Development and preliminary evaluation of the Neurofibromatosis Type 1 Adult Quality of Life (NF1-AdQoL) questionnaire

Background Neurofibromatosis Type 1 (NF1) is a variable and unpredictable multisystem genetic disorder that predisposes to medical complications, cognitive impairment and disfigurement, of all which can impact negatively upon the health-related quality of life (HRQoL) of affected adults. Aims To develop and validate a disease-specific HRQoL adult questionnaire to evaluate effects of NF1 from the patient's viewpoint. Methods The Neurofibromatosis Type 1 Adult Health-related Quality of Life questionnaire (NF1-AdQoL) was based on patient interviews (n = 8), clinician survey and questionnaire pilot study. Adults with NF1 (n = 114, aged 18-40 years) were recruited from three Australian genetics clinics and completed the NF1-AdQoL, the 29-item Skindex (Skindex-29) and the 36-item Short Form, version 2 (SF-36v2) questionnaires. An exploratory factor analysis of the NF1-AdQoL was conducted to assess construct validity. Convergent and discriminant validity of the NF1-AdQoL was determined by using multitrait multimethod analysis with Skindex-29 and SF-36v2 scores. Results Factor analysis indicated that 62.7% of the common variance between the questionnaires could be explained by three factors: 'emotions associated with cosmetic appearance' (12 items), 'functioning - social and learning' (11 items) and 'physical symptoms' (8 items). NF1-AdQoL had good internal consistency (Cronbach alpha = 0.96). Convergent validity was confirmed by moderate associations with similarly named scales of the Skindex-29 and SF-36v2. Results from all three HRQoL questionnaires indicated overall healthy HRQoL for young to early middle-aged adults with NF1. Conclusion The NF1-AdQoL is a relatively valid, feasible and fairly easy to read tool to measure the HRQoL of adults with NF1. Further evaluation is required to determine the test-retest reliability, responsiveness and validity of the NF1-AdQoL in larger adult NF1 cohorts.