Which of the following tests would be most beneficial in the diagnosis of a patient suspected of having chronic granulomatous disease of childhood?

Patients with the chronic granulomatous disease, a sex-linked recessive disease, are deficient in phagocyte function. The neutrophils/ monocytes lack reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, a critical enzyme that is needed for the production of reactive oxygen intermediates (ROIs) responsible for the respiratory burst. Nitroblue tetrazolium (NBT) is a pale yellow dye that accepts H+ and is reduced as a result of NADPH oxidation to a blue intracellular precipitate. In the NBT test, peripheral blood neutrophils take up the dye after a stimulus (latex beads or other paicles). Failure of the cells to reduce the NBT dye to a blue color is consistent with a diagnosis of chronic granulomatous disease.E rosette-formation is a historically impoant assay for identification of human lymphocytes. T cells have a receptor (CO2) by which they are able to bind sheep erythrocytes (E). A lymphocyte with several erythrocytes attached to it has the appearance of a rosette.