To diagnose CGD, reactive oxygen intermediates (O2− or H2O2) generated by the NADPH oxidase in peripheral blood phagocytes are measured upon in vitro activation with either phorbol-12-myristate-13-acetate (PMA) and/or TLR4 ligands (E. coli or LPS). This evidence concerns the gene FMO5 and chronic granulomatous disease.