Accuracy of first-trimester ultrasound in diagnosis of tubal ectopic pregnancy in the absence of an obvious extrauterine embryo: systematic review and meta-analysis.

ABSTRACT

OBJECTIVES: To determine the accuracy of ultrasound in the diagnosis of a tubal ectopic pregnancy in the absence of an obvious extrauterine embryo. METHODS: This was a systematic review conducted in accordance with the PRISMA statement and registered with PROSPERO. We searched MEDLINE, EMBASE and The Cochrane Library for relevant citations from database inception to July 2014. Studies were selected in a two-stage process and their data extracted by two reviewers. Accuracy measures were calculated for each ultrasound sign, i.e. empty uterus, pseudosac, adnexal mass and free fluid in the pouch of Douglas, alone and in various combinations. Individual study estimates were plotted in summary receiver-operating characteristics curves and forest plots for examination of heterogeneity. The quality of included studies was assessed. RESULTS: Thirty-one studies including 5858 women were selected from 19,959 citations. Following meta-analysis, an empty uterus on ultrasound was found to predict an ectopic pregnancy with a sensitivity of 81.1% (95% CI, 42.1-96.2%) and specificity of 79.5% (95% CI, 68.9-87.1%). The corresponding performance of the pseudosac, adnexal mass and free fluid were 5.5% (95% CI, 3.3-9.0%) and 94.2% (95% CI, 75.9-98.8%); 63.5% (95% CI, 48.5-76.3%) and 91.4% (95% CI, 83.6-95.7%); and 47.2% (95% CI, 33.2-61.7%) and 92.3% (95% CI, 85.6-96.0%), respectively. CONCLUSION: Visualization of an empty uterus, adnexal mass, free fluid or a pseudosac has poor sensitivity for the diagnosis of a tubal pregnancy when an obvious extrauterine embryo is absent, but it has good specificity. We can therefore infer that ultrasound is more useful for 'ruling in' a tubal pregnancy than 'ruling out' one. However, the findings were limited by the poor quality of some included studies and heterogeneity in the index test and reference standard.