Objective: The aim of this study was to develop and validate a patient-reported outcome measure to evaluate body image concerns in head and neck cancer (HNC) patients.
Methods: Items were created using a combination of deductive (eg, US Food and Drug Administration Qualification of Clinical Outcome Assessments, literature review) and inductive approaches (eg, subject matter experts, HNC patients). Items were translated for use in both Canadian English and Canadian French using back-translation. A two-step empirical validation process using the Classical Test Theory (CTT) and Rasch Measurement Theory (RMT) was conducted with 224 and 258 HNC patients, respectively, having undergone disfiguring surgery within the past 3 years.
Results: Analyses suggest two subscales for MBIS-HNC: social discomfort (10 items) and negative self-image (11 items). The McGill Body Image Concerns Scale-Head and Neck Cancer (MBIS-HNC) is reliable with high internal consistency (0.98), high test-retest reliability over a two-week period (ICC = 0.88), moderate to high convergent validity (range r = 0.43-0.81), and divergent validity (range r = 0.12-0.15). RMT was used in addition to CTT. Disordered thresholds led to the modification of the number of response options, and items were deleted based on differential item functioning and high local dependency. Unidimensionality of both subscales and supporting a total score was confirmed. The measure was however characterized by the presence of an important floor effect, confirmed with poor targeting as demonstrated by the person-item threshold distribution.
Conclusion: Evidence gathered from our theory-driven validation study using CTT and RMT provides practitioners and researchers with a useful and easy to use self-report measure.
Keywords: Classical Test Theory; McGill Body Image Concerns Scale (MBIS); Rasch Measurement Theory; body image; disfigurement; functional impairment; head and neck cancer; quality of life.
© 2018 John Wiley & Sons, Ltd.