nitroblue tetrazolium assay - (Oct/11/2011 )

Has anyone undertaken nitroblue tetrazolium assay ?

If so any tips would be greatly appreciated.

UTIs-screening tests : to screen UTIs we use NBT reduction test, add 80 μl of 0.75 mM NBT, 110 μl of 20 mM Hepes buffer, pH 7.4, and 10 μl of 10% Triton X-100 to 200 μl of fresh whole urine at room temperature and incubate for three minutes. A positive NBT result is a color change to blue-violet.