The number of MDCT examinations for suspected pulmonary emboli (PE) is rapidly increasing amongst ER patients, with a decrease in the number of positive studies. This may be due to a failure to adhere to established clinical guidelines for evaluating patients with suspected PE, according to a study performed at the Warren Alpert Medical School of Brown University and Rhode Island Hospital, Providence, RI.
Current accepted clinical practice indicates that patients with a low clinical suspicion for PE should undergo D-dimer testing, then MDCT if positive. A total of 5,344 patients were reviewed. “42% of patients had a positive D-dimer exam and did not have a CT scan. Current protocols suggest that those patients should have had a scan,” said Michael T. Corwin, MD, lead author of the study. “MDCT was performed in 7% of patients with negative D-dimer results, and the same protocols suggest that those patients should not have undergone a scan,” said Dr. Corwin.
“Anytime a patient gets a CT scan there is a radiation dose. The evaluation of patients with suspected PE should include D-dimer and CT testing in a more standardized fashion so that we can save patients from having unnecessary CT scans. The D-dimer should only be used in patients with a relatively low suspicion of having PE. If the D-dimer test is positive, then patients should have the CT. If the test is negative then no scanning is needed,” he said.
“PE is very difficult to diagnose and there are a lot of factors you have to take into account. Most physicians are aware of D-dimer testing but whether or not they use it is often determined in a non-standardized fashion,” he said.
“MDCT is a great test. It’s fast, easy, accurate and provides physicians with tons of information. However we are ordering a lot of CT scans and what we’re finding is that a lot of these tests are negative. D-dimer testing does not rule out PE completely, but in patients with a low-probability of having it, based upon their presenting clinical picture, a negative D-dimer can spare them the radiation dose associated with MDCT,” said Dr. Corwin.
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