The post-thrombotic syndrome: incidence and prognostic value of non-invasive venous examinations in a six-year follow-up study.

The ability to predict severity of the post-thrombotic syndrome (PTS) early after acute deep-vein thrombosis (DVT) is limited. The aim of our study was to examine the incidence of PTS prospectively and to evaluate the predictive value of non-invasive venous examinations shortly after DVT for the development of PTS. In 93 patients with DVT thrombosis score (TS), reflux, venous outflow resistance (VOR) and calf muscle pump dysfunction (CMP) were examined prospectively. After one, two and six years patients were evaluated for PTS using the clinical scale of the CEAP-classification (PTS present > or = 3 on a scale from 0 to 6). Area under the curves (AUC) were used to evaluate the predictive value of the non-invasive examinations at one and three months after diagnosis of DVT for future PTS. The cumulative incidence of PTS increased from 49% (32/65) after one year to 55% (36/65) and 56% (27/48) after two and six years, whereas the incidence of patients with PTS class 4 progressed from 20% after two years to 33% after six years. The prognostic value to predict PTS was highest for the combination of TS, VOR and reflux measured three months after diagnosis and showed an AUC of 0.77 (0.65-0.90) for PTS after one year. In conclusion, the incidence of PTS after DVT did not increase significantly after one year, whereas during longer follow-up the severity of PTS rose in patients with PTS. Moreover, measurement of TS, VOR and reflux three months after DVT could predict, with reasonable accuracy, the risk of PTS after one year of follow-up.