Evaluation of a new clinical test protocol for pointing acuity - An initial validity study

Sensorimotor control of the arm and hand can be disturbed in various health conditions causing deviant and unfavourable movement patterns. This study aimed to evaluate a new clinical test protocol for pointing acuity using the Leap Motion Controller (LMC) and assess the concurrent validity against a standard laboratory motion capture system (Qualisys Motion Capture, QMC). Twenty participants (mean age 44.4 years) performed the pointing acuity tests with eyes open and closed, and with left and right hand. Outcome measure was the mean absolute error (AE) in millimeters (mm) of 10 trials. Pearson's r or Spearman's rho were used to analyse the correlations between LMC and QMC, and Bland-Altman were used to analyse the agreement. There were moderate to very strong correlations (r: 0.67 to 0.95) between LMC and QMC in tests with eyes closed. In contrast, tests with eyes open showed weak correlations; rho 0.27 for both left and right hand. Bland-Altman showed median bias of ≤ 1.4 mm (LoA 0.1 to 17.5 mm) between LMC and QMC with eyes open, and ≤ 5.1 mm (LoA -31.6 to 21.5 mm) with eyes closed. Assessing pointing acuity using LMC with a standardized test protocol has an acceptable concurrent validity when compared to a 3D-based multi camera system (QMC), supporting its potential use in clinical settings. Future research should evaluate its psychometric properties regarding discriminative validity, reliability and responsiveness in various populations.