Minimum Clinically Important Difference

Study Design. Review of the 2011 to 2015 minimum clinically important difference (MCID)-related publications in Spine, Spine Journal, Journal of Neurosurgery-Spine, and European Spine Journal. Objective. To summarize the various determinations of MCID and to analyze its usage in the spine literature of the past 5 years in order to develop a basic reference to help practitioners interpret or utilize MCID. Summary of Background Data. MCID represents the smallest change in a domain of interest that is considered beneficial to a patient or clinician. The many sources of variation in calculated MCID values and inconsistency in its utilization have resulted in confusion in the interpretation and use of MCID. Methods. All articles from 2011 to 2015 were reviewed. Only clinical science articles utilizing patient reported outcome scores (PROs) were included in the analysis. A keyword search was then performed to identify articles that used MCID. MCID utilization in the selected papers was characterized and recorded. Results. MCID was referenced in 264/1591 (16.6%) clinical science articles that utilized PROs: 22/264 (8.3%) independently calculated MCID values and 156/264 (59.1%) used previously published MCID values as a gauge of their own results. Despite similar calculation methods, there was a two- or three-fold range in the recommended MCID values for the same instrument. Half the studies recommended MCID values within the measurement error. Most studies (97.2%) using MCID to evaluate their own results relied on generic MCID. The few studies using specific MCID (MCID calculated for narrowly defined indications or treatments) did not consistently match the characteristics of their sample to the specificity of the MCID. About 48% of the studies compared group averages instead of individual scores to the MCID threshold. Conclusion. Despite a clear interest in MCID as a measure of patient improvement, its current developments and uses have been inconsistent. Level of Evidence: N/A