D-dimers and efficacy of clinical risk estimation algorithms: sensitivity in evaluation of acute pulmonary embolism

The goal of this study was to test the efficacy of clinical risk algorithms and a quantitative immunoturbidimetric D-dimer assay in the evaluation of patients undergoing pulmonary CT angiography for suspected acute pulmonary embolism.

From April 1, 2007, to March 31, 2008, emergency department evaluations for clinically suspected pulmonary embolism were performed with the revised Geneva score, a quantitative D-dimer assay, and pulmonary CT angiography.

Evaluations for pulmonary embolism were performed for 745 consecutively registered patients, 627 of whom were included in the study. The other 118 patients were excluded because a d-dimer assay was not performed. According to the revised Geneva score, 281 patients had low clinical probability of having pulmonary embolism; 330, intermediate probability; and 16, high probability. CT angiography showed that 28 patients had pulmonary embolism (six in the low-probability group, 17 in the intermediate-probability group, and five in the high-probability group). The sensitivity, negative predictive value, and specificity of the D-dimer assay were 100%, 100%, and 25% (low-clinical-probability group); 100%, 100%, and 33% (intermediate-probability group); and 80%, 80%, and 37% (high-probability group).

The data appear to support the use of a quantitative D-dimer assay as a first-line test in evaluation for pulmonary embolism when the clinical probability of the presence of pulmonary embolism is low or intermediate. The sensitivity and negative predictive value were 100% for these cases. More than 26% of CT angiographic examinations might have been avoided if the D-dimer assay had been used as a first-line test in the care of patients at low or intermediate risk. Because of the small sample size, the D-dimer assay is not recommended as a first-line test in the evaluation of patients at high risk.