Neutrophil mean peroxidase: a biologically interesting parameter with a potential for WBC differential quality control.

This study has shown the neutrophil mean peroxidase measurement on the Technicon H6000 to be a simple reproducible technique for measuring neutrophil myeloperoxidase. This measurement shows no interference from contaminating eosinophils unlike spectrophotometric methods. The WBC count had little effect on the CV of the neutrophil mean peroxidase within the normal working range of the machine. Variations in the hydrogen peroxide concentration of the peroxidase substrate also had little effect on this measurement. Haemoglobin however had a significant inhibitory effect on the neutrophil mean peroxidase but this was in a predictable manner. The same inhibition of peroxidase also caused a decrease in the eosinophil count. This varied between individuals. The method described represents a suitable assay for the detection of varying degrees of neutrophil myeloperoxidase activity including the acquired and hereditary deficiencies. This parameter is potentially useful for the quality control of the cytochemically derived WBC differential.