Clinically Meaningful Improvement Following Cervical Spine Surgery: 30% Reduction Versus Absolute Point-change MCID Values

Abstract

Study Design. Retrospective analysis of prospectively collected registry data.Objective. The aim of this study was to compare the performance of 30% reduction to established absolute point-change values for measures of disability and pain in patients undergoing elective cervical spine surgery. Summary of Background Data. Recent studies recommend using a proportional change from baseline instead of an absolute point-change value to define minimum clinically important difference (MCID). Methods. Analyses included 13,179 patients who underwent cervical spine surgery for degenerative disease between April 2013 and February 2018. Participants completed a baseline and 12-month follow-up assessment that included questionnaires to assess disability (Neck Disability Index [NDI]), neck and arm pain (Numeric Rating Scale [NRS-NP/AP], and satisfaction [NASS scale]). Participants were classified as met or not met 30% reduction from baseline in each of the respective measures. The 30% reduction in scores at 12 months was compared to a wide range of established absolute point-change MCID values using receiver-operating characteristic curves, area under the receiver-operating characteristic curve (AUROC), and logistic regression analyses. These analyses were conducted for the entire patient cohort, as well as for subgroups based on baseline severity and surgical approach. Results. Thirty percent reduction in NDI and NRS-NP/AP scores predicted satisfaction with more accuracy than absolute point-change values for the total population and ACDF and posterior fusion procedures (P < 0.05). The largest AUROC differences, in favor of 30% reduction, were found for the lowest disability (ODI 0-20%: 16.8%) and bed-bound disability (ODI 81%-100%: 16.6%) categories. For pain, there was a 1.9% to 11% and 1.6% to 9.6% AUROC difference for no/mild neck and arm pain (NRS 0-4), respectively, in favor of a 30% reduction threshold. Conclusion. A 30% reduction from baseline is a valid method for determining MCID in disability and pain for patients undergoing cervical spine surgery.

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“…Alternatively, clinically meaningful change, which is represented by 30% improvement rather than a discrete value, can also demonstrate efficacy. 27…”

“…Alternatively, clinically meaningful change, which is represented by 30% improvement rather than a discrete value, can also demonstrate efficacy. 27 Considering VAS scores, MCID values of between 3.0 26 and 4.1 25 points have been suggested. Of the studies reporting discrete VAS scores, two report short-term outcomes greater than the upper estimate of the MCID, 21,23 one reports improvements that lie within the range of estimates, 18 and two report improvements less than the reported MCID for fusion surgery.…”

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“…There is no consensus on minimum important change in pain and disability or clinical success in patients undergoing ACDF. Therefore, we applied cutpoints of 30% improvement for minimum important change for pain and disability outcomes 31,32 and 50% improvement for clinical success for the disability outcome, 33 based on prior evidence for patients with lumbar spine disorders. Differences between trajectory subgroups in the proportion of patients meeting each clinical benchmark were examined with Fisher's exact test.…”

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“…Binary outcomes were 30% improvement from baseline at 3 and 12 months for ODI and NRS back/leg pain. Additional binary variables were patient satisfaction at 3 and 12 months (scores 1 and 2 were considered “satisfied,” scores 3 and 4 were considered “not satisfied”), return to work within 3 months, revision and readmission within 3 months, return to the odds ratio (OR) within 30 days, and presence of major and minor complications within 30 days 21. Return to work was only answered by patients who thought the question was applicable to them.…”