Predictive value of a rapid semiquantitative D-dimer assay in critically ill patients with suspected venous thromboembolic disease

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Abstract
To evaluate the performance of a new, rapid semiquantitative assay for the detection of circulating D-dimer in whole blood from critically ill patients with suspected venous thromboembolic disease. Prospective, blinded, single-center study. Medical intensive care unit (ICU) of Barnes-Jewish Hospital, St. Louis, MO, a university-affiliated urban teaching hospital. Two hundred thirty-nine adult patients with clinical suspicion of venous thromboembolic disease admitted to a medical ICU. Collection of blood samples within 24 hrs of clinical suspicion of venous thromboembolic disease. The main outcome measures evaluated included the occurrence of venous thromboembolic disease (i.e., lower extremity venous thrombosis, pulmonary embolism, catheter-associated venous thrombosis) and hospital mortality. Fifty-seven patients (23.8%) were classified as having venous thromboembolic disease during their ICU stays (pulmonary embolism, 21 patients; lower extremity thrombosis, 44 patients; line-associated venous thrombosis, 3 patients). The semiquantitative whole-blood assay for circulating D-dimer had a 96.4% sensitivity and a negative predictive value of 92.1% for identifying patients with venous thromboembolic disease. The specificity of this assay was 19.7%, and its positive predictive value was 26.9%. There was a strong correlation between the semiquantitative assay for circulating D-dimer and the quantitative measurement of circulating D-dimer using an enzyme immunoassay (Spearman's correlation coefficient, 0.8643; p < .001). We also identified a strong correlation between both the quantitative and semiquantitative measurements of circulating D-dimer with the sepsis classification proposed by the American College of Chest Physicians/Society of Critical Care Medicine (i.e., systemic inflammatory response syndrome, sepsis, severe sepsis, septic shock) for patients without venous thromboembolic disease (n = 182; quantitative measure: Spearman's correlation coefficient, 0.207; p = .002; semiquantitative measure: Spearman's correlation coefficient, 0.3519; p < .001). These preliminary findings suggest that a rapid whole-blood assay for the semiquantitative detection of circulating D-dimer may be a useful diagnostic tool for the exclusion of venous thromboembolic disease among critically ill patients.