title: Validity and reliability of the PDQ-39 and the PDQ-8 in English-speaking Parkinson's disease patients in Singapore.
abstract: The purpose of the study was to assess the validity and reliability of the Parkinson's disease questionnaire (PDQ-39, UK English version) as well as its briefer version (the PDQ-8) among Asian patients with Parkinson's disease (PD) in Singapore. Eighty-eight patients recruited from movement disorder clinics or patient support groups completed the PDQ-39 and EQ-5D, a generic health related quality of life questionnaire previously validated for use in Singapore. PDQ-39 items showed good convergent and discriminant validity. Construct validation against the EQ-5D showed strong correlation between these scales as hypothesised (Spearman's rho: 0.53-0.71, P<0.001 for all). Factor analysis yielded a component on which all eight PDQ-39 dimensions were substantially loaded (loading range: 0.50-0.79). The PDQ-39 also demonstrated acceptable internal consistency (Cronbach's alpha: 0.59-0.94) and test-retest reliability (intra-class correlation coefficient:0.67-0.87, n=68). Six of eight PDQ-8 items showed the strongest correlation with their PDQ-39 dimensions as hypothesised. PDQ-39 and PDQ-8 summary indexes were highly correlated (Pearson's r=0.96, ICC=0.95), and both were strongly correlated with the EQ-5D utility index and EQ-5D visual analogue scale (P<0.001). We conclude that the PDQ-39 and PDQ-8 are valid and reliable disease-specific HRQoL instruments for PD in Singapore.
authors.affiliation: Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433. louis_tan@nmi.com.sg
authors.forename: Louis C S
authors.initials: LC
authors.lastname: Tan
authors.forename: Nan
authors.initials: N
authors.lastname: Luo
authors.forename: Mohammed
authors.initials: M
authors.lastname: Nazri
authors.forename: Shu Chuen
authors.initials: SC
authors.lastname: Li
authors.forename: Julian
authors.initials: J
authors.lastname: Thumboo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001007:Anxiety / Q000150:complications / Q000523:psychology; D003071:Cognition; D003142:Communication; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000523:psychology; D015203:Reproducibility of Results; D012846:Singapore; D012944:Social Support; D011795:Surveys and Questionnaires