Methods:

The SOX trial investigators conducted a multicenter, randomized, placebo-controlled trial of active versus placebo ECS used for 2 years to prevent post-thrombotic syndrome (PTS) after a first proximal deep venous thrombosis (DVT) in centers in Canada and the USA. Patients were randomly assigned to study groups with a web-based randomization system. Patients presenting with a first symptomatic, proximal DVT were potentially eligible to participate. They were excluded if the use of compression stockings was contraindicated, they had an expected lifespan of less than 6 months, geographical inaccessibility precluded return for follow-up visits, they were unable to apply stockings, or they received thrombolytic therapy for the initial treatment of acute DVT. The primary outcome was PTS diagnosed at 6 months or later using Ginsberg’s criteria (leg pain and swelling of ≥1 month duration). The authors used a modified intention-to-treat Cox regression analysis, supplemented by a prespecified per-protocol analysis of patients who reported frequent use of their allocated treatment.