Objective: This study is aimed at assessing and interpreting the changes in motor rating scales for Parkinson’s disease (PD) over a 2-year longitudinal study.

Background: PD is a progressively disabling disease, affecting both motor and non-motor aspects. Several statistical techniques allow for quantifying the change over time and offering threshold values to ascertain clinical importance.

Methods: This was an international, longitudinal study in a sample of 735 PD patients. Patients were assessed at baseline and at a two-year follow-up using Hoehn and Yahr staging (HY), the Scales for Outcomes in PD (SCOPA)-Motor and the Clinical Impression of Severity Index for PD (CISI-PD). Non-parametric tests, responsiveness statistics, and three proposed distribution-based thresholds (standard error of measurement, SEM; half a standard deviation, at baseline, ½ SDB; and 10% of maximum total score, MTS) and their average value (“estimated change value”, ECV) were calculated to estimate the magnitude and importance of the change.

Results: Patients, aged 65.5 (SD: 10.3), with disease duration of 6.5 (SD: 5.5) years, were predominantly male (64.7%). At baseline, 21.5% of the sample was HY stage 1, 43.9% HY2, 27.5% HY3, 5.8% HY4 and 1.2% HY5. There were significant differences in HY, SCOPA-Motor and CISI-PD scores between baseline and follow-up (p<0.001), with worse scores at the end of the studyperiod. Relative change was 11.3% for SCOPA-Motor, with a range of 8.9%-17.56% for its subscales; and 12.7% for CISI-PD, with a range of 6.25%–25.0% for its domains. Effect sizes were 0.20 for SCOPA-Motor (subscales range: 0.13-0.21) and 0.21 for CISI-PD (domains range: 0.13-0.20). The change ranged from 0.98 (SEM) to 7.50 (10% of MTS) for SCOPA-Motor, and from 0.76 (SEM) to 2.4 (10% of MTS) for CISI-PD. The ECV threshold was 4.51 for SCOPA-Motor and 1.71 for CISI-PD. Therefore, the observed differences between baseline and follow-up (2.0 for SCOPA-Motor, 0.84 for CISI-PD) did not reach the respective ECVs.

Conclusions: Motor symptoms showed a clear trend towards worsening, inspite of treatment, in the 2-year period, although the change was of little magnitude. Considering the threshold values, the change was not clinically relevant,as a whole. Additional research to settle the suitability of these thresholds for rater-based scales is needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/changes-in-motor-symptoms-of-parkinsons-disease-2-year-follow-up-of-735-cases/