The NBT test is dependent upon the microscopic evaluation of stained neutrophils for the presence of intracellular formazan.
The NBT test involves the microscopic assessment of the ability of patient neutrophils to reduce the yellow soluble redox dye NBT to form blue-black formazan, an insoluble material that precipitates intracellularly.
Complement was used as opsonin for the NBT test and was provided using fresh pooled human serum.
The activity of neutrophils in the NBT test depends upon the ability of the cells to both adhere to glass and to produce oxidative radicals.
The results of the NBT test showed sixteen patients with normal results; however, the presence of a carrier state could not be excluded by this method on these samples.
Other advantages of the DHR assay over the NBT test include its ability to more clearly identify CGD patients and to establish the carrier state of the X-linked forms of the condition.
Both methods measured the ability of neutrophils to mount a neutrophil respiratory burst and results of the NBT test and those from the DHR fluorescence test showed good correlation.
The NBT test (14) measures the percentage of actively phagocytosing (positively stained) neutrophils in blood smears.
A blood sample was used for the NBT test (14) in which 400 neutrophils from a blood smear were observed under 400x magnification to determine the proportion that were positively stained and showed evidence of active involvement in phagocytosis.
This study investigated 3 aspects of plague in its natural hosts in one of the world's major plague foci: the effect of infection on host survival, the dynamics of the antibody response to infection, and the specificity of the NBT test, which has been used as a measure of rodent infection status in previous studies.
Values in the NBT test, which may be an indication of the proportion of neutrophils actively involved in phagocytosis, especially during acute bacterial infections (15), have been used in some studies to classify animals positive for antibody to Y.