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The American College of Physicians, in a paper published in the Annals of Internal Medicine, is recommending judicious use of the serum D-dimer test to evaluate patients with a suspected pulmonary embolism (PE). 

In general, ACP stresses that there’s no one-size-fits-all diagnostic approach, suggesting different strategies based on age and risk. “The use of computed tomography (CT) for the evaluation of patients with suspected pulmonary embolism is increasing despite no evidence that this increased use has led to improved patient outcomes, while exposing patients to unnecessary risks and expense,” said ACP President Wayne J. Riley, MD, in a statement issued by ACP. 

The recommendations are to help doctors eliminate unnecessary tests by identifying patients unlikely to have PE, as well as instances where plasma D-dimer testing and imaging are most appropriate, Riley indicated. A first step is to apply validated clinical prediction rules to determine pretest probability in patients suspected of having acute PE. “The benefit of such a decision tool is that it helps standardize the evaluation for physicians who infrequently encounter and/or evaluate patients for PE. The Wells and Geneva rules have been validated and are considered equally accurate in predicting the probability of PE,” ACP explained in its statement. 

For those patients who meet all rule-out criteria for PE and have a low pretest probability of this condition, ACP recommends against using D-dimer measurements or imaging studies. In the meantime, the high-sensitivity D-dimer test is a useful first diagnostic for patients who either have low pretest probability of PE but don’t meet all rule-out criteria, or have an intermediate pretest probability of PE. 

ACP prefers imaging with CT pulmonary angiography (CTPA) to the D-dimer as a more appropriate test for patients with high pretest probability of PE. To determine whether imaging is necessary among certain age groups, ACP recommends that for patients older than 50, doctors should use age-adjusted D-dimer thresholds—based on the patient’s age times 10 ng/mL—rather than a generic 500 ng/mL. ACP made this recommendation because normal D-dimer levels rise with age. Patients with a low or intermediate risk for PE with a D-dimer below the age-adjusted cutoff do not require imaging.

While highly sensitive, plasma D-dimer testing is nonspecific and false-positives can lead to unnecessary imaging, the use of an age-adjusted threshold resulted in maintenance of sensitivities with improved specificities in all age groups,” said Ali S. Raja, MD, a co-author of the paper and vice chair of Massachusetts General Hospital’s Department of Emergency Medicine, in ACP’s statement.