Predictors Of The Post-Thrombotic Syndrome In a Large Cohort Of Patients With Proximal DVT: Secondary Analysis Of The Sox Trial

![Graphic][1] Background The post-thrombotic syndrome(PTS) is a frequent complication of deep venous thrombosis (DVT). Identifying predictors of PTS is important to counsel DVT patients on their expected prognosis and to identify patients who may benefit from closer monitoring or preventive strategies. Objective In a secondary analysis of the SOXTrial, we aimed to identify predictors of developing PTS during 2 years follow-up after a first episode of proximal DVT. Methods The study cohort consisted of participants in the SOXTrial, a multicenter (24 centres in Canada and U.S.) randomized placebo controlled trial of active elastic compression stockingsvs. placebo stockings worn for 2 years after a first, symptomatic proximal DVT. PTS, the primary study endpoint, was diagnosed at or after the 6 month visit based on patient-reported pain and swelling of ≥ 1 month duration that were typical in character, i.e. worse at endof dayor after prolonged sitting/standing and improved after rest/leg elevation (Ginsberg criteria). Cumulative incidencesof PTS were compared in subgroups defined by sex, age category, body mass index (BMI) category, anatomic extent of index DVT, type of DVT (cancer-associated, secondary risk factor-associated, unprovoked) and 1-month Villalta score category (score 0-4: none; 5-9, mild; 10-14, moderate; >14, severe), using Cox regression. Losses to follow-up, withdrawals and deaths were censored as of last date of follow-up. Results are presented as cumulative incidenceby 750 days follow-up and hazard ratios (HR) with 95% confidence intervals (CI). Results Among the 803 participants in the SOXTrial, 60% were male, mean age was 55.1 years, and 87% were out-patients. In analyses adjusted for intervention group (i.e. allocation to active vs. placebo stockings), iliac veinDVT (HR 2.26 [95% CI 1.12, 4.53]; reference category: popliteal DVT) and Villalta score category at 1 month after DVT (score 5-9, HR 2.74 [95% CI 1.62, 4.64]; score 10-14, HR 5.81[95% CI 2.99, 11.29]; score >14, HR 7.59 [95% CI 3.31, 17.44]; reference category: score <5) were significant predictors of PTS. In analyses adjusted for intervention group and all predictor variables of interest, Villalta score category at 1 month was a highly statistically significant, independent predictor of PTS ( see [Table][2] ). Age, sex, BMI and type of DVT did not predict development of PTS. View this table: Table Conclusions In a large prospective cohort of patients with proximal DVT who were participants in the SOXTrial, Villalta score category (which reflects severity of venous symptoms and signs) at 1 month after DVT was strongly predictive of development of PTS during 2 years follow-up. This confirms a similar finding that we first observed in the VETOcohort study (Kahn SR et. al., Annals Intern Med 2008). More extensive DVT was also associated with PTS. Patients with these risk factors may benefit from closer monitoring after proximal DVT, and in the case of iliac veinDVT, from more aggressive strategiesto treat acute DVT. Disclosures: No relevant conflicts of interest to declare. [1]: /embed/inline-graphic-2.gif [2]: #T1