Estimation of the minimal clinically important difference on the Aberrant Behaviour Checklist-Irritability (ABC-I) for people with intellectual disabilities who display aggressive challenging behaviour: A triangulated approach.

BACKGROUND: The minimal clinically important difference (MCID) is relevant in the estimation of improvement in a patient outcome. AIM: To determine the MCID on the Aberrant Behaviour Checklist-Irritability (ABC-I), widely used to measure the effects of intervention for aggressive challenging behaviour in people with intellectual disabilities. METHOD AND PROCEDURES: We utilised distribution and anchor based methods to estimate the ABC-I MCID. We extracted data from 15 randomised controlled trials (RCTs) for meta-analysis. We conducted three online workshops with family carers and professionals to consider meaningful change in case vignettes of increasing severity of aggressive challenging behaviour. OUTCOMES AND RESULTS: We did not find overlap in the range of values between the two approaches. The meta-analysis indicated a range of MCID on the ABC-I (0.05, 4.94) whilst the anchor-based estimation indicated a larger change (6.6, 16.6). CONCLUSIONS AND IMPLICATIONS: The MCID is essential in interpreting the results from intervention studies. The present work was undertaken as part of a wider programme on the development and testing of a psychosocial intervention for aggressive challenging behaviour, and it is of interest to researchers in justifying how they choose and determine the MCID on the outcome of interest.