Article Text
Abstract
Objectives The aim of this study was to adapt the Systemic Sclerosis Quality of Life Questionnaire (SScQoL) into six European cultures and validate it as a common measure of quality of life in systemic sclerosis (SSc).
Methods This was a seven-country (Germany, France, Italy, Poland, Spain, Sweden and UK) cross-sectional study. A forward–backward translation process was used to adapt the English SScQoL into target languages. SScQoL was completed by patients with SSc, then data were validated against the Rasch model. To correct local response dependency, items were grouped into the following subscales: function, emotion, sleep, social and pain and reanalysed for fit to the model, unidimensionality and cross-cultural equivalence.
Results The adaptation of the SScQoL was seamless in all countries except Germany. Cross-cultural validation included 1080 patients with a mean age 58.0 years (SD 13.9) and 87% were women. Local dependency was evident in individual country data. Grouping items into testlets corrected the local dependency in most country specific data. Fit to the model, reliability and unidimensionality was achieved in six-country data after cross-cultural adjustment for Italy in the social subscale. The SScQoL was then calibrated into an interval level scale.
Conclusion The individual SScQoL items have translated well into five languages and overall, the scale maintained its construct validity, working well as a five-subscale questionnaire. Measures of quality of life in SSc can be directly compared across five countries (France, Poland Spain, Sweden and UK). Data from Italy are also comparable with the other five countries although require an adjustment.
- systemic sclerosis
- quality of life
- outcomes research
- patient perspective
- health services research
This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Statistics from Altmetric.com
Footnotes
Handling editor Josef S Smolen
Contributors AR (professor of clinical biomechanics) is the principal investigator, designed the study, led the grant application, oversaw the project and undertook the statistical analyses, interpretation of the results and revised the study report for intellectual content. MN (senior lecturer in rheumatology nursing) codesigned the study with AR and BA-P, drafted the statistical analysis plan, contributed to the grant application, coordinated the project, undertook the statistical analyses, interpretation of the results and drafted the study report and revised it for intellectual content. BA-P (clinical post doctoral research fellow) was a member of the study team, a co-applicant on the study grant, contributed to the drafting of the manuscripts and revised it for intellectual content. YA (professor of rheumatology, rheumatologist) led the study team in France, contributed to the drafting of the study report and revised it for intellectual content. FDG (associate professor, head of scleroderma programme, rheumatologist) was a member of the study team, a co-applicant on the study grant, contributed to the drafting of the manuscripts and revised it for intellectual content. MF (resident physician and biostatistician) was a member of the study team in Germany, contributed to the translation of the SScQoL, data collection and drafting and revising the manuscripts for intellectual content. SG-D (rheumatology nurse specialist) led the study team in Spain, contributed to the drafting of the manuscripts and revised it for intellectual content. RH (associate professor of rheumatologist) was a member of the study team in Sweden, contributed to the drafting of the manuscripts and revised it for intellectual content. CK (physician assistant) was a member of the study team in Germany, contributed to the drafting of the manuscripts and revised it for intellectual content. MM-C (professor of rheumatology and medicine) led the study team in Italy, contributed to the drafting of the manuscripts and revised it for intellectual content. UM-L (professor of rheumatology) led the study team in Germany, contributed to the drafting of the study report and revised it for intellectual content. GS (associate professor, rheumatology occupational therapist) led the study team in Sweden, contributed to the drafting of the manuscripts and revised it for intellectual content. VT-S (consultant rheumatologist) was a member of the study team in Spain, contributed to the drafting of the manuscripts and revised it for intellectual content. TS (consultant rheumatologist) was a member of the study team in Germany, responsible for data collection in Germany. He contributed to the drafting of the manuscripts and revised it for intellectual content. MS (senior lecturer in nursing) led the study team, adaptation of the SScQoL and data collection in Poland and contributed to the drafting of the study report and revised it for intellectual content. JS (english instructor) was a member of the study team in Poland, responsible for the translation process of the SScQoL, contributed to the drafting of the study report and revised it for intellectual content. SS (professor of rheumatology) was a member of the study team in Poland, responsible for data collection for the validation of the SScQoL, contributed to the drafting of the study report and revised it for intellectual content. All authors read and approved the final version.
Funding MN and AR declare financial support (grant) for the submitted work from European League Against Rheumatism (grant reference HPR019).
Disclaimer The funder was not involved in the preparation of the study protocol, running of the study, and analysis or preparation of the report. There are no other relationships or activities that could appear to have influenced the submitted work.
Competing interests All authors have completed the unified competing interests form at http://www.icmje.org/coi_disclosure.pdf (available from the corresponding author) . The corresponding author had full access to all the study data and shares the final responsibility for publication with all coauthors.
Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.
Ethics approval This was a multicentre study conducted in seven countries (Germany, France, Italy, Poland, Spain, Sweden and UK) and was approved by local ethical committees or institutional review boards in each participating country.
Provenance and peer review Not commissioned; externally peer reviewed.