Validation of an Estonian version of the Parkinson's Disease Questionnaire (PDQ-39).
BACKGROUND
Diagnosis and management of Parkinson's disease (PD) rely heavily on evaluation of clinical symptoms and patients' subjective perception of their condition. The purpose of this study was to evaluate the validity, acceptability, and reliability of the Estonian version of the 39-question Parkinson 's disease Questionnaire (PDQ-39).


METHODS
Study subjects were approached during their regular clinic follow-up visits. 104 patients consented to the study and 81 completed questionnaires were used for subsequent testing of psychometric characteristics, validity and reliability.


RESULTS
The content validity was assessed through qualitative content analysis during the pilot study. The patients indicated that the questions were relevant to measure the quality of life of people with PD. The analysis of means showed that the ceiling and floor effects of domain results were within the limits of 15% of Summary Index and of all domains except Stigma, Social Support and Communication where the ceiling effect was 16% to 24% of the responses. Convergent validity was interpreted through correlation between disease severity and PDQ-39 domains. There was a statistically significant difference between the domain scores in patients with mild versus moderate PD in domains of Mobility, ADL, and Communication but not for Stigma, Social Support and Cognition. The reliability was good, Cronbach alpha for all domains and summary index was over 0.8 and item-test correlations between domains and summary index ranged from 0.56 to 0.83.


CONCLUSIONS
The psychometric characteristics of an Estonian version of the PDQ-39 were satisfactory. The results of this study were comparable to the results of previous validation studies in other cultural settings in UK, USA, Canada, Spain and Italy. The Estonian version of the PDQ-39 is an acceptable, valid and reliable instrument for quality of life measurement in PD patients.
Krikmann
Ulle
U
Department of Neurology and Neurosurgery, University of Tartu, Tartu 51014, Estonia. ylle.krikmann@kliinikum.ee
Taba
Pille
P
Lai
Taavi
T
Asser
Toomas
T
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D004957:Estonia; D005260:Female; D017144:Focus Groups; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000145:classification / Q000523:psychology; D010342:Patient Acceptance of Health Care / Q000523:psychology* / Q000706:statistics & numerical data; D010865:Pilot Projects; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012944:Social Support; D011795:Surveys and Questionnaires; D014177:Translations