Quality of Life Research

, Volume 22, Issue 5, pp 1065–1072 | Cite as

Mapping of the PDQ-39 to EQ-5D scores in patients with Parkinson’s disease

  • Megan K. Young
  • Shu-Kay Ng
  • George Mellick
  • Paul A. Scuffham



The EuroQoL (EQ-5D) is ideal to compare quality of life across conditions. However, the Parkinson’s Disease Questionnaire (PDQ-39) is often the only quality-of-life instrument used in Parkinson’s disease research. We aimed to identify associations between PDQ-39 domains and EQ-5D domains, and compare different methods of developing a function to map the PDQ-39 to EQ-5D scores.


Adults with Parkinson’s disease self-completed both instruments. Ordinal regression identified associations between PDQ-39 domain scores and each EQ-5D domain. Modeling (n = 80) and validation sets (n = 16) were randomly generated. Overall performance of four methods of mapping the PDQ-39 to EQ-5D scores (using PDQ-39 domains and total score in ordinal and linear regression) was assessed with the validation set, followed by assessing the equivalence of observed and predicted EQ-5D scores on the full dataset controlling for sociodemographic factors.


Different sets of PDQ-39 domains were associated with each EQ-5D domain. For example, PDQ-39 “Activities of Daily Living” and “Social Support” were associated with EQ-5D “Personal Care,” while PDQ-39 “Emotional Well-being” was associated with EQ-5D “Anxiety/Depression.” Over one-third (37.5 %) of predictions from ordinal regressions had an error <0.01 % (compared to 6.3 % for linear regressions). The EQ-5D scores predicted with ordinal regression using PDQ-39 domains were similar in distribution and association with sociodemographic factors to the observed EQ-5D scores.


Of the four methods tested, using PDQ-39 domains in ordinal regression was superior for mapping EQ-5D scores. The function reported here may prove particularly useful for cost-utility analyses comparing Parkinson’s disease with other conditions.


Quality of life PDQ-39 EQ-5D Parkinson’s disease Economic evaluation 



Censored least absolute deviations


Deep brain stimulation




EuroQoL utility index


Interquartile range


Mean absolute deviation


Missing at random


Missing completely at random


Ordinary least squares


Parkinson’s Disease Questionnaire


Queensland Parkinson’s disease Project


Root mean squared error


Statistical Package for the Social Sciences


United Kingdom


Visual analogue scale


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Megan K. Young
    • 1
  • Shu-Kay Ng
    • 2
  • George Mellick
    • 3
  • Paul A. Scuffham
    • 2
  1. 1.School of Medicine, Population and Social Health Research Group, GHIGriffith UniversityMeadowbrookAustralia
  2. 2.School of Medicine, Griffith Health InstituteGriffith UniversityMeadowbrookAustralia
  3. 3.Eskitis Institute for Cell and Molecular TherapiesGriffith UniversityNathanAustralia

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