Abstract
Introduction: The need to involve patients in developing and evaluating health care interventions is now well -recognized. This study assesses and refines the Orthodontic Treatment Impact Questionnaire for use as a patient-reported outcome in an interventional clinical trial to evaluate and compare any orthodontic interventions. Methods: The face and content validity of a previously developed questionnaire were tested in 2 focus groups involving adolescents aged 11-17 years. They were wearing a range of orthodontic appliances and at different treatment stages. A similar cross-sectional convenience sample completed the questionnaire during routine appliance adjustment appointments. A Rasch model, using item response theory, was used for item reduction, assessment of the response format, and differential item functioning. Spearman???s rank correlation was used to assess construct validity, Cronbach a for internal consistency and reliability, and intraclass correlation coefficient for test-retest reliability. Results: Seven adolescents (4 females, 3 males) were involved in the initial testing; 181 (117 females, 64 males; mean age, 14.7 6 1.5 years) completed the ques-tionnaire once and 41 twice. The initial measure demonstrated a misfit to the Rasch model. Ten of the original 31 items had disordered thresholds and were removed. The 5-point scale was changed to a 3-point scale. None of the participants demonstrated a misfit to the model. Construct validity (P = 0.480), internal consistency (Cronbach a = 0.827) and test-retest reliability (intraclass correlation coefficient = 0.85; 95% confidence interval, 0.73-0.92) were good. Conclusions: The initial Orthodontic Treatment Impact Questionnaire was tested and modified using item response theory. The modified questionnaire demonstrated good construct val-idity, reliability, and internal consistency. Further testing to assess generalizability and longitudinal responsive-ness is required. (Am J Orthod Dentofacial Orthop 2022;162:e183-e191)