The Reliability and Validity of the Manual Ability Measure-36 in Patients with Parkinson’s Disease

Objective: Although impaired manual dexterity is one of the most disabling symptoms in patients with Parkinson’s disease (PD), there is no reliable and valid patient-reported outcome measure (PROM) for assessing dexterity. Therefore, this study aimed to investigate: (1) The test-retest reliability of the manual ability measure-36 (MAM-36) in patients with PD; (2) the minimum detectable change (MDC) in the MAM-36 scores; (3) the concurrent and known-groups validity of the MAM-36 scores; and (4) the cut-off score that best discriminates patients with PD from healthy individuals.
Materials and Methods: This was a cross-sectional study. The MAM-36 was repeated after 4 weeks to determine the test-retest reliability which was calculated with the intraclass correlation coefficient (ICC), Bland-Altman plots, and MDC. The concurrent validity was assessed using correlations between the MAM-36 and nine-hole peg test, Movement Disorders Society Unified Parkinson’s Disease Rating scale (MDS-UPDRS), MDS-UPDRS II, MDS-UPDRS III, Hoehn and Yahr stage, and 8-item PD questionnaire. The known-groups validity was determined by comparing the MAM-36 scores between patients with PD and healthy individuals. Receiver operating characteristic analysis was used to determine the cut-off score for the MAM-36 to best discriminate patients with PD from healthy individuals.
Results: Thirty six patients with PD and 32 healthy individuals were included. Excellent test-retest reliability was found (ICC: 0.953). The Bland-Altman plot demonstrated a high agreement. The MDC was 2.33. The MAM-36 had fair to high correlations with the other outcome measurements (correlation coefficients ranged from -0.473 to -0.763, p<0.05 for all). Patients with PD had lower scores than healthy individuals in terms of the MAM-36 (p<0.001). The cut-off score of 76.50 best distinguished patients with PD from healthy individuals.
Conclusion: The MAM-36 is a reliable and valid measurement for assessing manual dexterity in patients with PD. It is also the only clinically available PROM in assessing manual dexterity for patients with PD in the Turkish population.