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Parkinson’s Disease
Volume 2015, Article ID 970534, 8 pages
Research Article

Minimal Clinically Important Difference on Parkinson’s Disease Sleep Scale 2nd Version

1Doctoral School of Clinical Neuroscience, University of Pécs, Rét Utca 2, Pécs 7623, Hungary
2Department of Neurology, University of Pécs, Rét Utca 2, Pécs 7623, Hungary
3MTA-PTE Clinical Neuroscience MR Research Group, Rét Utca 2, Pécs 7623, Hungary

Received 28 June 2015; Accepted 10 September 2015

Academic Editor: Birgit Högl

Copyright © 2015 Krisztina Horváth et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background and Aims. The aim of the present study was to determine the estimates of minimal clinically important difference for Parkinson’s Disease Sleep Scale 2nd version (PDSS-2) total score and dimensions. Methods. The subject population consisted of 413 PD patients. At baseline, MDS-UPDRS, Hoehn-Yahr Scale, Mattis Dementia Rating Scale, and PDSS-2 were assessed. Nine months later the PDSS-2 was reevaluated with the Patient-Reported Global Impression Improvement Scale. Both anchor-based techniques (within patients’ score change method and sensitivity- and specificity-based method by receiver operating characteristic analysis) and distribution-based approaches (effect size calculations) were utilized to determine the magnitude of minimal clinically important difference. Results. According to our results, any improvements larger than −3.44 points or worsening larger than 2.07 points can represent clinically important changes for the patients. These thresholds have the effect size of 0.21 and −0.21, respectively. Conclusions. Minimal clinically important differences are the smallest change of scores that are subjectively meaningful to patients. Studies using the PDSS-2 as outcome measure should utilize the threshold of −3.44 points for detecting improvement or the threshold of 2.07 points for observing worsening.