Concurrent validity and test-retest reliability of the Virtual Peg Insertion Test to quantify upper limb function in patients with chronic stroke

Background: Measuring arm and hand function of the affected side is vital in stroke rehabilitation. Therefore, the Virtual Peg Insertion Test (VPIT), an assessment combining virtual reality and haptic feedback during a goal-oriented task derived from the Nine Hole Peg Test (NHPT), was developed. This study aimed to evaluate (1) the concurrent validity of key outcome measures of the VPIT, namely the execution time and the number of dropped pegs, with the NHPT and Box and Block Test (BBT), and (2) the test-retest-reliability of these parameters together with the VPIT's additional kinetic and kinematic parameters in patients with chronic stroke. The three tests were administered on 31 chronic patients with stroke in one session (concurrent validity), and the VPIT was retested in a second session 3-7 days later (test-retest reliability). Spearman rank correlation coefficients (rho) were calculated for assessing concurrent validity, and intraclass correlation coefficients (ICCs) were used to determine relative reliability. Bland-Altman plots were drawn and the smallest detectable difference (SDD) was calculated to examine absolute reliability. Results: For the 31 included patients, 11 were able to perform the VPIT solely via use of their affected arm, whereas 20 patients also had to utilize support from their unaffected arm. For n = 31, the VPIT showed low correlations with the NHPT (rho = 0.31 for time (T-ex[s]); rho = 0.21 for number of dropped pegs (N-dp)) and BBT (rho = -0.23 for number of transported cubes (N-tc); rho = -0.12 for number of dropped cubes (N-dc)). The test-retest reliability for the parameters Tex[s], mean grasping force (F(g)go[N]), number of zero-crossings (N(zc[1/s)go/return) and mean collision force (F-cmean[N]) were good to high, with ICCs ranging from 0.83 to 0.94. Fair reliability could be found for F(g)return (ICC = 0.75) and trajectory error (E(traj)go[cm]) (0.70). Poor reliability was measured for E(traj)return[cm] (0.67) and N-dp (0.58). The SDDs were: T-ex = 70.2 s, N-dp = 0.4 pegs; F(g)go/return = 3.5/1.2 Newton; N(zc[1/s])go/return = 0.2/1.8 zero-crossings; E(traj)go/return = 3.5/1.2 Newton; N(zc[1/s])go/return = 0.2/1.8 zero-crossings; E(traj)go/return = 0.5/0.8 cm; F-cmean = 0.7 Newton. Conclusions: The VPIT is a promising upper limb function assessment for patients with stroke requiring other components of upper limb motor performance than the NHPT and BBT. The high intra-subject variation indicated that it is a demanding test for this stroke sample, which necessitates a thorough introduction to this assessment. Once familiar, the VPIT provides more objective and comprehensive measurements of upper limb function than conventional, non-computerized hand assessments.