Test : Nitro-blue Tetrazolium Test/ NBT Test/ Tertazolium Reduction Test
Indications : Diagnose Chronic Granulomatous Disease (CGD) of childhood.
Physiology : NBT test is used mainly for the diagnosis of chronic granulomatous disease; an X linked inherited disease, characterized by disabled phagocyte NADPH oxidase with inability to efficiently kill phagocytized bacteria. The CGD may result from genetic defects in atleast four different components of the multicompotent NADPH oxidase system.
Normal Range : 2% to 8% segmented neutrophils reduce dye.
Interpretation : This test is a reliable aid in the diagnosis of chronic granulomatous disease in which neutrophils are unable to reduce the dye. In patients with CGD, the NADPH oxidase system fails to generate Superoxide and related oxygen intermediates with resultant susceptibility to recurrent bacterial and fungal infections. Treatment of CGD patients with recombinant interferon –γ has been shown to result in an near normal level of Superoxide production and return of granulocyte bactericidal capacity to normal control levels. Interferon-γ stimulates progenitor cells and their mature progeny.
Test Method : Chronic granulomatous disease can now be diagnosed using restriction fragment length polymorphism with labelled gene probes. The abnormal gene located on the short arm of the X chromosome codes for cytochrome b558.
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