OBJECTIVES:

Currently available patient-reported outcome measures may not adequately capture the impact of OFF-Episodes (OEs) on health-related quality of life (HRQL) and daily functioning in Parkinson’s disease (PD). Thus, the applicant team recently developed a new 18-item instrument Off-Episode Quality Life Impact Scale (OFFELIA). This study aimed to examine the convergent and discriminative validity of OFFELIA with other measures of HRQL used in PD.

METHODS:

Participants completed the cross-sectional health and disease questionnaire “Impact and Communication on OFF Periods” as part of a standard schedule of activities at Fox Insight, an online data platform for people with PD developed by the MJ Fox Foundation as well as the EQ-5D-5L, The Penn Parkinson's Daily Activities Questionnaire-15 (PDAQ-15), Geriatric Depression Scale (GDS), Unified Parkinson's Disease Rating Scale (UPDRS), Non-Motor Symptoms Questionnaire (NMSQ). Convergent validity was examined between the summary score of two OFFELIA subscales and EQ-5D-5L, PDQ-8, PDAQ-15, GDS, UPDRS-II, NMSQ scores using Pearson correlations (r). Discriminative validity was examined using known group comparisons (KGC) using Cohen’s effect sizes (ES) and analysis of variance F-ratios based on unpredictability, duration, onset and frequency of OEs.

RESULTS:

569 individuals with PD completed the questionnaire. Moderate associations (0.3 ≥ r > 0.7) were found between the OFFELIA subscales and the EQ-5D-5L index score, EQ VAS, PDQ-8, UPDRS-II, GDS and NMSQ. OFFELIA can discriminate patients better than the EQ-5D-5L and PDQ-8 across different severity levels of unpredictability (F-ratio: 2.44 and 2.55 respectively), duration (F-ratio: 3.3 and 2.49 respectively), onset (F-ratio: 6.1 and 2.34 respectively) and frequency (F-ratio: 3.18 and 2.04 respectively).

CONCLUSIONS:

Initial evidence supports the construct validity of OFFELIA, a new instrument for evaluating the impact of OEs on HRQL and functioning in PD patients, and demonstrates its potential to better capture the impact of OEs and clinical benefits of new and existing therapeutic strategies.