Validation of a clinical risk scoring system, based solely on clinical presentation, for the management of pregnancy of unknown location

Objective: To assess a scoring system to triage women with a pregnancy of unknown location.

Design: Validation of prediction rule.

Setting: Multicenter study.

Patient(s): Women with a pregnancy of unknown location.

Intervention(s): None.

Main outcome measure(s): Scores assigned to factors identified at clinical presentation, total score calculated to assess risk of ectopic pregnancy (EP) in women with a pregnancy of unknown location, and a proposed three-tiered clinical action plan.

Result(s): The cohort of 1,400 women (284 ectopic pregnancies, 759 miscarriages, and 357 intrauterine pregnancies) was more diverse than the original cohort used to develop the decision rule. The recommendations of the action plan were low risk, intermediate risk, and high risk; the recommendation based on the model score was compared with clinical diagnosis. A total of 29.4% intrauterine pregnancies were identified for less frequent follow-up observation, and 18.4% nonviable gestations were identified for more frequent follow-up observation (to rule out an ectopic pregnancy) compared with intermediate risk (i.e., monitor in current standard fashion). For a decision of possible less frequent monitoring, the specificity was 90.8% (89.0-92.6) with negative predictive value of 79.0% (76.7-81.3). For a decision of more intense follow-up observation, the specificity was 95.0% (92.7-97.2). Test characteristics using the scoring system were replicated in the diverse validation cohort.

Conclusion(s): A scoring system based on symptoms at presentation has value to stratify risk and influence the intensity of outpatient surveillance for women with pregnancy of unknown location but does not serve as a diagnostic tool.