Improved automated differential counts of leukocytes from newborn infants using pre-dilution of blood samples.

A method for automated differential leukocyte counting using peroxidase staining and light scatter (H1) failed to present results in more than 25% of blood samples from newborn infants. These failures were mostly seen at or below 2 weeks of age, and with high concentrations of haemoglobin F (HbF). Dilution of the blood with equal amounts of isotonic saline made the problem disappear almost completely. The results of differential counts on such diluted blood samples also compared more favourably with traditional manual counts of blood smears than did the results obtained with undiluted blood. The present method with blood diluted 1/2 is therefore recommended for routine use in newborn infants.