Validation of a new strength measurement device for amyotrophic lateral sclerosis clinical trials

Introduction: Strength measures with reduced variability and higher sensitivity could improve efficiency in clinical trials of amyotrophic lateral sclerosis (ALS). The Accurate Test of Limb Isometric Strength (ATLIS) was developed to precisely and conveniently measure force in 12 muscle groups. In this study we evaluate the reliability and validity of the ATLIS testing protocol. Methods: Twenty healthy adults and 10 patients with ALS were tested twice by the same or by different evaluators to determine test-retest and interrater reliability. Twenty healthy adults were examined using ATLIS and a wellvalidated strength testing protocol (TQNE) to assess criterionbased validity. Results: Mean absolute variation between tests was 8.6%, and intraclass correlation coefficients for each muscle group were high (range 0.82-0.99). The Pearson correlation coefficient of mean ATLIS and TQNE scores was 0.90. A subject survey demonstrated high user acceptance of ATLIS. Conclusions: ATLIS is convenient for patients and evaluators, produces precise strength measurements, and is easily moved between examining rooms.