Skip Navigation



Age and Ageing Advance Access published online on June 13, 2006
Age and Ageing, doi:10.1093/ageing/afl055
This Article
Right arrow FREE Full Text (PDF) Freely available
Right arrow supplementary data
Right arrow All Versions of this Article:
35/5/497    most recent
afl055v1
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Jenkinson, C.
Right arrow Articles by Fitzpatrick, R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Jenkinson, C.
Right arrow Articles by Fitzpatrick, R.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2006. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Received June 3, 2005
Accepted April 25, 2006

Article

The Parkinson’s Disease Questionnaire (PDQ-39): evidence for a method of imputing missing data

Crispin Jenkinson 1 *, Catherine Heffernan 2, Helen Doll 2, and Ray Fitzpatrick 3

1 University of Oxford, Department of Public Health, Old Road Campus, Headington, Oxford OX3 7LF, UK; Harris Manchester College, Oxford OX1 3TD, UK
2 University of Oxford, Department of Public Health, Old Road Campus, Headington, Oxford OX3 7LF, UK
3 University of Oxford, Department of Public Health, Old Road Campus, Headington, Oxford OX3 7LF, UK; Nuffield College, Oxford OX1 1NF, UK

* To whom correspondence should be addressed.
Crispin Jenkinson, E-mail: crispin.jenkinson{at}dphpc.ox.ac.uk


  Abstract

Background: the Parkinson’s Disease Questionnaire (PDQ-39) is the most widely used Parkinson’s specific measure of health status. It is increasingly used in treatment trials, sometimes as a primary end-point, where any missing data can potentially cause difficulties in analyses.

Objectives: the purpose of this article is to evaluate the Expectation Maximisation (EM) algorithm for the imputation of missing dimension scores on the 39-item PDQ-39.

Methods: a postal survey of patients diagnosed with Parkinson’s disease (PD). A total of 1,372 patients were surveyed and 839 (61.15%) questionnaires returned completed or partially completed. Of these, complete PDQ data were available in 715 (85.22%) cases. Data were deleted from this complete dataset and a sub-set of 200 respondents from this dataset and then imputed using the EM algorithm; results were then compared to the dataset before data deletion.

Results: results gained from imputation of data closely mirrored that of the complete dataset in each case. Descriptive statistics, mean scores and spread of scores were almost identical between original and imputed datasets. Furthermore, original and imputed datasets were highly correlated [intra-class correlation coefficient (ICC) = 0.93 or greater], and mean differences were small (±1.00).

Conclusions: the results suggest that the use of EM for the PDQ-39 provides data that closely mirrors the original when this has been deliberately removed. Consequently, EM is likely to be appropriate for trials using the PDQ that contains missing data points.

Keywords: Parkinson’s Disease Questionnaire, health status measurement, missing data, data imputation, elderly, PDQ-39.
Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 J Bone Joint Surg BrHome page
D. W. Murray, R. Fitzpatrick, K. Rogers, H. Pandit, D. J. Beard, A. J. Carr, and J. Dawson
The use of the Oxford hip and knee scores
J Bone Joint Surg Br, August 1, 2007; 89-B(8): 1010 - 1014.
[Abstract] [Full Text] [PDF]


Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.