Diagnose DVT and treat (see recommendations 16 to 27) patients with a positive proximal leg vein ultrasound scan.

Relative values of different outcomesThe number of DVT cases correctly diagnosed (true positives) and the number of false positives (when treatment may be started incorrectly) are the most important outcomes. It is also important that patients start treatment as soon as the diagnosis is confirmed.
Trade off between clinical benefits and harmsProximal leg vein ultrasound scans are used as confirmatory tests in this pathway. Evidence showed that based on the specificity of proximal leg vein ultrasound scan, this test is suitable for the purpose of confirming the presence of DVT.
Both sensitivity and specificity are important in order to ensure all DVTs are detected and patients with DVT are treated. The GDG had recommended proximal leg vein ultrasound scans as the clinical importance of picking up extra calf blood clots through whole leg scan is uncertain.
Economic considerationsBased on a decision model comparing different sequences of tests, a strategy where diagnosis of DVT is confirmed by ultrasound is cost-effective.
Quality of evidenceThe quality of evidence ranged from very low to moderate for the various ultrasound strategies reviewed. These studies showed that ultrasound scans have high specificities, which makes them effective in confirming the presence of DVT. However, the sensitivity of the tests can vary a little between studies and average around 90%.
The economic evidence has potentially serious limitations and partial applicability.
Other considerationsIt is important to diagnose and confirm DVT quickly. Treatment with LMWH exposes patients to side effects and is expensive (cost of drug and district nurse time). It is important not to put patients needlessly on LMWH.
The GDG also discussed that ultrasound techniques have important limitations in visualising iliac vein thrombosis. The current clinical understanding is this technique may not be effective if the relatively unusual situation of isolated iliac vein thrombosis is suspected. If this is suspected (for example, from changes in blood flow in the femoral vein), the usual practice is to investigate with other imaging methods such as CT or MR venography.
See also recommendations on treatment of DVT.

From: 5, Diagnosis of deep vein thrombosis

Cover of Venous Thromboembolic Diseases
Venous Thromboembolic Diseases: The Management of Venous Thromboembolic Diseases and the Role of Thrombophilia Testing [Internet].
NICE Clinical Guidelines, No. 144.
National Clinical Guideline Centre (UK).
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