Test-retest and inter-rater reliability of a method to measure wrist and finger spasticity

To describe the reliability of an instrument (Neuro- Flexor) designed to be used in the clinic for quantification of the relative contribution of spasticity, elasticity and viscosity to resistance during passive wrist movements. A test-retest and inter-rater reliability study. A convenience sample of 34 adults with chronic stroke with spasticity in the hand, and a reference group of 10 healthy persons. Two raters assessed the participants with the NeuroFlexor. Elastic, viscous and neural components of passive movement resistance were quantified at the wrist. Test-retest and inter-rater intraclass correlation coefficient (ICC2.1) were calculated for each component for both raters and two sessions. Degree of measurement error was evaluated using the coefficient of variation and the repeatability coefficient. Reliability was high for the neural component (test-retest: 0.90-0.96; inter-rater: 0.90-0.94), fair to good for the elastic component (test-retest: 0.79-0.88; inter-rater: 0.76-0.76), and fair to high for the viscous component (test-retest: 0.88-0.90; inter-rater: 0.75-0.80). Based on test-retest data, the coefficients of variation for the neural, elastic and viscous components were 25%, 26% and 16%, respectively, and the repeatability coefficients were 1.798, 1.897 and 1.404, respectively. The NeuroFlexor instrument is a reliable measure of spasticity and of muscle elasticity and viscosity in individuals with wrist and finger muscle resistance to passive stretch after stroke.