Rate of Change of Serial β–Human Chorionic Gonadotropin Values as a Predictor of Ectopic Pregnancy in Patients With Indeterminate Transvaginal Ultrasound Findings, ,

Study objective: To determine the predictive value of the rate of change of serial β–human chorionic gonadotropin (hCG) values in patients with symptoms suggestive of ectopic pregnancy but who have indeterminate transvaginal ultrasound findings, and to determine whether the predictive value was enhanced depending on whether the endometrial cavity was empty at ultrasound examination. Methods: A retrospective study was performed on consecutive emergency department patients from August 1, 1991, through August 1, 1998, presenting with abdominal pain or vaginal bleeding, a positive β-hCG test result, and indeterminate transvaginal ultrasound findings. Patients were eligible for the study if they had a second β-hCG assay performed within 7 days of the initial visit and before either a diagnostic dilation and evacuation or laparoscopy. Patients were excluded if they were lost to follow-up. Patients were divided into 4 groups based on the rate of change of β-hCG values over a 48-hour interval (increase by >66%, increase by <66%, decrease by <50%, decrease by >50%). In addition, the 4 main groups were further subdivided depending on whether the endometrial cavity was empty at ultrasound examination. Intergroup differences in the frequency of ectopic pregnancy based on the rate of change of the β-hCG value were compared using logistic regression. Logistic regression also was used to determine whether addition of the ultrasound result improved predicative accuracy. A P value of less than .05 was considered significant. Odds ratios (ORs) were determined for each subgroup. Results: Three hundred thirty-one eligible patients were identified; of these, 24 were excluded. Of the 307 enrolled patients, 33 (10.7%) had a final diagnosis of ectopic pregnancy. Intergroup differences in the frequency of ectopic pregnancy based on the β-hCG rate of change were significant (P <.0001). Addition of the ultrasound result to this model further improved predicative accuracy (P <.0001). Overall, patients with increasing β-hCG values were at increased risk compared with those with decreasing β-hCG values, and patients with empty uteri at ultrasound were at increased risk compared with those with uteri that were not empty. Combining the β-hCG rate of change with the ultrasound result identified 3 high-risk groups: patients with β-hCG values that increased by less than 66% and an empty uterus at ultrasound (OR 24.8); patients with β-hCG values that decreased by less than 50% and an empty uterus at ultrasound (OR 3.7); and patients with β-hCG values that increased by more than 66% and an empty uterus at ultrasound (OR 2.6). Patients with β-hCG values that decreased by more than 50% were found to be at low risk for ectopic pregnancy irrespective of the specific endometrial findings at ultrasound. Conclusion: The rate of change of serial β-hCG values, in patients with an indeterminate pelvic ultrasound examination, is predictive of ectopic pregnancy. Addition of whether the endometrial cavity is empty at ultrasound leads to a further improvement in predictive accuracy. [Dart RG, Mitterando J, Dart LM: Rate of change of serial β–human chorionic gonadotropin values as a predictor of ectopic pregnancy in patients with indeterminate transvaginal ultrasound findings. Ann Emerg Med December 1999;34:703-710.]