Clinical Usefulness of D-Dimer Depending on Clinical Probability and Cutoff Value in Outpatients With Suspected Pulmonary Embolism

Abstract

Modern management of suspected pulmonary embolism (PE) is mostly noninvasive and rests on clinical probability assessment, plasma D-dimer measurement, venous compression ultrasonography of the lower limbs, ventilation-perfusion lung scan,^1-3 and, recently, helical computed tomographic (CT) scan.^4,5 Clinical probability assessment is an essential step in contemporary diagnostic strategies that allows limiting the requirement for diagnostic tests.^1,6 For example, the association of a low clinical probability with normal findings on D-dimer enzyme-linked immunosorbent assay (ELISA) may safely rule out PE, without using imaging modalities.⁷ Clinical probability can be evaluated implicitly or explicitly by prediction rules.⁸ In the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study,⁹ clinical probability was assessed implicitly, and the prevalence of PE in the low, intermediate, and high clinical probability categories was 9%, 30%, and 68%, respectively. Other large-scale studies^4,10 confirmed the accuracy of implicit evaluation. The main limitation of implicit evaluation is its lack of standardization. Therefore, attempts have been made to standardize and render explicit the evaluation of clinical probability using scores or clinical prediction rules.¹¹ The 2 most widely validated rules are the Wells score¹² and the Geneva score.¹³ Both scores have been shown to have the same accuracy as that of implicit assessment.¹⁴