Construct validity of the 9-hole peg test and purdue pegboard test in people with mild to moderately severe Parkinson's disease

Objectives To evaluate the construct validity of two dexterity measures, the 9-Hole Peg Test (9HPT) and Purdue Pegboard Test (PPT) in people with Parkinson’s disease (PD). Design Cross-sectional observational study. Setting Testing was conducted at the university or in participants’ homes. Participants Thirty community dwelling people with mild to moderately severe PD and no major upper limb comorbidities or cognitive impairments. Interventions Pegboard tests were administered in the ‘on’ and ‘end-of-dose’ phases of participants’ PD medication cycles. Participants rated hand function with two self-report questionnaires – the Manual Ability Measure-36 (MAM-36) and a subset of upper limb items from the MDS-UPDRS. To explore construct validity, we compared ‘on’ phase pegboard scores with normative values for unimpaired men and women and investigated relationships between pegboard scores and hand function questionnaires. Results In the ‘on’ phase, pegboard scores were poorer than normative values. Differences in individual subtest scores ranged between 10 and 41%. Correlations between self-reported hand function and pegboard scores were weak to moderately strong in the ‘on’ phase (r = 0.21–0.51), and weak at ‘end-of-dose’ (r = 0.13–0.22). Higher correlation coefficients were observed between hand function and PPT subtest scores than with hand function and 9HPT scores. Most participants reported difficulty with daily hand tasks. Conclusions We found evidence for construct validity supporting the use of the 9HPT and PPT to evaluate people with mild to moderately severe PD when ‘on’, but not at the ‘end-of-dose’. Results also suggest that the PPT may be more sensitive to PD-related changes in dexterity than the 9HPT