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

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.