with pregnancies of unknown location and β-hCG levels below 1000, 200, and 75 mIU/mL, respectively, received immediate treatment. Compared to the expectant management group, women receiving immediate treatment (n=47) were further from the last menstrual period (7.86 versus 6.10 weeks; P <.01), were more likely to report pain (59.6% versus 40.2% P = .01), had higher β-hCG levels(1183 versus 608 mIU/mL; P <.01), and had lower hematocrit levels (35.7% versus 37.0%; P < .01), with pain the most predictive factor for immediate treatment (odds ratio,5.97; 95% confidence interval, 2.45-14.53). A model combining symptoms, β-hCG, hematocrit, and weeks since the last menstrual period predicted the likelihood of sonography changing management from expectant management to immediate treatment with specificity of 98%.

Conclusions: The diagnostic utility of sonography in clinically stable patients presenting to the ED in very early pregnancy is limited. A model using symptoms, β-hCG, hematocrit, and the last menstrual period may aid clinicians to triage those who would benefit from immediate sonography.