The nitroblue tetrazolium (NBT) test and white blood cell count in acute throat infections

The clinical value of the NBT test and of leucocyte counts in the aetiological differentiation of acute throat infections was investigated. In our hands a frequency of less than 13% NBT positive neutrophils is considered as normal and a test value above 19% as "positive", i.e. indicating a bacterial infection. More than 19% or more than 1 800 NBT positive neutrophils per mm-3 blood were found in 10 of 18 patients with an infection caused by beta-haemolytic streptococci, in 1 of 2 patients with a Mycoplasma pneumoniae infection and in 1 patient with both a streptococcal and mycoplasmal infection, but in none of 19 patients with a viral infection. Since 8 of 18 patients with streptococcal throat infection had normal NBT test results, the NBT test apparently is of limited value in the early recognition of these infections. A high NBT test value would however support the diagnosis. The white blood cell and neutrophil counts were of little value in the differentiation between streptococcal and viral throat infection.