Triaging Women with Pregnancy of Unknown Location: Evaluation of Protocols Based on Single Serum Progesterone, Serum hCG Ratios, and Model M4.

Background: The purpose of the current study was to evaluate the ability of three protocols to triage women presenting with pregnancy of unknown location (PUL).

Methods: Women with pregnancy of unknown location were recruited from Aziz Medical Centre from 1st August, 2018 to 31st July, 2020. The criterion of progesterone, human chorionic gonadotrophin (hCG) ratio, and M4 algorithm were used to predict risk of adverse pregnancy outcomes and classify women. Finally, 3 groups were established including ectopic pregnancy, failed pregnancy of unknown location, and intrauterine pregnancy (IUP). The primary outcome was to assign women to ectopic pregnancy group using these protocols. The secondary outcome was to compare the sensitivity and specificity of the three protocols relative to the final outcome.

Results: Of the 288 women, 66 (22.9%) had ectopic pregnancy, 144 (50.0%) had intrauterine pregnancy, and 78 (27.1%) had failed pregnancy of unknown location. The criterion of progesterone had a sensitivity of 81.8%, specificity of 27%, negative predictive value (NPV) of 83.3%, and positive predictive value (PPV) of 25% for high risk result (ectopic pregnancy). The hCG ratio had sensitivity of 72%, specificity of 73%, NPV of 90%, and PPV of 44% for high risk result (ectopic pregnancy). However, model M4 had sensitivity of 86.4%, specificity of 91.9%, NPV of 95.8%, and PPV of 76% for high risk result.

Conclusion: Based on the findings of the study, it was revealed that prediction model of M4 had the highest sensitivity, specificity, negative predictive value and positive predictive value for high risk result (ectopic pregnancy).