I:T ratio = (bands+metamyelocytes+myelocytes) / (bands+metamyelocytes+myelocytes+neutrophils) (Bands, metamyelocyte and myelocyte counts are given as part of the manual differentiation of white blood cell count from most laboratories). Upper limits of normal: Day 1 – 0.16 Day 2 – 0.14 Day 3 onwards – 0.12 If I:T ratio > 0.2 and low neutrophil count or high CRP, then infection is likely.