Wells Score For DVT

Wells score explained

This clinical decision making tool helps reduce unnecessary ultrasound investigations in patients who are unlikely to develop deep venous thrombosis. The items in the score account for the major DVT risk factors:

1) Lower limb trauma, surgery or plaster – risk of vessel damage and more.

2) Immobilization for more than 3 days or surgery within last month – blood stagnation risk.

3) Tenderness along femoral or popliteal veins.

4) Entire limb swelling.

5) Non varicose dilatation of collateral superficial veins.

6) Calf more than 3cm bigger circumference, 10cm below tibial tuberosity – specific DVT sign.

7) Pitting edema – specific DVT symptom.

8) History of confirmed DVT – patient or family history increase risk.

9) Malignancy – in treatment or not for the past six months is considered a risk factor.

10) Intravenous drug use - particularly involving groin injection.

11) Alternative diagnosis more likely than DVT.

DVT differential diagnosis occurs with the following: external venous compression, muscle damage due to trauma or other pathology, superficial venous thrombosis, inguinal lymphadenopathy, post phlebitic syndrome or cellulites.

DVT likelihood interpretation

All items in the Wells score are awarded 1 point when positive, except for item 10 (intravenous drug use) which is awarded 3 points and item 11 (alternative diagnosis more likely than DVT) which subtracts 2 points from the score.

Therefore, the Wells scores range from – 2 to 12. The table below explains the risk groups proposed by the model and the diagnosis pathways:

As a risk stratification tool, Wells score defines risk of DVT as likely and unlikely, depending on the score.

According to the table above, for scores below 1, DVT is unlikely and has a 5% probability of occurring.

When the score is accompanied by a negative D-dimer test, the patient is not required to undergo ultrasound investigation, thus reducing the cost of unnecessary clinical determinations.

When the score is accompanied by a positive D-dimer test, the patient needs to undergo ultrasound testing.

For scores of 1 and 2, DVT is still deemed unlikely, but with a 17% moderate probability of occurring. When these scores are accompanied by a negative D-dimer, ultrasound is not necessary, unless the clinician judges that it could eliminate any suspicion.

When the score is accompanied by a positive D-dimer, ultrasound is compulsory.

Patients obtaining scores greater than 2 are at 35%, high probability of developing DVT. In these cases, ultrasound testing is necessary to eliminate suspicion when D-dimer is negative and compulsory when D-dimer is positive.

About the study

The score was developed in 2003 by Wells et al. following a study on 1096 outpatients suspected of DVT and randomized in two groups after being administered the Wells score.

■ 562 patients underwent D-dimer testing;

■ 520 patients had an ultrasound.

Patients with positive D-dimer results also underwent ultrasound testing. The overall incidence of DVT in the ultrasound cohort of patients was 15.7%. Only 1.4% of patients who underwent ultrasound testing and were initially ruled out, had a diagnosis of DVT in 3 months.

The negative predictive value of D-dimer was 96.1%.

The conclusion of the study was that the score is an accurate prediction tool and that DVT can be ruled out in patients that score unlikely and whose D-dimer test result is negative.

DVT warning signs

Deep venous thrombosis is a condition in which blood clots form in the deep veins of the body, usually in the legs (the calf or thigh).

The first sign of DVT is swelling and pain. The blood clots risk rupturing and from there can travel through the bloodstream towards the lungs (venous thromboembolism), leading to pulmonary hypertension and a pulmonary embolism.

Other symptoms are warming, redness of the skin, tenderness and discomfort in calves.

DVT risk factors include:

■ Age;

■ Family history of blood clots;

■ Heart failure;

■ Damaged blood vessels;

■ Inactivity after surgery;

■ Trauma.

Deep venous thrombosis is a condition that doesn’t show symptoms in all cases but poses a life-threatening risk, especially in patients with several risk factors.

Original source

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; 349(13):1227-35.

Validation

Scarvelis D, Wells PS (2006) Diagnosis and treatment of deep-vein thrombosis. CMAJ. Oct 24;175(9):1087-92.

Other references

1. Wells PS, Owen C, Doucette S, Fergusson D, Tran H. Does this patient have deep vein thrombosis? JAMA. 2006; 295(2):199-207.

2. 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.