Transvaginal sonography for diagnosing ectopic pregnancy: positivity criteria and performance characteristics

Despite the widespread use of TVS for diagnosing EP and extensive literature on the subject, there is no consensus regarding the best positivity criterion for adnexal findings or the performance characteristics of TVS. We conducted a literature search to identify original studies presenting suitable data on the use of TVS for the diagnosis of EP. The data were combined to determine the sensitivity and specificity of four sonographic criteria for EP, listed in order from most to least stringent: Criterion A, living extrauterine pregnancy; criterion B, extrauterine gestational sac containing yolk sac or embryo; criterion C, empty "tubal ring" or extrauterine gestational sac containing yolk sac or embryo; and criterion D, any adnexal mass other than a simple cyst. Positive and negative predictive values were computed using Bayes' theorem. Ten studies involving a total of 2216 patients, 565 with EP and 1651 without EP, were included in our analysis. Based on the combined data from these studies, criteria A, B, and C all have high specificities (99.5-100%) and positive predictive values (97.8-100%) but low sensitivities (20.1-64.6%) and mediocre negative predictive values (78.5-89.1%). Criterion D, the most lax criterion, has the most uniformly excellent characteristics, with only slightly lower specificity (98.9%) and positive predictive value (96.3%) but considerably higher sensitivity (84.4%) and negative predictive value (94.8%). The performance characteristics of TVS criteria for EP, computed by pooling data from published studies, indicate that the appropriate TVS criterion to diagnose EP is any noncystic adnexal mass. These performance characteristics can be used as a basis for comparing TVS with other proposed diagnostic modalities for EP.