Neutrophil function test: comparison between Conventional Nitroblue Tetrazolium (NBT) and direct NBT assays / Nurain Zulaika Mohd Noor

Polymorphonuclear neutrophils (PMNs) are white blood cells that play an important role as the first line of immune defence against pathogens. Neutrophils activation will trigger production of oxidative burst which is mediated by NADPH oxidase. The product of oxidative burst is a part of the powerful bacteria killing system in PMNs. Neutrophils function is evaluated based on its ability to produce oxidative burst. The conventional nitroblue tetrazolium (NBT) assay is the gold standard method to evaluate neutrophils function. The NBT test is however laborious, complicated and skill-dependent. An alternative method called direct NBT assay was recently introduced. Thus, in the present study, the performance between conventional and direct NBT assays were compared. A total of 20 heparinized venous blood samples from normal individuals and one sample from chronic myeloid leukaemia (CML) patient were evaluated for neutrophil function by using both methods. There was a good correlation between conventional and direct NBT assays for percentage ofNBT positive cell with PMA stimulated cells (rs=0.97, P<O.OI) and unstimulated cells (rs=0.93, P<O.OI). Hence, the results from direct NBT assay is as comparable as that of conventional NBT assay. The direct NBT assay is quicker and simpler than the conventional NBT assay because whole blood is used thus it eliminates the preparation ofPMNs cell. In addition, sample volume of as small as 0.1 ml blood can be used which makes the direct NBT assay ideal for evaluation of neutrophil function in children and neonates. Therefore, the direct NBT assay may be a better choice or an alternative approach to evaluate neutrophil function as it is quicker, simpler, easier and less skill needed.