Deep vein thrombosis can be ruled out in patients with the help of a clinical decision rule and a D-dimer test, according to a report in Seminars in Thrombosis and Hemostasis.
“No symptom or sign of deep vein thrombosis is specific for the disease, and most of them can be caused by more common disorders such as muscle tear, cellulitis or edema. This often confuses the status of deep vein thrombosis,” Ruud Oudega, MD, coordinator of diagnostic research on deep vein thrombosis and pulmonary embolism in primary care at the Julius Center University Medical Center in the Netherlands, said in an interview.
Oudega said the current assessment applies to patients in a primary care setting. Patients in secondary care are already evaluated and referred by other physicians and will have more evident symptoms.
The primary care model requires physicians to conduct a clinical assessment and assign a single point for each of the following characteristics: male gender, oral contraceptive use, presence of malignancy, recent surgery, absence of trauma or vein distension. If the patient presents with a calf circumference difference of at least 3 cm then that patient should be given an additional two points. The highest number of points, six, is given for an abnormal D-dimer test.
“The D-dimer test establishes the presence of degradation products of a thrombus,” Oudega said.
If a patient has a score of less than or equal to three after all measures are taken, then a primary care physician can safely rule out DVT. A score of at least four, however, should be followed up by compression ultrasonography. If the subsequent ultrasound is positive, patients should be treated immediately. However, if the test is negative, a repeat compression ultrasonography should be performed at one week. If the test is still negative, then DVT can be safely excluded.
Oudega and colleagues validated this rule among 1,295 primary care patients who were suspected of having deep vein thrombosis. Of the entire cohort, 23% fell into the very low-risk category, and only 0.7% of these had DVT. Low risk, defined as a score between four and six, represented 5% of the patients. Of those, 4.5% had DVT. Moderate risk patients (score seven to nine) comprised 51% of the group and 21.7% of them had DVT. Finally, among the high-risk patients, those with scores between 10 and 13, comprised 21% of the group, and of those, 51.3% of patients had DVT.
“D-dimer tests are sensitive but not very specific, so the test is most valuable in ruling out the disease, not proving the diagnosis,” Oudega said.
According to the research abstract, approximately 70% to 80% of patients who are referred for DVT do not actually have it. – by Jeremy Moore
For more information:
- Oudega R, Hoes AW, Toll DB, Moons KGM. The value of clinical findings and D-dimer tests in diagnosing deep vein thrombosis in primary care. Semin Thromb Hemost. 2006;32:673-677.