• losartan;
  • nephritic syndrome;
  • proteinuria;
  • prothrombotic state;
  • thrombin generation

Summary. Background: Overt proteinuria is a strong risk factor for thromboembolism, owing to changes in the levels of various coagulation proteins and urinary antithrombin loss. The described coagulation disturbances in these patients are based on outdated studies conducted primarily in the 1970s and 1980s. Whether these coagulation disturbances resolve with antiproteinuric therapy has yet to be studied. Methods: A total of 32 patients with overt proteinuria (median, 3.7 g day−1; interquartile range, 1.5–5.6) were enrolled in this intervention crossover trial designed to assess optimal antiproteinuric therapy with sodium restriction, losartan, and diuretics. Levels of various procoagulant and anticoagulant proteins, and parameters of two thrombin generation assays (calibrated automated thrombogram [CAT] and prothrombin fragment 1 + 2) were compared between the placebo period and the maximum antiproteinuric treatment period. As a secondary analysis, coagulation measurements of the placebo period in these patients were compared with those of 32 age-matched and sex-matched healthy controls. Results: Median proteinuria was significantly lower during the maximum treatment period (median, 0.9 g day−1; interquartile range, 0.6–1.4; P < 0.001) than during the placebo period. Similarly, levels of various liver-synthesized procoagulant and anticoagulant proteins, activated protein C resistance and prothrombin fragment 1 + 2 levels were significantly lower during the maximum treatment period than during the placebo period. However, von Willebrand factor and factor VIII levels were similar. On the basis of the higher levels of procoagulant proteins (fibrinogen, FV, FVIII, and von Willebrand factor) and both thrombin generation assays, patients were substantially more prothrombotic than healthy controls (P < 0.004). Conclusions: Antiproteinuric therapy ameliorates the prothrombotic state. Proteinuric patients are in a more prothrombotic state than healthy controls.