The use of D-dimer tests to exclude venous thromboembolism is an important advance in clinical practice and also has economic benefits. Ideally the test should be objective and a test that could be run on the routine coagulometer would obviate the need for additional investment in alternative hardware. A new automated latex particle immunoassay (MDA D-dimer) that can be run on a routine coagulometer was compared with a well established enzyme linked fluorescent assay (VIDAS D-dimer) on the basis of their ability to exclude venous thromboembolism. The assays were compared in 49 patients presenting to the emergency department with clinically suspected deep vein thrombosis or pulmonary embolism. After objective diagnostic imaging, 20 patients were confirmed to have venous thromboembolism. There was strong agreement between the assays in individual patients. Using a cut-off of 500 micrograms/l, both tests had a sensitivity of 100% and therefore a negative predictive value of 100%, however the MDA test would have spared more patients (20% vs. 12%) from further testing if a negative D-dimer was used to rule-out the diagnosis. It was concluded that a rapid, objective latex D-dimer test run on a routine coagulometer (MDA D-dimer) can be used to exclude the diagnosis of venous thromboembolism.
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