Although clots in the lung (pulmonary embolism or PE) are the second-leading cause of sudden death in the United States, blood tests and ultrafast CT scanning to detect PE are being used on so many patients that over 90% of these tests are negative.
In a paper to be presented at the 2007 Society for Academic Emergency Medicine (SAEM) Annual Meeting, Jeff Kline, MD, Carolinas Medical Center, Charlotte, NC, will show that the use of simple clinical criteria can eliminate the risk and expense of these unnecessary tests.
The Pulmonary Embolism Rule-out Criteria, or the PERC rule, functions as a way to rule out clots in the lung. The blood test, called D-Dimer, has a very low specificity for PE, leading to many false positives. The CT scan costs $2500, has the potential for kidney damage in 1 in 12 patients, and has a heavy radiation dose that increases lifetime risk of cancer. Yet, doctors are ordering these tests for 2-3% of all Emergency Department patients or 3.5 million cases per year. According to the author, the fear of medical malpractice has led to a culture of doing tests rather than using the data available through clinical evaluation.
The study looked at an 8,138 patient random sample from 13 hospitals. By using a Web-based real-time data collection method and an extremely rigorous study design, it was able to capture the doctor's beliefs at the time of treatment, prior to the time that results were available. Importantly, the study design captured the physicians "gestalt" or gut instinct of how likely they thought PE was on their list. The results showed that fully two thirds of all testing is done in patients where the physician believed that the probability of PE was less than 15%.