J Korean Dysphagia Soc.  2014 Jan;4(1):18-22.

Fork Test: A New Simple and Reliable Viscosity Measurement for Dysphagia Diet

  • 1Department of Physical Medicine and Rehabilitation, Dongguk University Ilsan Hospital, Dongguk University College of Medicine, Goyang, Korea
  • 2Department of Food and Nutrition Service, Dongguk University Ilsan Hospital, Goyang, Korea


To develop and validate a simple and reliable viscosity assessment tool, the fork test, for dysphagia diet. Fork test is based on the flow of the food between the fork’s tines and the food that remains on the fork. Method: 27 kinds of viscosity-altering water and thickener mixtures were prepared and their viscosities were measured by a viscometer and compared to those by the fork test to evaluate the correlation between the two. Nine kinds of viscosity-altering formulations of dysphagia diet were selected and classified using the fork test. Interobserver reliability of the fork test was assessed using an intraclass correlation coefficient (ICC). Result: Water and thickener mixtures were categorized into grade 3, grade 2 or grade 1 according to the fork test, using reference values of 0 to 300 cP, 300 to 10000 cP and more than 10000 cP by the viscometer. Mayonnaise, mango pudding and mashed boiled pumpkin were classified as grade 1. Curd type yogurt, honey and tomato ketchup were classified as grade 2 and tomato juice, fluid type yogurt and diluted barium solution as grade 3. The fork test showed excellent interobserver reliability (ICC=0.994).
The fork test demonstrated good reliability and validity. It can be used as a practical tool to assess viscosity and classify dysphagia diet.


Dysphagia; Treatment; Viscosity; Deglutition
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