This study aimed to evaluate an existing liquid-thickening guideline provided by a major manufacturer of thickener in Hong Kong and to provide directions for the implementation of the IDDSI framework. Fifteen participants who are naïve to liquid thickening were required to prepare thickened liquids samples from three drink bases (i.e., Milk-tea, Chinese tea, and Herbal tea) at two target consistency levels (i.e., mildly and medium/moderately thick) based on two guidelines (i.e., the manufacturer's guideline and an IDDSI-driven guideline). Viscosities of the samples were measured rheologically to reflect liquid consistency. The manufacturer's guideline resulted in distinguishable viscosities at the two consistency levels (F(1, 35.464) = 113.764, p < 0.001, ηp2 = 0.802), as well as different viscosities in different drink bases (F(1.267, 35.464 = 92.951, p < 0.001, ηp2 = 0.769). Comparison between the manufacturer's and the IDDSI-driven guideline showed that the later resulted in more viscous liquid samples in all drink bases and at both consistency levels. The difference between the two guidelines was statistically significant (F(1,28) = 35.137, p < 0.001, ηp2 = 0.557). Following only the manufacturer's guideline when thickening non-water beverages may lead to discrepancy between the resultant and prescribed consistencies. Thus, it should be considered inadequate to ensure swallowing safety. The effect of drink base should be emphasized to patients and caregivers, and pre-serving tests should be introduced. Despite similar classifications and terminologies used between the current local framework and the IDDSI framework, measures should be taken to avoid potential confusions and associated threats to swallowing safety.
Keywords: Deglutition disorders; Dysphagia; IDDSI; Liquid-thickening guidelines; Non-water local beverages; Viscosity.