Determination of the minimal clinically important difference on the Australian Therapy Outcome Measures for occupational therapy (AusTOMs – OT)

Purpose: Outcome measures must be responsive to change (able to show statistically significant change) and must also produce information on the degree of change that is clinically significant, or the minimal clinically important difference (MCID). This research sought to establish the MCID for four domains of the Australian Therapy Outcome Measures for Occupational Therapy (AusTOMs – OT). Methods: Using a criterion approach, 30 international clinicians were surveyed about their perceptions of the MCID for AusTOMs – OT. Second, using a distribution-based approach, the MCID was calculated as half of the standard deviation (SD) of the AusTOMs – OT raw scores for a sample of 787 clients. Results: Just over half the clinicians surveyed indicated that a one-point change represented the MCID for AusTOMs – OT for three domains, and 0.5-point change showed MCID for the final domain. The data analysed for the distribution-based calculation indicated that the half SD ranged from 0.51 to 0.61. Conclusion: Using both criterion and distribution-based approaches, this research empirically demonstrated that a change on the four domains of the AusTOMs – OT of between 0.51 and 1 point shows MCID. Considering these findings, and for ease of clinical interpretation, it is recommended that a one-point shift be adopted as the MCID across all domains.