Does the Finger-to-Nose Test measure upper limb coordination in chronic stroke?

Background: We aimed to kinematically validate that the time to perform the Finger-to-Nose Test (FNT) assesses coordination by determining its construct, convergent and discriminant validity. Methods: Experimental, criterion standard study. Both clinical and experimental evaluations were done at a research facility in a rehabilitation hospital. Forty individuals (20 individuals with chronic stroke and 20 healthy, ageand gender-matched individuals) participated.. Both groups performed two blocks of 10 to-and-fro pointing movements (non-dominant/affected arm) between a sagittal target and the nose (ReachIn, ReachOut) at a self-paced speed. Time to perform the test was the main outcome. Kinematics (Optotrak, 100Hz) and clinical impairment/activity levels were evaluated. Spatiotemporal coordination was assessed with slope (IJC) and cross-correlation (LAG) between elbow and shoulder movements. Results: Compared to controls, individuals with stroke (Fugl-Meyer Assessment, FMA-UE: 51.9 +/- 13.2; Box & Blocks, BBT: 72.1 +/- 26.9%) made more curved endpoint trajectories using less shoulder horizontal-abduction. For construct validity, shoulder range (beta = 0.127), LAG (beta = 0.855) and IJC (beta = -0.191) explained 82% of FNT-time variance for ReachIn and LAG (beta = 0.971) explained 94% for ReachOut in patients with stroke. In contrast, only LAG explained 62% (beta = 0.790) and 79% (beta = 0.889) of variance for ReachIn and ReachOut respectively in controls. For convergent validity, FNT-time correlated with FMA-UE (r = -0.67, p < 0.01), FMA-Arm (r = -0.60, p = 0.005), biceps spasticity (r = 0.39, p < 0.05) and BBT (r = -0.56, p < 0.01). A cut-off time of 10.6 s discriminated between mild and moderate-to-severe impairment (discriminant validity). Each additional second represented 42% odds increase of greater impairment. Conclusions: For this version of the FNT, the time to perform the test showed construct, convergent and discriminant validity to measure UL coordination in stroke.