Decreased neutrophil oxidative burst Reduced reactive oxygen species production in neutrophils HP:0003203 HP:0025632 Decreased oxidative burst The NBT test measures the ability of neutrophils to convert nitroblue tetrazolium (NBT), to a deep blue color. This test can be abnormal in chronic granulomatous disease. An abnormal test result implies a reduction in the ability of neutrophils to kill bacteria. Polymorphonuclear neutrophils comprise more than 60% of the circulating white blood cells in humans. They have a central role in innate immunity and they regulate adaptive immunity. In healthy individuals, circulating neutrophils are freely flowing in a resting, dormant state. Upon infection, neutrophils are the first circulating cells to arrive at the infection and inflammatory site. Phagocytosis triggers the activation program of the neutrophils, leading to the intraphagosomal release of antibacterial peptides, proteases, myeloperoxidase, and superoxide anion (O2-), which is produced via the activation of the NADPH oxidase. Superoxide anion is the initiating spark leading to the generation of reactive oxygen species (ROS), i.e., hydrogen peroxide (H2O2), hydroxylradical and hypochlorous acid (HOCl), all contributing to the death and destruction of the bacteria within the phagosome. ROS production by the phagocytes was first referred as the respiratory burst or oxidative burst due to the rapid and cyanide-insensitive increase in oxygen uptake, increase in glucose consumption, andimmediate ROS release. The enzyme system dedicated to superoxide anion production, i.e., the phagocyte NADPH oxidase, a member of the NOX family of proteins also referred as NOX2, is composed of six proteins, two trans-membrane proteins (p22phox and gp91phox) that form theflavocytochrome b558, and four soluble proteins (p47phox,p67phox, and p40phox and the small G-proteins, Rac1/2). Negative NBT reduction test Negative nitroblue tetrazolium reduction test HP:0005512 UMLS:C4280805 Abnormal decrease of neutrophil oxidative burst, commonly measured through oxidation of dihydrorhodamine (DHR) using flow cytometry or through nitroblue tetrazolium test (NBT) using optical microscopy, upon stimulation with phorbol-12-myristate-13-acetate (PMA), E. coli or other ligands. Impaired oxidative burst Abnormal neutrophil physiology