One blood sampling during the study. A small number (1 to 5) of markers type "tag SNPs" or "coding SNP" will be selected for each of the selected genes, for a total of 50 markers (representing 20 to 25 genes). Non-silent coding SNP, that may have a functional effect, will be included as a priority. Genotyping is carried out by the method of genotyping VeraCode Goldengate.