Tip 90: IT ratio

The I:T ratio has the best sensitivity of any of the neutrophil indices.

 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 there is an I:T ratio > 0.2 and low neutrophil count or high CRP, then infection is likely.

References: Polin, R.A., Papile, L.A., Baley, J.E., Bhutani, V.K., Carlo, W.A., Cummings, J., Kumar, P., Tan, R.C., Wang, K.S. and Watterberg, K.L., 2012. Management of neonates with suspected or proven early-onset bacterial sepsis. Pediatrics129(5), pp.1006-1015.

Pilling, E., McLellan, E. (2013). Sepsis – early onset <72 hours of age (neonates). Yorkshire and Humber Neonatal ODN (South) guideline.

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