NEW YORK (Reuters Health) – By evaluating risk factors for thromboembolism, physicians can reduce the number of computed tomography (CT) angiograms they order for patients with suspected pulmonary embolism (PE), investigators report.
“There’s virtually universal concern among radiologists that there has been overutilization of CT angiography,” Dr. Eric vanSonnenberg explained to Reuters Health.
“If a patient has symptoms and/or signs of PE and any risk factors then it’s reasonable” to have patients undergo CT angiography, he added. “On the other hand, if there are no risk factors, then the likelihood of PE is very low, and if the D-dimer test is negative, then chances are miniscule that the angiogram would be positive.”
Although CT angiography is considered the “modality of choice” for diagnosing PEs, its rapidly increasing use has sparked concern over the associated cost — which the researchers put at about $2000 to $3000 per exam — as well as the detrimental effects of radiation and the risk of contrast medium exposure.
As reported in a Radiology paper issued June 15 online, Dr. vanSonnenberg, from Arizona State University, Tempe, and his colleagues devised a simple scoring system based on known risk factors for venous thromboembolism. They verified its accuracy by reviewing medical records of 2003 patients who underwent CT angiography for possible PE between 2004 and 2006. D-dimer test results were available for 99 patients.
Risk factors were immobilization, malignancy, hypercoagulable state, excess estrogen state (pregnancy or peripartum state, oral contraceptive use, or hormone replacement therapy), a history of venous thromboembolism, age over 64 years, and male gender.
CT angiograms were positive for PE in 197 (9.84%) of patients. Of these, 192 had one or more risk factors. Among the 1806 with negative angiograms, 520 had no risk factors.
The authors estimate that the sensitivity of risk factor assessment was 96.46%, and the negative predictive value was 99.05%. The sensitivity and negative predictive values of the D-dimer test were both 100%.
Other researchers have suggested using a lower radiation imaging method, such as ventilation/perfusion (V/Q) scanning, in lieu of CT angiography. (See Reuters Health report, May 14, 2010.)
However, Dr. vanSonnenberg said, “That was a primary test some years ago, but CT angiography has supplanted that.”