Diagnosing ectopic pregnancy: decision analysis comparing six strategies.

OBJECTIVE: To compare six published methods of diagnosing ectopic pregnancy.

METHODS: Decision analysis compared six diagnostic algorithms involving combinations of clinical examination, transvaginal ultrasound, serum progesterone, serum hCG, and D&C. The population was composed of hemodynamically stable women who presented to a tertiary care university emergency department with abdominal pain or bleeding in their first trimesters. Outcome measures included number of missed ectopic pregnancies, potentially interrupted intrauterine pregnancies, surgical and diagnostic procedures, time until diagnosis, and cost.

RESULTS: Ultrasound followed by serum hCG in women with nondiagnostic scans yielded the most favorable outcomes; no ectopic pregnancy was missed, only 1% of all potential intrauterine pregnancies were interrupted, and time to diagnosis averaged 1.46 days. Quantitative hCG measurement followed by ultrasound only in women with hCG levels above the discriminatory zone was optimal if sensitivity of ultrasound to diagnose intrauterine pregnancy was less than 93%. Serum progesterone measurement was not favored because it was associated with missed ectopic pregnancies (2.6%).

CONCLUSION: Given the current accuracy of tests for diagnosing ectopic pregnancy, algorithms using a combination of ultrasound and hCG resulted in the best outcomes. Ultrasound as the first step was the most efficient and accurate method of diagnosing ectopic pregnancies.