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

Abstract

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 α = 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.