Reliability and validity of the Duncan-Ely test for assessing rectus femoris spasticity in patients with cerebral palsy

Abstract

Aim: The aim of this study was to clarify the method of the Duncan-Ely test and to estimate its interobserver reliability and validity by comparing it with three-dimensional gait analysis (3DGA). Method: This study included 36 consecutive ambulatory patients with cerebral palsy (CP) who underwent preoperative 3DGA. The Duncan-Ely test was performed during three different velocities (slow, gravity, and fast). The interobserver reliability was assessed by three examiners. The results of the test were compared with kinematic variables derived from the gait analysis to assess the sensitivity and specificity of the test. The cut-off value was determined at the point of trade-off between the highest sensitivity and specificity. Results: The intraclass correlation coefficient measuring interobserver reliability of the Duncan-Ely test was greatest during fast velocity (0.819). The sensitivity and specificity of the test during gravity velocity for knee range of motion total were 63.0% and 100% respectively, with a cut-off value of 78.3°. The sensitivity and specificity of the test during fast velocity for knee range of motion total were 66.7% and 100% respectively, with a cut-off value of 65. Interpretation: The Duncan-Ely test shows excellent reliability in fast knee-flexion velocity, and good sensitivity and specificity compared with 3DGA during physical examination as a preoperative assessment of rectus femoris spasticity in patients with CP. What this paper adds: The interobserver reliability of the Duncan-Ely test was greatest during fast velocity. The sensitivity and specificity of the Duncan-Ely test were greatest during fast velocity. This article is commented on by Stott on pages 895-896 of this issue.