Nitrite and nitrate plasma levels, as markers for nitric oxide synthesis, in thrombotic thrombocytopenic purpura (TTP). A case-control study

The enhanced platelet aggregation and thrombosis occurring in TTP is probably due to an unbalance between agents insulting endothelial integrity and natural antithrombotic factors, such as NO. Using a sensitive and specific HPLC assay, we tested the hypothesis of NO involvement in TTP, comparing NO production, as the stable end-products nitrites and nitrates, in the plasma of 29 TTP patients and of 29 healthy subjects matched for sex and age. Average nitrate titer was 25.868 μM/L in the TTP group vs 24.234 μM/L in the control group (p = n.s.), while nitrite were undetectable in both groups. Moreover, nitrate titers did not correlate with hemoglobin value, platelet count, LDH values, or with Rose and Elder's severity score. In conclusion, even though the enhanced platelet aggregation observed in TTP could be due to reduced natural antithrombotic substances, NO involvement in the pathogenesis of TTP appears unlikely.