It is noteworthy that 33.3% of patients homozygous for the UGT1A1*28 allele developed severe neutropenia and diarrhoea at the same time, whereas only 1.8% of UGT1A1*1/*1 and 5.2% of UGT1A1*1/*28 patients did so (OR=12.38, 95% CI=2.38–54.18, P<0.0001, Supplementary Table S1). Here, UGT1A1 is linked to Decreased total neutrophil count.