D-dimer and D-dimer/fibrinogen ratio in predicting pulmonary embolism in patients evaluated in a hospital emergency department.

Objectives: The D-dimer level, fibrinogen level, and D-dimer/fibrinogen ratio are used in the diagnosis of pulmonary embolism, but results vary. We evaluated these parameters in the diagnosis of pulmonary embolism in emergency clinic patients.

Methods: In this prospective study, 200 patients (pulmonary embolism, 100 patients; no pulmonary embolism, 100 patients) had D-dimer and fibrinogen levels measured before intervention. Pulmonary embolism was diagnosed with computed tomography angiography or ventilation-perfusion scintigraphy.

Results: Compared with patients who did not have pulmonary embolism, patients who had pulmonary embolism had significantly greater mean D-dimer level (pulmonary embolism, 6±7 μg/ml; no pulmonary embolism, 1±1 μg/ml; P⩽0·001) and D-dimer/fibrinogen ratio (pulmonary embolism, 3±3; no pulmonary embolism, 0·4±0·4; P⩽0·001), but similar mean fibrinogen levels (pulmonary embolism, 337±184 mg/dl; no pulmonary embolism, 384±200 mg/dl; not significant). In patients who had pulmonary embolism, mean D-dimer level and D-dimer/fibrinogen ratio were greater in high-risk than non-high-risk patients. With D-dimer cutoff 0·35 μg/ml, sensitivity was high (100%) and specificity was low (27%) for pulmonary embolism. With D-dimer/fibrinogen ratio cutoff 0·13, sensitivity was high (100%) and specificity was low (37%) for pulmonary embolism.

Conclusion: A D-dimer level <0·35 μg/ml may exclude the diagnosis of pulmonary embolism. At a D-dimer cutoff 0·5 μg/ml and D-dimer/fibrinogen ratio cutoff 1·0, the D-dimer/fibrinogen ratio may have better specificity than D-dimer level in the diagnosis of pulmonary embolism, but the D-dimer/fibrinogen ratio may lack sufficient specificity in screening.