Purpose The range of impairments in children with neurodisability (ND) complicates data collection, yet individualising materials and procedures could enable more children to self-report. This study introduces the Cognitive Accessibility Tracking Questionnaire (CATQ), designed to monitor changes enhancing accessibility ("adaptations") in interview-administered patient-reported outcome measures (PROMs). The CATQ is used in a longitudinal study of mental health and participation in children with ND investigating adaptation use and its utility in assessing the risk of bias introduced by these adaptations.Materials and methodsThe 13-item CATQ was developed with experts in ND and augmentative and alternative communication. Predictors of PROM adaptations were analysed using linear regression; the overall change was tested with a t-test and item-specific agreement with Cohen's weighted kappa and proportion of agreement.ResultsSix interviewers conducted 69 interviews, interviewing 43 children once or twice. Common adaptations included explaining/replacing concepts (56.5% of interviews), exemplifying (60.9%), or repeating questions/instructions (50.7%). Child age, seizure history, verbal communication abilities, adaptive behaviour, and interviewer identity predicted adaptation use. Adaptation use did not differ between the two data collection points, 13 months apart.ConclusionThe CATQ enhances methodological rigor by tracking adaptations and facilitating risk-of-bias-assessment by analysing adaptation changes and factors affecting their use.