Assessment of salivary flow rate: Biologic variation and measure error

Objective. To investigate the applicability of the swab method in the measurement of salivary flow rate in multiple-handicap drooling children. To quantify the measurement error of the procedure and the biologic variation in the population. Study Design: Cohort study. Methods. In a repeated measurements design, a baseline series of salivary flow rates were obtained from 45 children. The within-subject SD (SW) was calculated to express the measurements error according to a procedure introduced by Bland and Altman. Results: Two hundred twenty-four samples (mean 0.40 mL/min, SD 0.19 mL/min) were obtained and analyzed. The results of this study indicate that consistent scores were obtained at subsequent measurements, and good parity existed between the two measurements of salivary flow rate at each session. The SW could be estimated (0.11 mL/min), which was applied to quantify the specific variation of the salivary flow rate in our population. Conclusion. According to Bland and Altman, the SW, which is a quantification of the measurement error and biologic variation, was found to be a useful tool to evaluate the obtained baseline salivary flow rate measurements. The swab method can be used to evaluate salivary flow rates in drooling children with cerebral palsy during interventional studies that aim to reduce saliva production.