61 4 100 mL Water Swallow Test During the 100 mL WST, a subject was asked to drink 100 mL of water as quickly as is comfortably possible. The time to swallow this 100 mL (in seconds) and the number of swallows were counted. The researcher counted the number of swallows by touching the larynx, and the subject was asked to count the number of swallows simultaneously, as a control reference. Timing started when the water touched the bottom lip, and stopped when the larynx came to rest after the last swallow.14 From these measurements, the following parameters could be calculated: the swallowing volume (the amount of mL per swallow), the swallowing capacity (the amount of mL per second) and the swallowing speed (the time per swallow). Swallowing volume was calculated by dividing the number of mL by the number of swallows. Swallowing capacity was calculated by dividing the number of mL by the duration. Swallowing speed was calculated by dividing the duration by the number of swallows. Subjects failed the test when they coughed or choked post swallow, had a wet voice quality post swallow, or were unable to drink the whole 100 mL.11 When a person was unable to drink the 100 mL, the residual water was measured and noted. Subjects were instructed to perform the WST two times, with an interim period between 15 minutes and two hours, with the same rater and testing conditions for all subjects. Statistical analyses Test-retest reproducibility of the WST outcomes was tested by a two-way random, single measurement, absolute agreement, intra class correlation coefficient (ICC2,1) calculated as , in which MSR = mean square of rows; MSE = mean square for error; MSC = mean square for columns; k = number of measurements; and n = number of subjects. Cut-off points for the ICC were chosen as poor (<0.5), moderate (0.5 to 0.75), good (0.75 to 0.90), and excellent (>0.90).21,22 The Standard Error of Measurement (SEM) was calculated as .23 For the SD, the Standard Deviation of the difference between the two WSTs was used. The SEM percent change (SEM%) was calculated as , in which = the mean of all measurements of test and retest. The Smallest Detectable Change (SDC) was calculated as !"# $ .24,25 The SDC percent change (SDC%) was calculated as % , in which = the mean of all measurements of test and retest. In order to check for systematic bias, variability and agreement, Bland-Altman plots were constructed by plotting the test-retest difference versus the mean value of the test and retest. The agreement between the two tests was summarized using the mean difference and SD of the difference, and the 95% Limits of Agreement (LoA) were calculated as &'( ) !"# .26

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