Recommendation 1
Validated clinical prediction rules should be used to estimate pretest probability of venous thromboembolism (VTE), both deep venous thrombosis (DVT) and pulmonary embolism, and for the basis of interpretation of subsequent tests.
Good quality evidence supports the use of clinical prediction rules to establish pretest probability of disease. The Wells prediction rules for DVT and for pulmonary embolism (see Tables below) have been validated and are frequently used to estimate the probability of VTE before performing more definitive testing on patients. The Wells prediction rule performs better in younger patients without comorbidities or a history of VTE than it does in other patients. Physicians should use their clinical judgment in cases where a patient is older or presents with comorbidities.
Table 1. Wells Prediction Rule for Diagnosing Deep Venous Thrombosis: Clinical Evaluation Table for Predicting Pretest Probability of Deep Vein Thrombosis
| Clinical Characteristic |
Score |
| Active cancer (treatment ongoing, within previous 6 months, or palliative) |
1 |
| Paralysis, paresis, or recent plaster immobilization of the lower extremities |
1 |
| Recently bedridden >3 days or major surgery within 12 weeks requiring general or regional anesthesia |
1 |
| Localized tenderness along the distribution of the deep venous system |
1 |
| Entire leg swollen |
1 |
| Calf swelling 3 cm larger than asymptomatic side (measured 10 cm below tibial tuberosity) |
1 |
| Pitting edema confined to the symptomatic leg |
1 |
| Collateral superficial veins (nonvaricose) |
1 |
| Alternative diagnosis at least as likely as venous thrombosis |
-2 |
Note: Clinical probability: low <0; intermediate 1–2; high >3. In patients with symptoms in both legs, the more symptomatic leg is used.
Reprinted from The Lancet, Vol 350, Wells PS, Anderson DR, Bormanis J, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management, pp 1795-8, Copyright 2002, with permission from Elsevier.
Table 2. Wells Prediction Rule for Diagnosing Pulmonary Embolism: Clinical Evaluation Table for Predicting Pretest Probability of Pulmonary Embolism
| Clinical Characteristic |
Score |
| Previous pulmonary embolism or deep vein thrombosis |
+ 1.5 |
| Heart rate >100 beats per minute |
+ 1.5 |
| Recent surgery or immobilization |
+ 1.5 |
| Clinical signs of deep vein thrombosis |
+ 3 |
| Alternative diagnosis less likely than pulmonary embolism |
+ 3 |
| Hemoptysis |
+ 1 |
| Cancer |
+ 1 |
Note: Clinical probability of pulmonary embolism: low 0–1; intermediate 2–6; high >7
Reprinted from Am J Med, Vol 113, Chagnon I, Bounameaux H, Aujesky D, et al, Comparison of two clinical prediction rules and implicit assessment among patients with suspected pulmonary embolism, pp 269-75, Copyright 2002, with permission from Elsevier.
Recommendation 2
In appropriately selected patients with low pretest probability of DVT or pulmonary embolism, obtaining a high-sensitivity D-dimer is a reasonable option, and if negative, indicates a low likelihood of VTE.
In selected patients who have a low pretest probability of VTE as defined by the Well prediction rules, a negative high-sensitivity D-dimer assay for VTE has sufficiently high negative predictive value to reduce the need for further imaging studies. Currently, enzyme-linked immunosorbent assay (ELISA), quantitative rapid ELISA, and advanced turbidimetric D-dimer determinations are highly sensitive assays (sensitivity 96% to 100%) and their use is practical in diagnosis of VTE. D-dimer testing has the highest negative predictive value when used to exclude VTE in younger patients without associated comorbidity or history of VTE and with short duration of symptoms, because the Wells criteria more accurately predict a low pretest probability of VTE in such patients. In older patients, those with associated comorbidity, and long duration of symptoms, a D-dimer alone may not be sufficient to rule out VTE.
Recommendation 3
Ultrasound is recommended for patients with intermediate to high pretest probability of DVT in the lower extremities.
Use of ultrasound in diagnosing symptomatic thrombosis in the proximal veins of the lower limb is recommended for patients whose pretest probability of disease falls in the category of intermediate to high risk of DVT under the Wells prediction rule. Ultrasound is less sensitive in patients who have DVT limited to the calf; therefore, a negative ultrasound does not rule out DVT in these patients. Repeat ultrasound or venography may be required for patients who have suspected calf-vein DVT and a negative ultrasound and for patients who have suspected proximal DVT and an ultrasound that is technically inadequate or equivocal. Contrast venography is still considered the definitive test to rule out the diagnosis of DVT.
Recommendation 4
Patients with intermediate or high pretest probability of pulmonary embolism require diagnostic imaging studies.
For patients who have intermediate or high pretest probability of pulmonary embolism, imaging is essential. Possible tests include ventilation-perfusion (V/Q) scan, multidetector helical computed axial tomography (CT), and pulmonary angiography. Recent systematic reviews indicate that CT alone may not be sufficiently sensitive to exclude pulmonary embolism in patients who have a high pretest probability of pulmonary embolism.
