The Wells’ DVT Criteria can be used in the outpatient and emergency department. By risk stratifying to low risk (Wells’ Score <2) and a negative D-dimer the clinician can exclude the further ultrasound (US) diagnostic test to rule out DVT.

The Wells’ Score is less useful in hospitalized patients.

The physician may not prescribe an ultrasound (ultrasound) to rule out DVT if the patient has low-risk DVT (<2 points) based on risk stratification on Wells` score and negative D-dimer.

The Wells’ scale should only be used after a detailed patient’s history taking and a physical examination in patients who are at risk of DVT.

The Wells’ Deep Vein Thrombosis (DVT) Risk Criteria stratifies patients by risk of DVT. There is a low prevalence of DVT in patients with a low pretest probability of DVT (<25%). Complications of DVT include pulmonary embolism (PE) and pulmonary hypertension, the mortality rate of which is 1-8%, so the timely diagnosis of DVT is the best prevention of PE and pulmonary hypertension.

Traditional diagnosis of DVT involves ultrasonography of the lower extremities, which is associated with time and financial resources. Using Wells` DVT criteria physicians can identify those patients who are generally unlikely have DVT. Further testing of patients for D-dimer can also safely rule out DVT without the necessity for an ultrasound.

The predictive scale includes nine parameters and the clinician’s clinical judgment regarding the likelihood of an alternative diagnosis.Well’s assessment score based on addition of the selected points:

Variable	Points
Active cancer (treatment or palliation within 6 months)	1
Bedridden recently >3 days or major surgery within 12 weeks	1
Calf swelling >3 cm compared to the other leg (measured 10 cm below tibial tuberosity)	1
Collateral (nonvaricose) superficial veins present	1
Entire leg swollen	1
Localized tenderness along the deep venous system	1
Pitting edema, confined to symptomatic leg	1
Paralysis, paresis, or recent plaster immobilization of the lower extremity	1
Previously documented DVT	1
Alternative diagnosis to DVT as likely or more likely	-2

There are a few versions of the criteria with minor differences between them. This is the most widely validated scale, based on Wells 2003.

Interpretation:

Шкала Wells’	Risk group	Prevalence of DVT	Recommendations
≤0	Low/unlikely	5%	These patients should proceed to D-dimer testing: • A negative high or moderate sensitivity D-dimer results in a probability <1 % and no further imaging is required • A positive D-dimer should proceed to US testing • A negative US is sufficient for DVT rule out • A positive US is concerning for DVT; strongly consider treatment with anticoagulation
1-2	Moderate	17%	These patients should proceed to high-sensitivity D-dimer testing (moderate sensitivity D-dimer is not sufficient) • A negative high-sensitivity D-dimer is sufficient for rule out of DVT in a moderate risk patient with a probability of <1% • A positive high sensitivity D-dimer should proceed to US testing • A negative US is sufficient for ruling out DVT • A positive US is concerning for DVT, strongly consider treatment with anticoagulation • Moderate risk group should only undergo D-dimer testing for rule out without ultrasonography if a high-sensitivity D-dimer is being used
≥3	High/likely	17-53%	All DVT likely patients should receive a diagnostic US • D-dimer testing should be utilized to help risk-stratify these DVT-likely patients • In DVT likely patients with negative D-dimer: • A negative US is sufficient for ruling out DVT, consider discharge • A positive US should be concerning for DVT, strongly consider treatment with anticoagulation •In DVT likely patients with a positive D-dimer: • A positive US should be concerning for DVT, strongly consider treatment with anticoagulation • A negative US is still concerning for DVT. A repeat US should be performed within 1 week for re-evaluation

Sometimes patients with DVT and a negative D-dimer are revealed in clinical practice.

• A negative ultrasound result is sufficient to rule out DVT and consider discharge.
• A positive ultrasound result indicates the presence of DVT, with the necessity of anticoagulants treatment.

With DVT and positive D-dimer:

• A positive ultrasound result is sufficient to make a diagnosis of DVT necessity of anticoagulants treatment.
• Negative ultrasound may also occur with DVT. A follow-up ultrasound should be performed within 1 week for re-evaluation.

This predictive score was derived from a series of studies by Wells’ et al. (Wells 1995, Wells 1997, Wells 2003) in an attempt to stratify the risk of DVT in symptomatic outpatients in order to reduce clinical resource burden and avoid overuse of imaging.

This scale has been included in the American College of Pulmonology guidelines for DVT.

NB!

• The clinician’s clinical assessment should take precedence over the score on this predictive scale. High suspicion for DVT should require imaging regardless of Wells’ score.
• The presence of DVT is critical in assessing the presence of PE, and if PE is being differentiated, alternative decision-making tools such as the Wells’ PE score or the PERC rule should be used.

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Sources:

1. Wells PS, Hirsh J, Anderson DR, et al. Accuracy of clinical assessment of deep-vein thrombosis. Lancet. 1995;345(8961):1326-30.https://pubmed.ncbi.nlm.nih.gov/7752753/
2. Wells PS, Anderson DR, Bormanis J, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet. 1997;350(9094):1795-8. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(97)08140-3/fulltext
3. Wells PS, Anderson DR, Rodger M, Forgie M, Kearon C, Dreyer J, Kovacs G, Mitchell M, Lewandowski B, Kovacs MJ. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med. 2003 Sep 25;349(13):1227-35. https://pubmed.ncbi.nlm.nih.gov/14507948/
4. Scarvelis D, Wells PS. Diagnosis and treatment of deep-vein thrombosis. CMAJ. 2006 Oct 24;175(9):1087-92. Review. Erratum in: CMAJ. 2007 Nov 20;177(11):1392. https://pubmed.ncbi.nlm.nih.gov/17060659/
5. Wells PS, Owen C, Doucette S, Fergusson D, Tran H. Does this patient have deep vein thrombosis? JAMA. 2006 Jan 11;295(2):199-207. Review. https://pubmed.ncbi.nlm.nih.gov/16403932/
6. Bates SM, Jaeschke R, Stevens SM, Goodacre S, Wells PS, Stevenson M.D., Kearon C, Schunemann HJ, Crowther M, Pauker SG, Makdissi R, Guyatt GH. Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. https://pubmed.ncbi.nlm.nih.gov/22315267/
7. Silveira PC, Ip IK, Goldhaber SZ, Piazza G, Benson CB, Khorasani R. Performance of Wells Score for Deep Vein Thrombosis in the Inpatient Setting. JAMA Intern Med. 2015 Jul;175(7):1112-7. doi: 10.1001/jamainternmed.2015.1687. https://pubmed.ncbi.nlm.nih.gov/25985219/

See also:

Well’s criteria for Pulmonary Embolism probability assessment

PERC Rule for Pulmonary Embolism- online calculator