Health related quality of life in Parkinson's disease: a systematic review of disease specific instruments

Objective: To compare and contrast disease-specific quality of life instruments in Parkinson's disease and assess their clinimetric properties. Methods: Two reviewers independently evaluated both thoroughness and results of studies regarding clinimetric characteristics of identified scales. Results: Twenty studies were found reporting on the clinimetric properties of four scales. The content validity of the Parkinson's disease questionnaire-39 item version (PDQ-39), the Parkinson's disease quality of life questionnaire (PDQL), and the “Fragebogen Parkinson LebensQualität” (Parkinson Quality of Life questionnaire; PLQ) was adequate to good, but for the Parkinson's impact scale (PIMS) it was insufficient. Construct validity of both the PDQ-39 and the PDQL was good, but for the PLQ and the PIMS this was insufficiently evaluated. Internal consistency of all scale totals and of subscale totals of the PDQL were good, whereas for the social support subscale of the PDQ-39 and four subscales of the PLQ this was inadequate. Test-retest reliability was not evaluated for the PDQL and was adequate in the other scales. Responsiveness was partially established for the PDQ-39, and not assessed for the other scales. The number of available translations, as well as the number of studies in which these instruments were used, differed considerably. Conclusions: The selection of an instrument partially depends on the goal of the study. In many situations however, the PDQ-39 will probably be the most appropriate HRQoL instrument. The PDQL may be considered as an alternative, whereas the PLQ may be considered in studies involving German speaking patients with Parkinson's disease. Use of the PIMS should be considered only as a means of identifying areas of potential problems.