HIGH LIGHT SCATTER BY NEUTROPHILS IN THE BAYER-TECHNICON H-ASTERISK-2ANALYZER - A SCREENING-TEST OF MORPHOLOGICALLY DEFECTIVE RESPONSIVENESS TO IN-VITRO CHEMOTACTIC STIMULATION

The Bayer-Technicon H2 haematological analyser provides differential white blood cell count, including the assay of polymorphonuclear leuko cytes by light scattering and the absorbance increase following the cy tochemical reaction for myeloperoxidase. The mean value of polymorphon uclear leukocytes scatter, which reflects polymorphonuclear leukocytes volume, is printed in a separate report ''for laboratory use only'' a s a ybar value in, arbitrary units. In certain patients neutrophils di splayed an unreported correlation between polymorphonuclear leukocytes high ybar basal values (greater than or equal to 37.00 arbitrary unit s) (determined on the H2) and a defective response in vitro to the ch emoattractant, formyl-methionyl-leucyl-phenylalanine (determined by mi croscopic evaluation of polymorphonuclear leukocytes shape change (pol arization)). The patients showing no polymorphonuclear leukocyte respo nse or a defective one to formyl-methionyl-leucyl-phenylalanine were a ll affected by ''Systemic Inflammatory Response Syndrome (SIRS)''. The refore the predictive value of the positive test for SIRS is 100%. On the other hand 8.8% of SIRS patients had polymorphonuclear leukocytes < 37.00 arbitrary units of ybar basal value and a ''normal'' response to formyl-methionyl-leucyl-phenylalanine; the predictive value of the negative test being 90%. Since we demonstrated in vitro a dose-depende nt deactivation of endotoxin or lipopolysaccharide-pretreated polymorp honuclear leukocytes, the ''normal'' response to formyl-methionyl-leuc yl-phenylalanine of the ''false negative'' cases may occur because the endotoxaemia in these patients is too low to prevent it. Thus, high p olymorphonuclear leukocyte scatter values on the H2 allows the identi fication of a group of critically ill patients in whom activated neutr ophils do not respond to further stimulation by polymorphonuclear leuk ocyte polarization, a shape change that is characteristic of migrating cells and essential for chemotaxis.