D-dimer testing and impedance plethysmography were effective for the exclusion of deep venous thrombosis
ACP J Club. 1997 Nov-Dec;127:74. doi:10.7326/ACPJC-1997-127-3-074
Ginsberg JS, Kearon C, Douketis J, et al. The use of D-dimer testing and impedance plethysmographic examination in patients with clinical indications of deep vein thrombosis. Arch Intern Med. 1997 May 26;157:1077-81.
To determine whether normal D-dimer testing and impedance plethysmography (IPG) results can rule out the diagnosis of deep venous thrombosis (DVT).
A blinded comparison of D-dimer testing with IPG and compression ultrasonography to rule out DVT.
4 university hospitals in Canada.
401 patients (mean age 61 y, 65% women) who had had a first episode of suspected DVT.
Description of tests and diagnostic standard
An assessment of pretest probability was done for all patients. At the time of referral, the bedside D-dimer test was done by a research nurse or technologist. Test results were considered positive if any agglutination was seen. On the same day, IPG by using the occlusive cuff technique was done on all patients. Patients were assigned to 1 of the following 4 groups on the basis of their test results: group 1, both tests were normal; group 2, D-dimer test was normal and IPG was abnormal; group 3, D-dimer test was abnormal and IPG was normal; and group 4, both tests were abnormal. Phlebography (using the Rabinov and Paulin technique) or compression ultrasonography (the diagnostic standards in groups 2, 3, and 4) were done. In group 1, anticoagulant therapy was withheld and patients were followed clinically for 3 months (the diagnostic standard).
Main outcome measures
Sensitivity and specificity.
18% of patients had DVT. For group 1 (n = 273), the rate of DVT was 1.5% and the likelihood ratio for the presence of disease if the test was positive (+LR) was 0.07 (95% CI 0.03 to 0.17). For groups 2 and 3 (n = 83), the rate of DVT was 33% and the +LR was 2.3 (CI 1.5 to 3.3). For group 4 (n = 42), the rate of DVT was 93% and the +LR was 61 (CI 21 to 182).
The combination of negative results on D-dimer assay and a normal impedance plethysmographic examination ruled out the diagnosis of deep venous thrombosis.
Source of funding: In part, Heart and Stroke Foundation of Canada; Ontario Ministry of Health; Fraser Fellowship for Thrombosis Research; Heart and Stroke Foundation of Ontario.
For article reprint: Dr. J.S. Ginsberg, McMaster University Medical Centre, 1200 Main Street West, Room 3W15, Hamilton, Ontario L8N 3Z5, Canada. FAX 905-521-4972.
Accurate and rapid diagnosis of DVT requires objective testing in addition to clinical evaluation. Noninvasive techniques, such as IPG or compression ultrasonography, have largely replaced the more costly and invasive phlebography for the diagnosis of proximal DVT. However, serial testing is required to detect extending calf vein thrombi if the initial test result is negative (1).
Levels of D-dimer, a plasmin-derived degradation product of cross-linked fibrin, are elevated in the plasma of patients with thromboembolic disease. The use of a quick and accurate blood test to detect D-dimer in conjunction with noninvasive testing for DVT might obviate the need for serial noninvasive testing when the initial result is negative.
In the study by Ginsberg and colleagues, the combination of normal IPG results and negative D-dimer test results could effectively rule out DVT, which occurred in most (69%) of the patients studied. The negative predictive value of this combination of testing in this population was 98.5%.
This study differs from most of the previous studies because it did not involve the conventional ELISA, which requires laboratory expertise and takes several hours to perform, or latex agglutination assay, which also requires laboratory expertise and lacks sensitivity (2). The whole-blood agglutination assay used in this study is easier and faster to do; it also has a high sensitivity and negative predictive value (3, 4). The negative predictive value for D-dimer testing alone was 97.2%.
Therefore, the results of initial combination testing of D-dimer and IPG or compression ultrasonography can be used to make treatment decisions for most patients with suspected DVT without the need for additional testing. The practice of withholding anticoagulation therapy on the basis of D-dimer testing alone requires further study.
Scott A. Kolander, MD
University of Pennsylvania Health SystemPhiladelphia, Pennsylvania, USA
Scott A. Kolander, MD
University of Pennsylvania Health System
Philadelphia, Pennsylvania, USA
1. Huisman MV, Buller HR, ten Cate JW, Vreeken J. Serial impedance plethysmography for suspected deep venous thrombosis in outpatients. The Amsterdam General Practitioner Study. N Engl J Med. 1986;314:823-8.