Investigation of the psychometric properties of the squares test in measuring hand function in Parkinson's disease

The aim of the study was to determine reliability and validity of the Squares Test (ST) in Parkinson's disease (PD). Fifty-seven patients with Idiopathic PD and 50 healthy people were included in the study. At baseline, the ST, Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn and Yahr (H&Y) Scale, Berg Balance Scale (BBS) and Trunk Impairment Scale (TIS) was applied to the PS group when the patients were "on" period. The ST was repeated after seven days from the first application when PD group were "on" period to evaluate its reliability. Test-retest reliability of the ST was excellent in the PD group for both hands (ICC2,1=0.955, ICC2,1=0.935, respectively). Discriminatory power of the ST between groups was excellent. The ROC area under the curve was 0.936 (AUC=0.936). Discriminative optimal cut-off point between groups was determined as 114 dots (sensitivity 94%, specificity 84%). The ST was well correlated with UPDRS total and UPDRS motor examination score and moderately correlated with H&Y Scale (r=-0.690, r=-0.637, r=-0.598, p<0.001, respectively). The ST was strongly correlated with BBS and TIS score (r=0.812, r=0.843, p<0.001, respectively). The ST is a valid and reliable measurement for measuring hand functions and used to assess hand functions in PD. Also, the relationship between hand functions and balance, trunk control, stage of disease and disability level in PD indicates importance of hand functions in assessment and treatment of PD. Parkinson's disease, Hand function, Squares test, Reliability and Validity