Abstract
BACKGROUND: The preferred method of differentiating patients with ectopic pregnancy (EP) from those with pregnancy of unknown location (PUL) is still a clinical challenge. Currently, there is no worldwide consensus exists regarding the most effective biochemical diagnostic strategy for triaging these patients. OBJECTIVE: To improve early prediction of EP in patients with PUL by using a combination of the humanchoriogonadotropin (hCG) ratio and serum progesterone measured at the initial visit. STUDY DESIGN: This prospective multicenter cohort study included 1575 patients with PUL. The hCG ratio and progesterone were assessed to stratify the risk of EP. RESULTS: Final outcomes were available for 1509 (95.8%) patients; 168 EP (11.1%) including persistent PUL, 548 intrauterine pregnancies (36.3%), 786 failed PUL (52%), and 7(0.5%) molar pregnancy. The area under the curve for EP prediction using hCG ratio was 0.81. Sensitivity and negative predictive value (NPV) for hCG ratio alone were 0.85 and 0.97, respectively. Combining a hCG ratio >1.65 with progesterone >35 nmol/L improved sensitivity to 0.96 and NPV to 0.99. CONCLUSIONS: Combined measurement of hCG ratio and progesterone at the initial visit reliably rules out EP in real-world clinical practice.