There are significant differences in white blood cell (WBC) total and differential counts between newborns and older children. Alterations in WBC total and differential count can be an early sign of infection (leucopenia, leucocytosis, shift to the left). Total WBC counts should be always adjusted for given postnatal age – see Table.
|Parameter||1 day||7 days||30 days|
|Leucocyte (x 109 / l)||9 – 35||5 – 21||5 – 19|
I/T index = ratio of immature forms (promyelocyte, myelocyte, bands) to mature forms of neutrophil granulocytes (normal ratio < 0.2)
① Carr R. Neutrophil production and function in newborn infants. Br J Haematol. 2000;110(1):18-28. doi:10.1046/j.1365-2141.2000.01992.x