Instrument Information
- A 33-item Parkinson’s Disease (PD) specific health-related quality of life (HRQoL) measure.
- Developed in the US [Welsh et al, 2002] for use in individuals diagnosed with idiopathic PD.
- PD-specific motor symptoms not directly assessed as the instrument is intended to be a complement to the UPDRS which provides a comprehensive assessment of motor symptomatology.
- Initial psychometric testing of the instrument was conducted in a convenience sample of outpatient clinic attendees with physician-confirmed idiopathic PD. The subjects were selected from 13 outpatient movement disorder clinics in the US and Canada.
- Factor analysis with varimax rotation supported a seven-factor solution. Three of the original four domains used as the conceptual framework during the qualitative data collection and four additional domains emerged.
- Mean age of the total sample was 65.4, 62% were male, 98% were Caucasian, and the average educational level was 14.7 years. 82% of the subjects were in mid-stage disease.
- Subjects self-administered an instrument packet containing demographics questions, the PDQUALIF, SF-36 and Sickness Impact. Associations between the PDQUALIF total and subscale scores and those of the SF-36 and SIP were all highly significant with associations tending to be stronger with the SIP than with the SF-36.
- Final version of the PDQUALIF© consists of seven domains: social/role function (nine items), self-image/sexuality (seven items), sleep (three items), outlook (four items), physical function (five items), independence (two items), urinary function (two items), and global HRQoL (one item).
- The scale showed good internal reliability with Cronbach's α=0.89 and the range for the seven subscales was 0.55 to 0.85. Four of seven subscales, however, had Cronbach’s α estimates of less than 0.70 (0.55-0.62) which may have resulted from the small number of items in those subscales.
- Overall test-retest reliability was good (r=0.88). Test-retest reliability was shown to be good for all subscales.
- Support for item convergence and discrimination was provided by the multitrait scaling analysis.
- All subscales demonstrated reasonable score variability with the exception of the Independence subscale which had a noticeable floor effect (78.9%) and the Sleep subscale which demonstrated minor floor effects (8.7%).
- Completion time for the scale is 10 to 15 minutes.
