The effect of age on DNA concentration from whole saliva: implications for the standard isolation method.

Abstract

Adequate quantity and quality of the DNA isolated from saliva samples are crucial for ensuring successful genotyping rates in genetic studies. However, there is little information about these issues when saliva samples are collected from children. The objectives of this study were to assess whether there are differences in DNA quality or quantity isolated from saliva samples of children at different ages and adolescents compared to adults and, if so, to establish a modified protocol to improve and standardize DNA isolation from saliva samples of children. Saliva samples were collected with Oragene DNA Sample Collection Kit from 41 healthy subjects including children of different ages, adolescents, and adults. Quantity and quality of isolated DNA were determined spectrophotometrically. DNA concentration and age were positively correlated (r = 0.676, P < 0.001). A high percentage of samples from children below 12 years yielded DNA concentrations <100 ng/µL and DNA quality a260/a280 ratios of <1.8. Modifying the standard DNA isolation method raised DNA quantity and quality in these critical samples. Age determines, at least in part, the high variability observed in the concentration of DNA isolated from saliva samples. This fact should be taken into account for a better standardization of the DNA isolation to ensure DNA banking in large-scale genetic studies involving children.