Comparing automated vs manual leukocyte differential counts for quantifying the 'left shift' in the blood of neonates

Abstract

Objective: 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.