The neutrophil ‘left shift’ can be measured via the immature to total (I/T) neutrophil ratio or the absolute bands per μl using a manual differential count. It can also be measured from an automated differential count by the immature granulocyte percentage (IG%) or the absolute IG per μl. In neonates, it is unknown if the manual or automated differential count is superior.STUDY DESIGN:
We directly compared complete blood counts (CBCs) with manual and automated differential counts from infants < 90 days old, and documented whether or not each neonate was infected. We developed reference intervals for I/T ratio, bands per μl, IG% and IG per μl using values from non-infected neonates.RESULTS:
The database had 10 714 CBCs. The upper reference interval for I/T ratio was 0.29 in the first 48 h and 0.31 thereafter; bands per μl was 3710 μl- 1 in the first 48 h and 1785 μl- 1 thereafter. IG% was 6.2% then 4.2%; IG per μl was 1460 μl- 1 then 613 μl- 1. Statistical performances of the four methods were equivalent for identifying infection.CONCLUSIONS:
We developed reference intervals for four methods of quantifying a neonate's ‘left shift’. The information from automated differentials is not inferior to that from manual differentials in identifying infections, but automated differentials have the advantages of a larger sample size, being less expensive, and faster performance times.