Multiple patient reported outcomes have been used in order to measure quality of life in Cystic Fibrosis in Spain, but it is important to find a consensus on which is the most reliable and valid quality of life instrument.
OBJECTIVE: To compare three quality of life questionnaires widely used among CF patients in order to prove which of them is more valid and reliable when measuring quality of life and disease severity.
METHODS: Two disease-specific questionnaires: Cystic Fibrosis Questionnaire-Revised (CFQ-R), and St. George Respiratory Questionnaire (SGRQ), and a generic instrument: the Short-form-36 health survey (SF-36), were simultaneously administered in to 75 adolescents and adults with CF (≥14 years old), 20 of which were awaiting lung transplantation. Internal consistency (Cronbach alpha), and convergent and construct validity were calculated, as well as external validity (correlations of each questionnaire with demographic and clinical variables: lung transplantation list, FEV1, pulmonary exacerbation and intravenous treatment, digestive disorders, etc.).
RESULTS: Similar reliability, but different validity of the questionnaires was shown. Strong correlations (≥0.70) were found between several of the scales in the three questionnaires: physical functioning, role limitation, energy and vitality, and mental health. The CFQ-R allows a better differentiation of the varying levels of disease severity, plus it has disease-specific scales.
DISCUSSION: An instrumentsā€˜ validity and applicability should be considered when choosing a questionnaire to measure HRQoL in CF patients. The CFQ-R proved to be the most suitable, although some of its subscales could be reviewed.