Accuracy of ultrasound for ectopic pregnancy in the emergency department is not helped by measuring a key pregnancy hormone
Research Activities, April 2012
Measuring serum levels of beta-human chorionic gonadotropin (beta-hCG), a pregnancy-related hormone, is not helpful to bedside pelvic ultrasound imaging (ultrasonography) in diagnosing ectopic (outside-the-uterus) pregnancy among women who come into the emergency department (ED) with abdominal pain or vaginal bleeding, according to a new study. Ectopic pregnancy, observed in 2 percent of all pregnancies and up to 13 percent of pregnancies with symptoms, is a major cause of maternal illness or even death.
Traditionally, a beta-hCG discriminatory zone (a serum hormone level of 3,000 mIU/mL) has been used in combination with diagnostic ultrasonography in the radiology department to identify women likely to have an abnormal pregnancy, including embryonic demise and ectopic pregnancy. The researchers found that bedside pelvic ultrasonography, done by trained emergency physicians, had an overall sensitivity of 71 percent and specificity of 99 percent in detecting normal or abnormal intrauterine pregnancy. However, there was no level of b-hCG at which emergency physicians visualized an intrauterine pregnancy with certainty. Therefore, use of the beta-hCG discriminatory zone with indeterminate bedside ultrasound findings did not allow for the differentiation between intrauterine pregnancies and abnormal pregnancies.
The researchers found that the serum-hormone discriminatory zone had a specificity of 35 percent and specificity of 58 percent for patients with symptoms and an indeterminate bedside imaging result. Based on these findings, the researchers do not recommend using the traditional beta-hCG discriminatory zone, developed for use with more sensitive radiology ultrasound imaging, with bedside ultrasound imaging in the ED. The study was conducted with patients seen in the ED of a large, urban teaching hospital for possible ectopic pregnancy. The study was funded in part by the Agency for Healthcare Research and Quality (HS15569).
More details are in "Use of a beta-hCG discriminatory zone with bedside pelvic ultrasonography," by Ralph Wang, M.D., Teri A. Reynolds, M.D., Hugh H. West, M.D., and others in the July 2011 Annals of Emergency Medicine 58(1), pp. 12-20.