Giuliano Giusti, MD; Anna Coerezza, MD; Giulia Cernuschi, MD
Potential Conflicts of Interest: None disclosed.
Giusti G., Coerezza A., Cernuschi G.; Clinical Decision Rules for Excluding Pulmonary Embolism. Ann Intern Med. 2012;156:168-169. doi: 10.7326/0003-4819-156-2-201201170-00024
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Published: Ann Intern Med. 2012;156(2):168-169.
TO THE EDITOR:
We read with great interest the article by Lucassen and colleagues (1) on clinical decision rules for excluding pulmonary embolism (PE). The authors concluded that clinical prediction rules and clinical judgment can safely exclude PE only when combined with d-dimer testing. The posttest probability that was considered safe to rule out PE was set at 2%, and the maximum upper confidence limit was 2.7% (1). We wonder whether this conclusion can be routinely applied to clinical practice.
In most of the cited studies on PE diagnosis, negative clinical follow-up at 3 to 6 months or positive findings on imaging—particularly computed tomography (CT)—are used as reference standards for excluding or confirming PE. Although this strategy allows for derivation of test sensitivity, it is less useful to evaluate their specificity (that is, false-positive rate). To this regard, Stein and coworkers (2) reported that 42% of patients at a low clinical risk score with positive CT results for PE can be considered as having false-positive results. Moreover, segmental and subsegmental PE occur more frequently in non–high-risk patients (3), and some authors have questioned the need for anticoagulant therapy in these patients, as they show a better prognosis (4). Thus, inferring from the cited literature that a posttest probability of PE (taking into account a low-scale risk score or clinical judgment) may vary between 4% and 9%, about 40% of these patients could be considered as having false-positive results. The mortality rate of these patients is about 15% (5), and we could speculate that patients at low-risk for PE by clinical risk score or clinical judgment, without assessing d-dimer, could have a mortality rate between 0.36 and 1%, thus corresponding to the mortality rate reported for patients treated with anticoagulants (4).
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