Neutrophil function tests in children with repeated infections—a preliminary study

Nitroblue tetrazolium (NBT) reduction test and candida avidity test were done in 100 cases of children with repeated infections. Serum IgG, IgA, IgM and C3 levels were also determined to assess the status of humoral immunity. It was seen that in the predominent (85%) group of repeated respiratory tract infections, 87 percent and 70 percent had moderate and marked rise of serum IgG and IgM, respectively, though 59 percent had lower than normal IgA values. C3 levels were normal in 41 percent and decreased in 36 percent in the same group. NBT was decreased in 45 percent within normal range in 30 percent and increased in 25 percent. The Candida avidity index (CAI) was decreased in 90 percent of cases with respiratory tract infections. The observations in the other groups were comparable to those of group repeated respiratory infections. As many of the cases were malnourished the influence of malnutrition on phagocytic activity could not be ruled out. There was no correlation between NBT and CAI tests and the levels of serum immunoglobulins and C3. The CAI appears to be more sensitive than NBT, indicating the particle avidity of the neutrophils.