Background: Though the concept of MCID (minimum clinically important difference) as a measurement of surgical outcome has been extensively studied, there is lack of consensus on the most valid or clinically relevant MCID calculation approach.
Objective: To compare the range of MCID threshold values obtained by different anchor-based and distribution-based approaches in order to determine the best clinically meaningful and statistically significant MCID for our studied group.
Methods: 88 consecutive patients undergoing surgery for subaxial degenerative cervical spine disease were analyzed from a prospective blinded database. Preoperative, 3- and 6-months postoperative Patient Reported Outcome (PRO) scores and blinded surgeon ratings were collected. Four calculation methods were used to calculate MCID threshold values: average change, change difference, minimum detectable change (MDC), and receiver operating characteristic curve (ROC). Three anchors were used to evaluate meaningful improvement post-surgery: HTI (Health Transition Item), Patient Overall Status, and Surgeon Ratings.
Results: On average, all patients had a statistically significant improvement (p<0.001) postoperatively for NDI (neck disability index) (score 27.42 preoperatively to 19.42 postoperatively), PCS (physical component of the SF-36) (33.02 to 42.23), MCS (mental component of the SF-36) (44 to 50.74) and VAS (visual analog scale) (2.85 to 1.93). The four MCID approaches yielded a range of values for each PRO: 2.23-16.59 for PCS, 0.11-16.27 for MCS and 2.72-12.08 for NDI. When compared to HTI and Patient Overall Status anchors, the area under the ROC curve was consistently greater for Surgeon Ratings for all four PROs.
Conclusion: MDC together with Surgeon Ratings anchor appears to be the most appropriate MCID method. Based on our findings, this combination offers the greatest area under the ROC curve (threshold above the 95% CI). The choice of the anchor did not significantly affect this result.
From: Measuring Surgical Outcomes in Subaxial Degenerative Cervical Spine Disease Patients: Minimum Clinically Important Difference as a Tool for Determining Meaningful Clinical Improvement by Auffinger et al.