Comparison of two methods for the diagnosis of chronic granulomatous disease - neutrophil oxidative burst measured by the nitroblue tetrazolium slide test versus the dihydrorhodamine 123 flow cytometric assay

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.