Thesis Title

An Investigation of the Concurrent Validity of Line-Spread Testing in Measuring the Viscosity of Thickened Liquids


Alisa Johnson

Date of Graduation

Spring 2006


Master of Science in Communication Sciences and Disorders


Communication Sciences and Disorders

Committee Chair

Lynette Goldberg


The literature is replete with clinical measures used to assess the viscosity of thickened liquids, e.g. spoon-drip test, funnel test, pour test, and mouth-feel test, and the problems inherent in using subjective interpretation of these measurement methods. Objective measurement and interpretation is recommended for the safe and effective treatment of persons with dysphagia (swallowing difficulties). The line-spread test has been suggested as an objective and clinically useful measure of the viscosity of thickened liquids. However, few data exist to document the concurrent validity of this measurement method in comparison to the documented objectivity of viscometer measurement. In the current study, four thickening agents were mixed with bottled water to a nectar-like consistency. Viscosity of the thickened water was measured using line-spread testing and viscometry. Results documented a statistically significant correlation between line-spread and viscometer measurement for two of the four thickening agents: Thick-It and Thick & Easy. However, the actual strength of the correlations, measured using r2 (index of determination), was low. These preliminary results suggest that line-spread testing appears worthy of continued investigation to explore its measurement of all properties of liquid flow. Clinicians currently using line-spread testing need to develop a consistent technique that includes the rapid removal of the cylinder to minimize error.


dysphagia, viscosity, line-spread test, viscometer measurement, index of determination

Subject Categories

Communication Sciences and Disorders


© Alisa Johnson