Routine application of the nitroblue tetrazolium test in the clinical laboratory

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Abstract
A modified nitroblue tetrazolium test (NBT) is described which is suitable for routine application in the haematology or bacteriology laboratory and which provides a rapid aid to the diagnosis of bacterial infection. Hitherto published methods have recommended the use of heparinized whole blood samples for the performance of the NBT test. However, we have demonstrated that the use of the sucrose polymer Ficoll permits the test to be carried out on buffy coats prepared from venous blood anticoagulated in sequestrene (EDTA). The mean percentage of NBT-positive neutrophils in 60 healthy control subjects was 6·1. The mean percentage of NBT-positive neutrophils in 56 patients with confirmed or presumed bacterial infection was 34·2. Scores within the normal range were observed in 13 patients in this group. Forty-eight individuals with viral infection yielded a mean percentage of NBT-positive neutrophils of 8·5. Six patients in this group gave scores above the upper limit of normal. Both pathological groups are described in detail and applications of this test are suggested.