Minimal Important Difference in Patient Reported Outcome Measures in Persons with Severe Mental Illness, a Post-hoc Pre-Post Analysis
Abstract Background: Complementary interventions for persons with severe mental illness (SMI) provide broad strategies for recovery and illness self-management. It is not known which outcome measure can be considered to be relevant for persons with SMI. This knowledge can motivate a professional to offer and stimulate a person to participate in that intervention. This paper aimed to identify the outcome measures that determine the most relevant and meaningful change and capture the benefits of a complementary intervention. Methods: By using anchor-based and distribution-based methods, we estimated the minimal important difference (MID) to determine which outcome measure persons improved in beyond the MID to reflect a relevant change in pre-post effect of a complementary intervention, in casu the Illness Management and Recovery programme (IMR).Results: The anchor MID was based on the results of the measure Rand General Health Perception (Rand-GHP). On all MIDs, the Mental Health Recovery Measure (MHRM) had the highest score on the effect compared to its MIDs, and also on all MIDs the MHRM had the highest percentages of participants that scored above the MID. Conclusion: The Rand-GHP is considered to be an excellent measure for investigating the MID as a result of an intervention. The results of our study can be used in shared decision-making processes to determine which intervention is suitable for a person with SMI. A person who desires a recovery outcome, as measured by the MHRM, can be recommended to do the IMR programme.