A diagnostic strategy involving a quantitative latex d-dimer assay reliably excludes deep venous thrombosis

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Bates SM, Kearon C, Crowther M, et al(McMaster University, Hamilton, Ontario, Canada)BackgroundClinical diagnosis of deep venous thrombosis (DVT) can be inaccurate. Thus, objective testing is usually considered mandatory in patients with suspected DVT. Whether a negative finding on a quantitative latex d-dimer assay precludes further testing in patients with a low or moderate pretest probability of DVT was determined.MethodsFive hundred fifty-six consecutive outpatients with suspected first DVT seen at 3 Canadian hospitals were enrolled in the prospective study. Before d-dimer testing, patients were classified as having low, moderate, or high pretest probability of DVT. Those with low or moderate pretest probability and a negative d-dimer result did not receive further testing or anticoagulant treatment. All other patients underwent serial compression ultrasonography. Patients who did not receive a diagnosis of DVT were followed up for symptomatic venous thromboembolism.FindingsFifty-one percent of the patients had low or moderate pretest probability and a negative d-dimer test. One of these patients subsequently received a diagnosis of DVT. Overall, the negative likelihood ratio of the d-dimer test was 0.03.ConclusionsA negative finding on a quantitative latex d-dimer assay precludes additional evaluation in patients with a low or moderate pretest probability of DVT. Patients with an abnormal finding on d-dimer testing can be managed safely with serial compression ultrasonography.CommentWith the use of a latex immunoassay technique, the authors of this prospective study confirm the usefulness of d-dimer assays to exclude DVT. The latex technique appears to have a higher sensitivity than the whole-blood agglutination assay, a key parameter of a test used to exclude disease. Although bedside risk stratification is the critical starting point for determination of the likelihood of this entity, there may be some situations where the added reassurance of a negative d-dimer result may be helpful. The authors offer a model for bedside risk assessment adapted from Wells et al.1Wells PS Hirsh J Anderson DR et al.Value of assessment of pretest probability of deep-vein thrombosis in clinical management.Lancet. 1997; 350: 1795-1798Abstract Full Text Full Text PDF PubMed Scopus (977) Google Scholar Bates SM, Kearon C, Crowther M, et al (McMaster University, Hamilton, Ontario, Canada) BackgroundClinical diagnosis of deep venous thrombosis (DVT) can be inaccurate. Thus, objective testing is usually considered mandatory in patients with suspected DVT. Whether a negative finding on a quantitative latex d-dimer assay precludes further testing in patients with a low or moderate pretest probability of DVT was determined. Clinical diagnosis of deep venous thrombosis (DVT) can be inaccurate. Thus, objective testing is usually considered mandatory in patients with suspected DVT. Whether a negative finding on a quantitative latex d-dimer assay precludes further testing in patients with a low or moderate pretest probability of DVT was determined. MethodsFive hundred fifty-six consecutive outpatients with suspected first DVT seen at 3 Canadian hospitals were enrolled in the prospective study. Before d-dimer testing, patients were classified as having low, moderate, or high pretest probability of DVT. Those with low or moderate pretest probability and a negative d-dimer result did not receive further testing or anticoagulant treatment. All other patients underwent serial compression ultrasonography. Patients who did not receive a diagnosis of DVT were followed up for symptomatic venous thromboembolism. Five hundred fifty-six consecutive outpatients with suspected first DVT seen at 3 Canadian hospitals were enrolled in the prospective study. Before d-dimer testing, patients were classified as having low, moderate, or high pretest probability of DVT. Those with low or moderate pretest probability and a negative d-dimer result did not receive further testing or anticoagulant treatment. All other patients underwent serial compression ultrasonography. Patients who did not receive a diagnosis of DVT were followed up for symptomatic venous thromboembolism. FindingsFifty-one percent of the patients had low or moderate pretest probability and a negative d-dimer test. One of these patients subsequently received a diagnosis of DVT. Overall, the negative likelihood ratio of the d-dimer test was 0.03. Fifty-one percent of the patients had low or moderate pretest probability and a negative d-dimer test. One of these patients subsequently received a diagnosis of DVT. Overall, the negative likelihood ratio of the d-dimer test was 0.03. ConclusionsA negative finding on a quantitative latex d-dimer assay precludes additional evaluation in patients with a low or moderate pretest probability of DVT. Patients with an abnormal finding on d-dimer testing can be managed safely with serial compression ultrasonography. A negative finding on a quantitative latex d-dimer assay precludes additional evaluation in patients with a low or moderate pretest probability of DVT. Patients with an abnormal finding on d-dimer testing can be managed safely with serial compression ultrasonography.