Summary. Background: Few studies have evaluated the longterm economic consequences of deep vein thrombosis (DVT).None of them have incorporated prospectively collected clinical data to ensure accurate identification of incident cases of DVT and DVT-related health outcomes of interest, such as post-thrombotic syndrome (PTS). Objectives: To prospectively quantify medical and non-medical resource use and costs related to DVT during 2 years following diagnosis, and to identify clinical determinants of costs. Methods: Three hundred and fifty-five consecutive patients with acute DVT were recruited at seven Canadian hospital centers. Resource use and cost information were retrieved from three sources: weekly patient-completed cost diaries, nurse-completed case report forms, and the Quebec provincial administrative healthcare database (RAMQ). Results: The rate of DVT-related hospitalization was 3.5 per 100 patient-years (95% confidence interval [CI] 2.2-4.9). Patients reported a mean (standard deviation) of 15.0 (14.5) physician visits and 0.7 (1.2) other healthcare professional visits. The average cost of DVT was $5180 (95% CI $4344-6017) in Canadian dollars, with 51.6% of costs being attributable to non-medical resource use. Multivariate analysis identified four independent predictors of costs: concomitant pulmonary embolism (relative increase in cost [RIC] 3.16; 95% CI 2.18-4.58), unprovoked DVT (RIC 1.65; 95% CI 1.28-2.13), development of PTS during follow-up (RIC 1.35; 95% CI 1.05-1.74), and management of DVT in the inpatient setting (RIC 1.79; 95% CI 1.33-2.40). Conclusions: The economic burden of DVT is substantial. The use of measures to prevent the occurrence of PTS and favoring outpatient care of DVT has the potential to diminish costs.

The diagnostic approach to deep vein thrombosis (DVT) has evolved during the last 3 decades. Contrast venography has been replaced by noninvasive tests. Compression ultrasonography (CUS) is currently the most widely used diagnostic test. Whereas CUS has a high accuracy for proximal DVT (thrombosis of the popliteal and more proximal veins), it has been shown to lack sensitivity and specificity for distal DVT. Ultrasonography can either be limited to the proximal veins and repeated within 1 week (serial limited CUS) or extended to both proximal and distal veins and performed on one occasion (single complete CUS). Both strategies are reliable diagnostic options for the management of patients with suspected DVT. The main limitation of proximal CUS is the need to repeat the test once in patients with initial negative findings. Conversely, complete CUS detects many distal DVTs for which systematic anticoagulation therapy is debatable and exposes patients to potentially unnecessary anticoagulation. Incorporation of D-dimer testing and clinical pretest probability assessment in the diagnostic algorithm is beneficial because it allows excluding DVT without the need for diagnostic imaging in about a third of patients.

The post-thrombotic syndrome (PTS) is the most commonly occurring long-term complication of deep vein thrombosis (DVT) with a cumulative incidence of up to 50% within the first 2 years after the thrombotic event. It is characterized by the development of various symptoms and signs related to chronic venous disease in a limb previously affected by DVT. PTS is a condition that significantly impairs quality of life and results in substantial burden to patients and society. So far, treatment options for PTS are limited, and strategies that prevent PTS occurrence are therefore of pivotal importance. These include compression therapy, prevention of recurrent ipsilateral DVT and possibly endovascular catheter-directed thrombolytic procedures. Clinical predictors of PTS are progressively characterized, but the ability to predict which patient with DVT is likely to develop PTS remains limited.

566 Background and objectives: Deep venous thrombosis (DVT) is a common and serious vascular condition that is frequently complicated by the chronic post-thrombotic syndrome. Costs of DVT may occur over a long period and may be medical and non-medical in nature. During a Canadian multicenter cohort study of the long-term outcomes after DVT (The Venous Thrombosis Outcomes [VETO] Study), we prospectively quantified resource use and costs related to DVT during two years after DVT diagnosis, and identified clinical determinants of costs. Methods: The study population consisted of 355 consecutive patients diagnosed with objectively confirmed acute DVT at one of 7 participating hospitals in the province of Quebec, Canada. Using a societal perspective, we tracked total medical resource use (hospitalizations, physician visits, other health professional visits, medications, ambulance services, stockings, assistive devices) and non-medical resource use (loss of productivity, home care, transportation) incurred by DVT during the 2 years after diagnosis. Data sources included weekly patient-completed cost diaries, nurse-completed case report forms (baseline, 1, 4, 8, 12, 24 months and at any DVT-related clinical event) and the Quebec provincial administrative healthcare database (“RAMQ”). Resources for each patient were valued using individual patient level information obtained from RAMQ and patient diaries. Statistics Canada data, provincial health professionals associations and local suppliers were used to estimate resource costs if individual information was not available. The value of lost productivity was estimated using a friction-cost approach. Multivariate regression modeling for predictors of medical costs during 2 years included baseline demographic and clinical characteristics as well as the development of post-thrombotic syndrome (PTS) during study follow-up. Results: At study entry, mean age was 56.5 years, 50.1% were male, 2/3 were out-patients and 58.0% had proximal DVT. The mean duration of heparin and warfarin treatment was 7.6 days (SD 6.0) and 21.6 weeks (SD 10.0), respectively. During 2 years follow-up, the rate of DVT-related hospitalization was 3.5 per 100 patient-years (95% CI 2.2, 4.9). Patients reported, on average, 15.0 (SD 14.5) physician visits and 0.7 (SD 1.2) non-physician visits. Patients required 12.7 (SD 9.2) transportations, 38.6 (SD 138.0) hours of assistance and missed 12.1 (SD 39.8) workdays. The average per-patient total cost over 2 years was Can$4109 (95% CI $3658, $4561) with 63.7% of costs attributable to non-medical resource use. The two largest medical cost components were hospitalizations (Can$502; 95% CI $261, $744) and physician visits (Can$356; 95% CI $320, $392). More than two-thirds of all resource consumption occurred during the first 4 months after diagnosis. In multivariate analysis focusing on determinants of medical costs, concomitant pulmonary embolism (p = 0.002), idiopathic DVT (p= 0.003), and development of post-thrombotic syndrome during follow-up (p= 0.002) were independently associated with increased costs. Conclusion: The economic burden of DVT over the two years following initial diagnosis is substantial with almost two-thirds of costs attributable to non-medical resource use. Concomitant pulmonary embolism, idiopathic DVT, and development of PTS are important predictors of medical costs after DVT. Better adherence to thromboprophylaxis strategies and use of measures to prevent occurrence of PTS have the potential to diminish costs and resource utilization related to DVT. Disclosures: No relevant conflicts of interest to declare.