Validation of the LET classification

Introduction Acute thrombus removal therapies may reduce post-thrombotic syndrome in certain deep venous thrombosis patients. The LET classification is designed to identify patients at high risk for developing post-thrombotic syndrome in the acute phase using thrombus location and extent. This study evaluates the use of the LET classification to predict post-thrombotic syndrome in a cohort of patients after deep venous thrombosis. Methods A cohort of 660 deep venous thrombosis patients was invited to participate and fill out a questionnaire with Quality of life questionnaires, basic information, a modified self-assessment version of the Villalta scale for post-thrombotic syndrome and potential confounders. Original data on thrombus extension was available, and the LET classes were determined. Obtained information was analysed using ANOVA and in a multiple logistic regression model to correct for confounders. All different LET classes were compared to post-thrombotic syndrome occurrence, post-thrombotic syndrome prediction and disease specific quality of life scores (VEINES-Sym/Qol). Results Three hundred and fifteen patients responded, and in 309 a post-thrombotic syndrome score was distilled. LET I,II,III (n=63) had an odds ratio of 3.4(1.2-9.2) for predicting severe post-thrombotic syndrome, and LET II (n=17) had an odds ratio of 5.1(1.3-20.8) compared to LET class I (n=97). Both the VEINES-Sym and VEINES-Qol score were significantly lower for LET I,II,III compared to LET I, and LET II compared to LET I. Conclusion The LET classification can be used to classify patients according to acute thrombus location and extent. Extensive and centrally located (LET I,II,III) deep venous thrombosis showed the highest probability in developing severe post-thrombotic syndrome and lower disease specific quality of life.