A Comparison of Spiral Computed Tomography and Latex Agglutination D-dimer Assay in Acute Pulmonary Embolism using Pulmonary Arteriography as Gold Standard

Abstract

Objective : To compare the diagnostic accuracy of contrast medium enhanced spiral computed tomography of the pulmonary arteries (s-CTPA) and a latex agglutination D-dimer assay in patients with suspected acute pulmonary embolism (PE) by using pulmonary arteriography (PA) and clinical follow-up as reference method. Design : Ninety hemodynamically stable patients with symptoms of acute pulmonary embolism were prospectively evaluated with s-CTPA and pulmonary arteriography (PA) within 24 h from admission. Plasma D-dimer levels on admittance were analyzed using a rapid latex agglutination D-dimer assay. The outcome of D-dimer concentrations in plasma below 0.25 and 0.5 mg/l was studied. Results : All PA and s-CTPA investigations were regarded as of acceptable diagnostic quality in a consensus reading. Thirty-three patients had a positive PA (37%). Three patients had false negative and two patients had false positive s-CTPA findings. s-CTPA had 91% sensitivity, 96% specificity, 94% positive predictive value (PPV) and 95% negative predictive value (NPV). The sensitivity and specificity for D-dimer below 0.5 mg/l were 79 and 88%, respectively. The PPV and NPV were 81 and 87%. If a cut-off level of 0.25 mg/l was used the corresponding figures were 91, 65, 63 and 92%. Conclusion : s-CTPA has a higher sensitivity and specificity than latex agglutination D-dimer. A cut-off level of 0.25 mg/l can be used as screening method, but s-CTPA must be performed to exclude false positive cases.