Development of Health-related Quality of Life Instrument for Patients With Cystinosis

First, a literature review was conducted to identify relevant quality of life topics for the focus interviews. The development of the cystinosis-specific PROM will include three phases with patient recruitment: (1) focus interviews, (2) pilot-test and cognitive debriefing, and (3) field and re-test. 1. Focus interviews with up to 25 parents (of young patients aged 0 to 26) and 15 young patients (ages 8-26) per country (Germany, France, Spain and USA) will discuss aspects relevant to the young patient's quality of life. A pilot instrument version will be developed based on the interviews and then translated into the other project languages according to ISPOR guidelines. 2. The pilot instrument (translated) will be administered to patients and parents along with a cognitive debriefing to assess the comprehensibility, interpretation, and cultural relevance of the items. Up to 200 parents (25-50 per country) and 120 young patients (15-30 per country) will complete the pilot instrument and cognitive debriefing. 3. At least 300 parents (75 per country) and 180 young patients (45 per country) will complete the refined questionnaire as part of a field and re-test. The questionnaire will be filled out again after two weeks by at least 20% of the patients and parents to assess the test-retest reliability. The final product will be a psychometrically validated, easy to use, and conceptually appropriate quality of life instrument available in German, English, Spanish, and French for use in research and patient care.