Evidence map›Paper›PMID 17442762›Full record

ArticleJournal of neurology, neurosurgery, and psychiatry2007

The 39 item Parkinson's disease questionnaire (PDQ-39) revisited: implications for evidence based medicine.

Peter Hagell, Carita Nygren

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In one paragraph

Article in Journal of neurology, neurosurgery, and psychiatry, 2007. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 83 papers, 9 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
83citing papers in PubMed, 9 pooled it
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

83 citing papers in PubMed, 9 syntheses or guidelines pooled it.

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  3. Clinical and genetic characteristics ofJournal of medical genetics · 2025
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23 more citing papers are in PubMed but not listed here.

4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

2 authors.

Peter HagellDepartment of Health Sciences, Lund University, PO Box 157, SE-221 00 Lund, Sweden. Peter.Hagell@med.lu.se
Carita Nygren

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundThe 39 item Parkinson's disease questionnaire (PDQ-39) is the most widely used patient reported rating scale in Parkinson's disease. However, several fundamental measurement assumptions necessary for confident use and interpretation of the eight PDQ-39 scales have not been fully addressed.

methodsPostal survey PDQ-39 data from 202 people with Parkinson's disease (54% men; mean age 70 years) were analysed regarding psychometric properties using traditional and Rasch measurement methods.

resultsData quality was good (mean missing item responses, 2%) and there was general support for the legitimacy of summing items within scales without weighting or standardisation. Score reliabilities were adequate (Cronbach's alpha 0.72-0.95; test-retest 0.76-0.93). The validity of the current grouping of items into scales was not supported by scaling success rates (mean 56.2%), or factor and Rasch analyses. All scales represented more health problems than that experienced by the sample (mean floor effect 15%) and showed compromised score precision towards the less severe end.

conclusionsOur results provide general support for the acceptability and reliability of the PDQ-39. However, they also demonstrate limitations that have implications for the use of the PDQ-39 in clinical research. The grouping of items into scales appears overly complex and the meaning of scale scores is unclear, which hampers their interpretation. Suboptimal targeting limits measurement precision and, therefore, probably also responsiveness. These observations have implications for the role of the PDQ-39 in clinical trials and evidence based medicine. PDQ-39 derived endpoints should be interpreted and selected cautiously, particularly regarding small but clinically important effects among people with less severe problems.

Indexed as

Disability EvaluationEvidence-Based MedicineMobility LimitationSick RoleSurveys and QuestionnairesActivities of Daily LivingAdultAgedAged, 80 and overAntiparkinson AgentsCognition DisordersFemaleGeriatric AssessmentHumansLevodopaMaleAntiparkinson AgentsLevodopa

Identifiers

PMID17442762
PMCPMC2117601

What OpenQuestion holds

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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.