CYP2A6 and Decreased total neutrophil count: However, comparison of the frequencies of diarrhoea and neutropenia between wild type and variants revealed that the CYP2A6 *1/*1 genotype was not significantly associated with any grade of diarrhoea (wild type, 5 out of 13, vs variant type, 7 out of 35; P=0.0740) or neutropenia (wild type, 4 out of 13, vs variant type, 7 out of 35; P=0.396).