Validity and reliability of the Chinese (Singapore) version of the Parkinson's Disease Questionnaire (PDQ-39)

Abstract

Objective: The purpose of the study was to validate the Chinese (Singapore) version of the Parkinson's Disease Questionnaire (PDQ-39CSV) and its briefer version (PDQ-8CSV). Methods: A convenience sample of Chinese-speaking Singaporeans with Parkinson's disease (PD) (n = 63) completed a questionnaire containing the PDQ-39CSV and the Chinese (Singapore) EQ-5D. A subgroup also participated in a retest and/or a focus group discussion. A priori hypotheses were tested by examining correlations between PDQ-39CSV, PDQ-8CSV and EQ-5D scores and using principal component factor analysis. Reliability was assessed using Cronbach's α and intra-class correlation coefficients (ICC). Results: Thirty-two PDQ-39CSV items correlated satisfactorily with their hypothesized dimensions (Spearman's ρ ≥ 0.4). Factor analysis yielded a component on which all 8 PDQ-39CSV dimensions were substantially loaded (loading range: 0.53-0.89). As hypothesized, the PDQ-39CSV and PDQ-8CSV summary indices were highly correlated (Pearson's r:0.95, ICC:0.94); correlations between related PDQ and EQ-5D scores were generally strong (Spearman's ρ: 0.38-0.76, p < 0.001 for all). Cronbach's α values ranged from 0.64 to 0.90 and ICC values from 0.66 to 0.86. Conclusion: This study provides preliminary evidence supporting validity and reliability of both the PDQ-39CSV and its briefer version.