Deep vein thrombosis diagnosis

Editors-in-Chief: C. Michael Gibson, M.S., M.D. Associate Editor-In-Chief: Ujjwal Rastogi, MBBS [mailto:urastogi@perfuse.org]

Overview
A number of invasive (venography) and non-invasive tests are possible (impedance plethysmography, compression ultrasonography, D-dimer testing) for diagnosis. Compression ultrasonography is the noninvasive diagnosis of choice for a patients with a first episode of suspected DVT.

In a patient population with a high prevalence of venous thromboembolism, a negative D-dimer assay may be insufficient to rule out DVT as a single test, and moreover not all D-dimer assays are validated for this. However, a D-dimer level <500 ng/mL by ELISA along with a low clinical probability (Wells score) or other negative non-invasive tests may be useful in excluding DVT, without doing ultrasound.

In patients with a first episode of DVT, a positive noninvasive study usually confirms the diagnosis. Compression ultrasonography has a positive predictive value of 94 percent (95% CI: 87-98 percent). In situation where the initial investigation was negative but the clinical suspicion of DVT is high, a repeat study should be done within a week. Complete lower extremity ultrasonography may eliminate the need for repeat testing, but a positive compression ultrasonography demands user expertise, and requires specialized instrumentation.

Pretest probability
Many pretest probability scoring system are proposed for use in primary care patients, like Wells score, Hamilton score, and AMUSE score. When combined with pretest probability, ultrasonography and D-dimer tests are most useful in diagnosis for DVT.

Wells score
The Wells prediction rule is useful in identifying patients at low risk of being diagnosed with venous thromboembolism. Overall performance of the prediction rule is increased when combined with a rapid latex D-dimer assay.

In 2006, Scarvelis and Wells overviewed a set of clinical prediction rules for DVT, on the heels of a widely adopted set of clinical criteria for pulmonary embolism.

Wells score: (Possible score -2 to 9)
 * 1) Active cancer (treatment within last 6 months or palliative) +1 point
 * 2) Calf swelling >3 cm compared to other calf (measured 10 cm below tibial tuberosity) +1 point
 * 3) Collateral superficial veins (non-varicose) +1 point
 * 4) Pitting edema (confined to symptomatic leg) +1 point
 * 5) Previous documented DVT +1 point.
 * 6) Swelling of entire leg +1 point
 * 7) Localized pain along distribution of deep venous system +1 point
 * 8) Paralysis, paresis, or recent cast immobilization of lower extremities +1 point
 * 9) Recently bedridden > 3 days, or major surgery requiring regional or general anesthetic in past 4 weeks +1 point
 * 10) Alternative diagnosis at least as likely -2 points

Interpretation:

Limitations of Wells score

 * The accuracy of the Wells rule, though useful in secondary and tertiary care centers, has not been properly validated for use in primary care patients with the suspicion of DVT.
 * The performance of Wells score was decreased when evaluating elderly patients or those with a prior DVT or having those having other comorbidities, which might be equivalent to what is found in a primary care setting. Also, it should be highlighted that Wells criteria is an additional tool to diagnosis rather than being a stand-alone test.

Hypercoaguable state
Hypercoagulable state should be suspected in a young patient (i.e. less than 50 years of age) having DVT. Also a combination of pathogenic factors contribute to the disease. The presence or absence of an inherited thrombophilia does not usually change the decision, regarding length of anticoagulation therapy. Family members of patient with an inherited thrombophilia could be identify, but anticoagulant prophylaxis is rarely recommended in asymptomatic affected family members, except in high risk situations. To read more about hypercoaguablity, click here.