Moreover, the UGT1A1 genotype of the patient, and the activity of the gut microbial enzyme β-glucuronidase (GUS) have been suggested as biomarkers for the development of systemic (e.g. neutropenia) and gastrointestinal toxicity (e.g. diarrhea) respectively. This evidence concerns the gene UGT1A1 and Decreased total neutrophil count.