Methods for the assessment of neutrophil function during extracorporeal circulation

Many different assays and test systems have been used to study the effects of biocompatibility on neutrophil function in haemodialysis patients. This review examines the most common and recommends three assays that are widely available, amenable to standardization, and minimally susceptible to artefacts. The recommended assays are neutrophil count, plasma concentrations of the elastase- alpha 1-proteinase inhibitor complex (a measure of neutrophil degranulation), and, the neutrophil oxidative burst response as measured by the reduction of ferricytochrome-c by superoxide or the oxidation of dihydrorhodamine 123 by hydrogen peroxide. This review also discusses the advantages and disadvantages of using whole blood or isolated cell assays and the choice of in-vitro, on-line, or clinical dialysis test systems. While whole blood assays are associated with fewer artefacts than those using isolated cells, specialized equipment is needed to study neutrophils and some questions concerning localization of defects in neutrophil function can only be addressed in isolated cells. For these reasons a role for isolated cell assays continues. For similar reasons there remains a role for in-vitro and on-line test systems, even though clinical dialysis studies are preferred whenever possible.