Presenting D-dimer and early symptom severity are independent predictors for post-thrombotic syndrome following a first deep vein thrombosis. 
Post-thrombotic syndrome (PTS) is the most common complication of deep vein thrombosis (DVT).  Current preventative strategies are limited to the daily wear of graduated compression stockings (GCS).  The aim of this study was to evaluate early predictors of PTS.  One hundred and twenty-two consecutive patients with a first DVT were prospectively recruited from diagnosis and followed for up to 6 months post-end of anticoagulation.  D-dimer was measured in 107 participants at presentation and Villalta scale was evaluated in 70 participants at a median of 2 weeks following diagnosis.  PTS developed in 51·6% of participants.  GCS were obtained by 78·1% of participants, with 33·7% reporting daily wear at the end of follow-up.  Mean early Villalta scale was significantly higher in those with PTS (8·1 ± 3·7) compared to those without (2·6 ± 2·7, P < 0·001).  Median D-dimer was significantly higher in those with PTS [3260 ng/ml, interquartile range (IQR) 820-8000 ng/ml] compared to those without (1540 ng/ml, IQR 810-2520 ng/ml, P < 0·001).  The adjusted odds ratio for every one point increase in early Villalta scale was 1·78 [95% confidence interval (CI), 1·19-2·64; P = 0·005] and for D-dimer >1910 ng/ml it was 2·71 (95% CI, 1·05-7·03; P = 0·04).  These markers could enable targeted counselling regarding GCS for those at high risk of PTS.