A review of health-related quality-of-life concepts and measures for Parkinson's disease

Parkinson's disease affects individuals' health-related quality of life (HQL). Including standardized HQL assessments in therapeutic clinical trials will broaden our understanding of treatment efficacy. Selecting appropriate HQL measures for clinical studies requires consideration of their comprehensiveness, psychometric properties and feasibility. To facilitate selection, this manuscript reviews the HQL areas affected by Parkinson's disease and available Parkinson's disease-specific HQL measures: the Parkinson's Disease Questionnaire-39 (PDQ-39) and the Parkinson's Disease Quality-of-Life Questionnaire (PDQL). Based on a literature review and consultation with HQL experts, five clinicians and three patients, 12 areas of HQL were identified as particularly relevant to Parkinson's disease: physical function, mental health/emotional well being, self-image, social function, health-related distress, cognitive function, communication, sleep and rest, eating, role function, energy/fatigue, and sexual function. The PDQ-39 measures all areas except for self-image and sexual function. The PDQL measures all areas except for eating and role function. Both measures are brief and are designed and validated to be self-completed by patients. Both measures demonstrate adequate internal consistency (PDQ-39: 0.72-0.95; PDQL: 0.80-0.87) and evidence of cross-sectional validity with patient-reported measures of similar concepts. The PDQ-39 also demonstrates reproducibility (0.68-0.94), significant associations with clinical measures and preliminary evidence of responsiveness. Applications of the PDQ-39 and PDQL to clinical trials will contribute greatly towards their continued validation and interpretation.