Saccharin test: Methodological validation and systematic review of the literature

Objectives Saccharin test (ST) is a convenient method to assess the efficiency of mucociliary clearance, the primary defense mechanism of the upper airways' tract. The study objectives are to: (1) substantiate its short- (3 days) and long-term (30 days) repeatability; (2) assess its tolerability; (3) conduct a systematic literature review and to compare our results with the existing evidence. Methods Twenty-nine healthy subjects were enrolled in an observational prospective study to perform an ST on three separate visits (at baseline; at follow-up visits at day 3 and at day 30). Transit times were recorded and self-reported nasal and general symptoms noted. A systematic review of the literature was conducted to compare our results with the existing literature. Results The mean values (+/- SD) of ST transit time (STTT) were 7.085 (+/- 2.19), 7.788 (+/- 2.11), and 7.790 (+/- 2.06) minutes at baseline, day 3, and day 30, respectively. Significant linear regression analysis was observed between day 3 and baseline (r = .193; P = .019) and day 30 and baseline (r = .182 P = .024). Significant agreement for the intrasession repeatability was observed with an ICC = .354 (P = .001). Outcomes' comparisons between baseline vs day 3 (P = .197) and baseline vs day 30 (P = .173) were not statistically significant. ST was well tolerated. Concordance with existing literature's data and high level of STTT repeatability were confirmed by the qualitative analysis. Conclusion STTT reproducibility was good both in the short- and long-term. ST tolerability was very good. Our study data are consistent with the existing literature, indicating ST as a sound methodology for detection of early respiratory health changes and for specific regulatory application in respiratory research.