Deep Venous Thrombosis Risk Stratification

Clinical Parameter	Score
Active cancer (treatment ongoing, or within 6 mo or palliative)	+1
Paralysis or recent plaster immobilization of the lower extremities	+1
Recently bedridden for >3 d or major surgery < 4 wk	+1
Localized tenderness along the distribution of the deep venous system	+1
Entire leg swelling	+1
Calf swelling >3 cm compared with the asymptomatic leg	+1
Pitting edema (greater in the symptomatic leg)	+1
Previous DVT documented	+1
Collateral superficial veins (nonvaricose)	+1
Alternative diagnosis (as likely or greater than that of DVT)	-2
Total of Above Score
High probability	≥3
Moderate probability	1 or 2
Low probability	≤0
*Adapted from JAMA. 1998 Apr 8;279(14):1094-9.[1]

Deep Venous Thrombosis Risk Stratification
The Wells clinical prediction guide quantifies the pretest probability of deep venous thrombosis (DVT) (see Table). The model enables physicians to reliably stratify patients into high-, moderate-, or low-risk categories. Combining the pretest probability with the results of objective testing greatly simplifies the clinical workup of patients with suspected DVT. The Wells clinical prediction guide incorporates risk factors, clinical signs, and the presence or absence of alternative diagnoses.

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Table. Wells Clinical Score for Deep Venous Thrombosis* (Open Table in a new window)

Clinical Parameter Score
Active cancer (treatment ongoing, or within 6 mo or palliative) +1
Paralysis or recent plaster immobilization of the lower extremities +1
Recently bedridden for >3 d or major surgery < 4 wk +1
Localized tenderness along the distribution of the deep venous system +1
Entire leg swelling +1
Calf swelling >3 cm compared with the asymptomatic leg +1
Pitting edema (greater in the symptomatic leg) +1
Previous DVT documented +1
Collateral superficial veins (nonvaricose) +1
Alternative diagnosis (as likely or greater than that of DVT) -2
Total of Above Score
High probability ≥3
Moderate probability 1 or 2
Low probability ≤0
*Adapted from JAMA. 1998 Apr 8;279(14):1094-9.[1]
Using the pretest probability score calculated from the Wells DVT score, patients are stratified into 2 risk groups: DVT unlikely (DVT score < 2) or DVT likely (DVT score ≥2).

This risk group stratification is then considered in concert with the results of a sensitive D-dimer assay such as the VIDAS rapid enzyme-linked immunoabsorbent assay (ELISA). A negative D-dimer result rules out DVT in the unlikely group (low-to-moderate risk of DVT). Even if the D-dimer test is negative, patients in the likely group (moderate-to-high risk of DVT) require a diagnostic study (ie, duplex ultrasonography), as do all patients with a positive D-dimer result.

In a patient who is scored as unlikely to have DVT, a negative duplex ultrasonographic study result rules out DVT, even if the D-dimer assay is positive. If the duplex findings are positive in a patient who is scored as likely, treat for DVT. When discordance exists between the pretest probability and the duplex ultrasonographic study result, further evaluation is required.

If the patient is scored as likely to have DVT (DVT score ≥2) but the ultrasonographic findings are negative, the patient still has a significant probability of DVT. Duplex ultrasonography is relatively insensitive for calf vein thrombosis, so some authors recommend venography to rule out a calf vein DVT that ultrasonography did not detect. Most recommend surveillance with repeat clinical evaluation and ultrasonography in 1 week. Others use the results of the D-dimer assay to guide management. A negative D-dimer assay in combination with negative ultrasonographic findings rules out DVT. A positive D-dimer assay in this group mandates surveillance and repeat ultrasonography in 1 week.

If the patient is scored as unlikely to have DVT (DVT score < 2) but the ultrasonographic findings are positive, some authors recommend a second confirmatory study such as venography before treating for DVT and committing the patient to the risks of anticoagulation. Most, however, treat the patient for DVT.

If the patient is scored as likely to have DVT (DVT score ≥2) and had a positive D-dimer assay result but the ultrasonographic findings are negative, repeat clinical evaluation and ultrasonography in 1 week is recommended.

The DVT score was developed in a specific subgroup of patients. Excluded from the model were patients with suspected coexistent PE and patients already taking anticoagulants. Therefore, the evaluation and subsequent treatment of these excluded subgroups must be individualized.

For more information, see Deep Venous Thrombosis.