Patient-reported health status questionnaires intend to assess illness and therapy from the patients' perspective. To provide fair and valid assessments, they should be equally relevant to major subsets of respondents. Furthermore, disease-specific measures are assumed to be perceived as more relevant than generic ones. This study assessed these assumptions among people with Parkinson's disease.
Cross-sectional data from 202 people with Parkinson's disease (54% men; mean age, 70) were analyzed regarding patient-rated relevance and predictors of patient-rated poor relevance of two generic [the 36-item Short Form Health Survey (SF-36) and Nottingham Health Profile (NHP)] and one disease-specific [Parkinson's Disease Questionnaire (PDQ-39)] health status questionnaire.
There were no differences in relevance ratings across the questionnaires. Poorer overall quality of life [odds ratio (OR), 2.459] and mental health (OR, 1.023) were associated with poorer patient-rated relevance of the SF-36, and higher age was associated with poorer patient-rated relevance of the PDQ-39 (OR, 1.040). No significant predictors were found for the NHP.
The PDQ-39 failed to meet the assumption that disease-specific scales are more relevant than generic ones. Nevertheless, the most important implication of this study is an ethical one. Because the relevance of the SF-36 and PDQ-39 is perceived as poorer by those who fare least well and by older people, these scales may not reflect the perspectives of these groups. This challenges bioethical principles and threatens scientific validity. Perceived relevance of patient-centered outcomes needs to be considered, or the voice of vulnerable groups may be silenced, fair inferences prohibited, and opportunities for improved care lost.