Objective The validity of the immature-to-total granulocyte ratio (IT) has been questioned, as there is a marked variation in manual cell counts, especially band counts, depending on the technician. We aimed to determine whether the modified IT ratio was a better predictor of late-onset sepsis in very low birth weight infants (VLBW).

Methods 183 Full blood counts (FBC) and paired blood cultures (BC) from 56 infants <1500 g >48 hours of age were available for analysis from January to July 2007. A modified IT ratio was calculated by excluding bands from the numerator. Unlike other studies, sepsis episodes due to commensal organisms were included as they are responsible for significant clinical signs and symptoms in VLBW infants.

Results There were 69 positive and 114 negative blood cultures in infants with a gestation of (mean +/− SD) 26+/−1 versus 27+/−1.4 weeks respectively. Both the absolute neutrophil count (ANC) and the traditional IT ratio (neutrophil indices: culture positive 0.22+/−0.2; culture negative 0.12+/−0.16; p 0.0005) were predictive of culture-positive sepsis (p<0.05). The absolute neutrophil count, absolute number of immature granulocytes, band forms, C-reactive protein (CRP) and platelets (p<0.05) were significantly associated with positive blood cultures. The modified IT (NS) was not. The only significant difference in blood parameters between infants with Staphylococcal commensals and other pathogenic bacteria (e.g. E.coli, Klebsiella) was the CRP (p<0.05).

Conclusions Traditional IT ratio was a better predictor of late-onset neonatal sepsis in VLBW infants in comparison to the modified values as suggested in the adult population