On the basis of CYP expression in leukocytes, hepatic activities of CYP1A2, CYP2C9, CYP2C19 and CYP3A4 were also estimated in patients with end-stage renal disease and in organ donors using the cut-off values for distinction of poor, intermediate and extensive metabolizers described by Temesvári et al. [13]. This evidence concerns the gene CYP2C19 and chronic kidney disease.