What is the optimal protocol for diagnosis of ectopic pregnancy?

BACKGROUND: Ectopic pregnancy is a major cause of morbidity and mortality in women of reproductive age, but uncertainty remains about the best strategy for early diagnosis.

POPULATION STUDIED: This study used a hypothetical cohort of 10,000 women with first trimester pregnancies (positive pregnancy test result) who presented to an inner-city emergency department with abdominal pain or bleeding. Patients with any evidence of intra-abdominal hemorrhage were excluded. Their assumed prevalences of ectopic, intrauterine, and nonviable pregnancies were 9.4%, 61.1%, and 29.9%, respectively, based on a weighted average of 3 studies from inner-city teaching hospitals. The availability of 24-hour endovaginal ultrasound and human chorionic gonadotropin (HCG) testing was assumed. The results derived from this population are likely to be similar to those seen by family physicians, but caution should be exercised in generalizing this information to settings such as office practices or rural emergency departments.

STUDY DESIGN AND VALIDITY: The decision analysis defined 6 diagnostic algorithms: (1) transvaginal ultrasound (US) followed by quantitative HCG; (2) quantitative HCG followed by US; (3) progesterone followed by US and quantitative HCG; (4) progesterone followed by quantitative HCG and US; (5) US followed by repeat US; and (6) clinical examination. In practice, ultrasound and HCG are often done simultaneously, but otherwise the descriptions are appropriate. Strategies involving transabdominal US, serial HCGs, and methotrexate were not included. It was assumed that dilatation and curettage (D&C) and laparoscopy were 100% diagnostic and that US does not mistake intrauterine pregnancy for ectopic pregnancy. One- and two-way sensitivity analysis of test characteristics were performed using values obtained from the literature; prevalence of disease and performance of clinical examination were not included in the analysis.The methodologic strength of this study was fair. This clinical question is well suited to decision analysis; the different options are described well; and the analysis addresses appropriate outcomes, including unnecessarily interrupted pregnancies. The major weakness is a lack of information about the literature search and sensitivity analysis that makes it difficult to assess whether the authors’ underlying assumptions are valid. In addition, the authors assume that the highest priority is to avoid missed ectopic pregnancies. Although this is reasonable, no effort was made to query the literature, other professionals, or patients about what their preferred priorities would be, especially when the large majority of ectopic pregnancies are being detected by most of the strategies.

OUTCOMES MEASURED: The primary outcome was the number of missed ectopic pregnancies per 10,000 women. Secondary outcomes included the number of interrupted intrauterine pregnancies; the number of D&Cs, laparoscopies, USs, blood collections, and admissions; the days until diagnosis; and the hospital charges.

RESULTS: No ectopic pregnancies were missed with strategies that involved only US and HCG. Of those 2 strategies, US as the first step led to the fewest interrupted intrauterine pregnancies (70 vs 122). The progesterone algorithms missed more women with ectopic pregnancies (24) and required more surgeries but had the fewest number of interrupted pregnancies (25 and 39). US followed by US missed no ectopic pregnancies and had the shortest time until diagnosis but had the highest hospital charges. Clinical examination alone missed all ectopic pregnancies (940). Sensitivity analysis confirmed that the strategy of HCG followed by US was the most favorable, provided the sensitivity of the US for diagnosing intrauterine pregnancy was above 93%.