Learning curve for spotting ectopic pregnancy with ultrasound sparks debate

Debate continues in the medical community about how many exams it takes before a physician is proficient in identifying ectopic pregnancy with ultrasound. The American Institute of Ultrasound in Medicine recommends at least 300 sonographic examinations for obstetric indications. The American College of Emergency Physicians recommends a minimum of 25 exams in each emergency bedside sonography indication. A new study finds 25 exams are not enough, but 300 are probably too many.

In their prospective study, researchers at the Olive View Medical Center and University of California Los Angeles Medical Center assessed the learning curve of emergency physician training in emergency bedside sonography for first-trimester pregnancy complications. They found there is an appreciable learning curve that persists past 40 examinations (J Ultrasound Med 2010;29:1423-1428).

“Confirming the presence of an intrauterine pregnancy appears to be safely done by emergency physicians with appropriate training and a minimum number of exams, probably in the 25 to 40-exam range,” said Dr. Timothy Jang, lead author of the study and director of Emergency Ultrasound and an assistant professor of medicine at UCLA. “That, however, is different than excluding an ectopic pregnancy, which appears to require more experience, although probably a lot less than 200.”

A total of 670 patients underwent ultrasound for first-trimester pregnancy complications by one of 25 physicians who would go on to perform more than 25 examinations. Sensitivity and specificity for an intrauterine pregnancy were 80% and 86% for a physician’s first 10 examinations. Sensitivity and specificity of ultrasound for an intrauterine pregnancy were 100% and 100% for those performed after 40 examinations. The sensitivity and specificity of ultrasound for an ectopic pregnancy were 43% and 94% for a physician’s first 10 examinations. The sensitivity and specificity of ultrasound for an ectopic pregnancy was 75% and 89% for those performed after 40 examinations.

“I think the basic tenet of this study is the more experience you have, the better you become,” said Dr. David Bahner, the ultrasound director and an emergency medicine physician at Ohio State University in Columbus. “What this study is trying to address is there are multiple numbers as far as what is competency. How many exams does it take?”

At the outer edge of the spectrum, a study by Dr. Barbara Hertzberg, a radiology professor at Duke University, says competency requires more than 200 scans.

“This study adds to the literature and gets people thinking about the variables associated with the learning curve,” Bahner said. “This is not by any means definitive to say that 25 exams are too little, or 40 are too little. There’s a paucity of literature about the learning curve with ultrasound education.”

That there is a learning curve is not the problem because there is a learning curve to everything physicians do, Jang said. The point is to figure out what it is so physicians can be properly trained to ensure competence. And that’s where radiologists in particular come in.

“Radiologists can help by participating in the training of nonradiologists performing the exam rather than being fearful of them,” he said. “Washington University in St. Louis has developed a really good model for this. Dr. Jim Crane, a recognized leader in obstetric ultrasonography, helps to train the emergency physicians in obstetric ultrasound. That partnership allows for the best training of physicians and care for patients.”