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.