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Abstract
Objective: The neutrophil respiratory burst is crucial for the ability of the host to kill ingested microorganisms. The detection of this activity is an essential part of the laboratory investigation of patients with suspected chronic granulomatous disease (CGD). In this study the traditional qualitative nitroblue tetrazolium (NBT) slide test was compared with a quantitative whole blood dihydrorhodamine 123 (DHR 123) assay using flow cytometry.
Methods: A total of 20 samples submitted to Labplus at Auckland Hospital were screened for CGD by both the NBT and the DHR 123 assays.
Results: While the NBT method was able to demonstrate reduced NADPH oxidase in CGD patients, it is highly subjective and cannot identify carrier states of X-linked-type CGD. In contrast, the quantitative whole blood dihydrorhodamine 123 (DHR 123) flow cytometric method evaluated in this study was more rapid, allowing the proportion of affected cells to be determined, and was able to identify the carrier state of X-linked CGD.
Conclusions: The DHR 123 assay proved to be a more sensitive and more convenient method for the measurement of neutrophil oxidative burst activity and showed a number of advantages over the qualitative NBT slide test for the diagnosis of CGD.
Key words: chronic granulomatous disease, nitroblue tetrazolium slide test, dihydrorhodamine 123, flow cytometry, neutrophil respiratory burst
Ν Z J Med Lab Sci 2013; 67: 45-51
Introduction
Polymorphonuclear neutrophils (PMNs) destroy microorganisms by producing reactive oxygen species (ROS) during the respiratory burst, a normal host defence mechanism that controls infections. The process is controlled by the multicomponent enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, with the production of reactive oxygen species with the formation of superoxide anion (02") (1 ). Intracellular^ the 02" is converted by superoxide dismutase (SOD) to oxygen and hydrogen peroxide (H202), with the latter converted by myeloperoxidase (MPO) to hypochlorous acid and chloramines inside the phagolysosome. These toxic products of the oxidative burst are a part of the powerful 02 -dependent antimicrobial system of PMNs (1, 2).
The clinical implication for impaired function of cellular NADPH oxidase, can be seen in patients with chronic granulomatous disease (CGD) (1).
In this genetic disorder, neutrophils and monocytes recognise and ingest, but are not able to kill certain microorganisms, because phagocytes fail to generate 02". This...