To asses the cost-effectiveness of implementing different diagnostic strategies in patients with clinical assessment of suspected deep vein thrombosis (DVT) at first presentation in primary care. To evaluate the utility of using D dimer test to diagnose DVT in primary care. To describe the differential diagnosis and the strength of association between each outcome variable and the clinical prediction guide and the final diagnosis. It is a cross-sectional, multicentric study.

The participants are the patients referred from the 15 primary care centers (400.000 inhabitants) to the Hospital de la Santa Creu i Sant Pau emergency department with suspected DVT. We will enter physical examination and anamnesis variables, Wells and Oudega's rules variables, D-Dimer value and ultrasonography result. The outcome variables are the cost (€) of each possible way of diagnostic approach and the effectiveness will be measured by the ultrasonography result, which confirms or excludes the diagnosis. The sample will include 437 patients. A decision tree will be developed to analyze the different diagnostic options in DVT cases, using standard notation.

Inclusion Criteria:

• Patients referred by physicians with clinical suspicions of a first episode of deep vein thrombosis visited in emergency department of Hospital Santa Creu i Sant Pau

Exclusion Criteria:

• anticoagulant treatment
• patients who will not be able to follow control visit
• patients with oncologic treatment

Patients referred by physicians with clinical suspicions of a first episode of deep vein thrombosis visited in emergency department of Hospital Santa Creu i Sant Pau