Value of D-dimers assay in diagnosis of pulmonary embolism

To determine the value of D-Dimers assay in the diagnosis of Pulmonary Embolism (PE) at Armed Forces Institute of Pathology, Rawalpindi, Pakistan from January to November 2000. Forty three consecutive patients clinically suspected of suffering from pulmonary embolism and referred to Armed Forces Institute of Pathology for Ventilation-Perfusion scan of lungs were inducted in the study. A detailed history was taken and clinical examination was performed. All patients were then subjected to Perfusion and/or Ventilation scan, which was taken as the standard for the diagnosis of PE. Blood samples were collected from all patients in trisodium citrate. Platelet poor plasma obtained from the samples was tested for D-Dimers semi-quantitatively using latex agglutination method. Out of 43 patients 14 (32.6%) had completely normal ventilation-perfusion scan hence the diagnosis of PE was excluded. In 6 (13.9%) patients the results were considered indeterminate. Abnormalities suggestive of pulmonary embolism were detected in 23 (53.5%) patients. D-Dimers were less than the cut off value of 500 ng/ml in 19 (44.2%) patients, whereas in 24 (55.8%) the levels were more than 500 ng/ml. When compared with the results of ventilation-perfusion scan the sensitivity of D-Dimers was 91.3% and specificity was 100%. Positive predictive value of the test was 100% whereas negative predictive value was 87.5%. D-Dimers assay combined with high clinical evidence is a cost effective, readily available test which can safely exclude the diagnosis of pulmonary embolism in majority of the cases.