title: Health status measurement in Parkinson's disease: validity of the PDQ-39 and Nottingham Health Profile.
abstract: We assessed the feasibility and psychometric properties of two commonly used health status questionnaires in Parkinson's disease (PD): the generic Nottingham Health Profile (NHP) and the disease-specific 39-item Parkinson's disease Questionnaire (PDQ-39), from a cross-sectional postal survey of PD patients (N = 81), using traditional and Rasch measurement methodologies. Overall response rate was 88%. Both questionnaires were found feasible, although the NHP performed less well. The PDQ-39 had fewer floor effects and was better able to separate respondents into distinct groups than the NHP, whereas the latter exhibited less ambiguous dimensionality and better targeting of respondents with non-extreme scores. Reliability and validity indices were similar, and potential differential item functioning by age and gender groups was found for both questionnaires. PDQ-39 response alternatives indicated ambiguity. With few exceptions, questionnaire scales were unable to meet recommended standards fully. While preliminary, this study illustrates the need for thorough evaluation of outcome measures and has implications beyond the questionnaires used here. Although promising, both questionnaires warrant further developmental work and stronger support of measurement validity before they could be considered fully suitable for valid use in PD, in particular in earlier stages of the disease.
authors.affiliation: Section of Restorative Neurology, Department of Clinical Neuroscience, University Hospital, Lund, Sweden. peter.hagell@neurol.lu.se
authors.forename: Peter
authors.initials: P
authors.lastname: Hagell
authors.forename: Diane
authors.initials: D
authors.lastname: Whalley
authors.forename: Stephen P
authors.initials: SP
authors.lastname: McKenna
authors.forename: Olle
authors.initials: O
authors.lastname: Lindvall
mesh_terms: D000203:Activities of Daily Living / Q000145:classification / Q000523:psychology; D000368:Aged; D000369:Aged, 80 and over; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D005240:Feasibility Studies; D005260:Female; D015577:Geriatric Assessment / Q000706:statistics & numerical data; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D007802:Language; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D010300:Parkinson Disease / Q000453:epidemiology* / Q000523:psychology; D011594:Psychometrics / Q000706:statistics & numerical data; D011788:Quality of Life / Q000523:psychology; D015203:Reproducibility of Results; D018434:Sickness Impact Profile