The nitroblue tetrazolium reduction test in canine leishmaniasis

The nitroblue tetrazolium reduction test (NBT) is a quick, easy and cheap assay based on the activation percentage of neutrophils in peripheral blood. The aim of this study was to evaluate the NBT on healthy dogs and in dogs affected by different degrees of leishmaniasis (Stages I and IV). Forty healthy dogs, 20 dogs in Stage I and 20 dogs in Stage IV were included in the study. Three millilitres of blood were extracted from all the dogs via jugular venipuncture in tubes with EDTA. Incubation with NBT was performed depositing 0.05 ml of the leukocyte suspension in the same quantity of 0.1% concentration NBT. The results of the test were reported as NBT reduction rate which represents the percentage of the total of neutrophils evaluated that presented cytoplasmatic accumulations of formazan, meaning a positive NBT reduction. The mean NBT reduction rate for the healthy dogs group was 4.57%, 34% for Stage I dogs (mild disease) and 3.7% for dogs in Stage IV (severe disease), showing that dogs affected with leishmaniasis but with no clinical development of disease have a significantly higher neutrophil reactivity (p<0.01). Although more studies evaluating the correlation of NBT with other tests prior to and during treatment are needed, NBT could be a good assay in canine leishmaniasis evaluation.