The variability of immunoglobulins and albumin in salivary secretions of children.

The variation of concentrations of immunoglobulins and albumin in consecutive daily collections of saliva was studied in 33 infants, aged 6 months to 5 years, for periods ranging from 16 to 26 days. The concentration and the within-child variability of IgA and albumin and the detection of IgG and IgM in saliva increased with age. Between-child variances were greater than the within-child variances by a factor of 2.8 for log (IgA) and 1.3 for log (albumin). The geometric mean IgA levels were consistently higher and IgG was detected more frequently during upper respiratory tract infections compared with periods of non-infection. There were no changes in albumin levels between infection and non-infection periods, suggesting a local immune response rather than serum leakage. There were significant within-child correlations (autocorrelations) between levels of IgA in saliva collected on consecutive days and samples collected up to 3 days apart. The autocorrelations between levels of albumin were significant for samples collected up to 2 days apart. The autocorrelation for IgA was significantly greater during infection periods compared with non-infection periods for samples collected on consecutive days.