Background: Standardization in collection and testing of oral fluid is lacking.
Methods: A novel standardized collection and quantification system for oral fluid testing was evaluated. Sample collection volumes were determined. For determination of the saliva content in oral fluid samples, tartrazine, which is an integral part of the saliva extraction solution serving as an internal standard, was used. Results were compared with those obtained by employing glucose as a 'supplemental internal standard' for determination. Analytical performance of the new system for collection and quantification of oral fluid was evaluated. Calcium and magnesium analyte concentrations in oral fluid samples were measured with a routine laboratory method and compared to a reference method.
Results: Volumes of oral fluid samples collected ranged from 4.9 to 10.5 mL. The mean saliva content in oral fluid samples was found to be 65.5 percent by volume (vol.-%) when determined through the tartrazine concentration and 65.0 vol.-% when determined through the glucose concentration. Evaluation of analytical performance revealed interassay imprecision coefficients of variation (CVs) ranging from 1.5% to 3.2% and intraassay imprecision CVs from 1.1% to 2.5%. When linearity was tested, a quasi-linear curve was observed (R2=0.99). Comparison of two different methods for determination of calcium and magnesium concentrations showed correlations of R2=0.96 for calcium and R2=0.97 for magnesium.
Conclusions: The new system for collection and quantification of oral fluid helps to improve standardization of pre-analytics in oral fluid testing and to provide reliable and accurate quantification of analytes in oral fluid samples.