High light scatter by neutrophils in the Bayer-Technicon H*2 analyzer: a screening test of morphologically defective responsiveness to in vitro chemotactic stimulation

The Bayer-Technicon H*2 haematological analyser provides differential white blood cell count, including the assay of polymorphonuclear leukocytes by light scattering and the absorbance increase following the cytochemical reaction for myeloperoxidase. The mean value of polymorphonuclear leukocytes scatter, which reflects polymorphonuclear leukocytes volume, is printed in a separate report "for laboratory use only" as a ybar value in arbitrary units. In certain patients neutrophils displayed an unreported correlation between polymorphonuclear leukocytes high ybar basal values (> or = 37.00 arbitrary units) (determined on the H*2) and a defective response in vitro to the chemoattractant, formyl-methionyl-leucyl-phenylalanine (determined by microscopic evaluation of polymorphonuclear leukocytes shape change (polarization)). The patients showing no polymorphonuclear leukocyte response or a defective one to formyl-methionyl-leucyl-phenylalanine were all affected by "Systemic Inflammatory Response Syndrome (SIRS)". Therefore 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-dependent deactivation of endotoxin or lipopolysaccharide-pretreated polymorphonuclear leukocytes, the "normal" response to formyl-methionyl-leucyl-phenylalanine of the "false negative" cases may occur because the endotoxaemia in these patients is too low to prevent it.(ABSTRACT TRUNCATED AT 250 WORDS)