The quality of spine surgery from the patient’s perspective: Part 2. Minimal clinically important difference for improvement and deterioration as measured with the Core Outcome Measures Index

Abstract

The Core Outcome Measures Index (COMI) is a reliable and valid instrument for assessing multidimensional outcome in spine surgery. The minimal clinically important score-difference (MCID) for improvement (MCID imp ) was determined in one of the original research studies validating the instrument, but has never been confirmed in routine clinical practice. Further, the MCID for deterioration (MCID det ) has never been investigated; indeed, this needs very large sample sizes to obtain sufficient cases with worsening. This study examined the MCIDs of the COMI in routine clinical practice. All patients undergoing surgery in our Spine Center since February 2004 were asked to complete the COMI before and 12 months after surgery. The COMI has one question each on back (neck) pain intensity, leg/buttock (arm/shoulder) pain intensity, function, symptom-specific well-being, general quality of life, work disability, and social disability, scored as a 0-10 index. At follow-up, patients also rated the global effectiveness of surgery, on a 5-point Likert scale. This was used as the external criterion (''anchor'') in receiver operating characteristics (ROC) analyses to derive cut-off scores for individual improvement and deterioration. Twelve-month follow-up questionnaires were returned by 3,056 (92%) patients. The group mean COMI score change for patients declaring that the ''operation helped'' was a reduction of 3.1 points; the corresponding value for those whom it ''did not help'' was a reduction of 0.5 points. The group MCID imp was hence 2.6 points reduction; the corresponding group MCID det was 1.2 points increase (0.5 minus -0.7). The area under the ROC curve was 0.88 for MCID imp and 0.89 for MCID det (both P \ 0.0001), indicating that the COMI had good discriminative ability. The cut-offs for individual improvement and deterioration, respectively, were C2.2 points decrease (sensitivity 81%, specificity 83%) and C0.3 points increase (sensitivity 83%, specificity 88%). The MCID imp score of 2.2 points was similar to that reported in the original study (2-3 points, depending on external criterion used). The MCID det suggested that the COMI is less responsive to deterioration than to improvement, a phenomenon also reported for other spine outcome instruments. This needs further investigation in even larger patient groups. The MCIDs provide essential information for both the planning (sample size) and interpretation of the results (clinical relevance) of future clinical studies using the COMI.

Criteria for failure and worsening after surgery for lumbar disc herniation: a multicenter observational study based on data from the Norwegian Registry for Spine Surgery

“…For instance, severely disabled patients will require disproportionally greater improvements than the less disabled, not to consider the surgery as failed. This is in accordance with findings of other studies and illustrates the importance of taking into account the baseline score while interpreting PROM change scores, regardless of using absolute or percentage change scores [18,41]. Consequently, one should adjust for the baseline score when using such outcome criteria in clinical trials and risk factor analyses.…”

“…When informing the patient about possible outcomes, we think that it is important to differentiate between being unchanged after surgery, which might be an acceptable risk, and actually getting worse, which might be harmful. Previous studies show that larger cohorts are needed to clearly define clinically meaningful thresholds for such outcomes, especially for worsening [17,18].…”

Cross-cultural adaptation and validation of the Polish version of the Core Outcome Measures Index for low back pain

“…Similar values were reported for other language versions (French 1.98 [12], German 1.74 [8], Italian 1.51 [1], Norwegian 2.21 [14], Brazilian-Portuguese 1.66 [13]). Based on the previous studies, the estimated minimal clinically important difference for the overall COMI score is between 2 and 3 points [8,10,15]. If such range was assumed for a Polish version, these values are significantly greater than 1.79, thus, making it a suitable clinical tool.…”

“…COMI is a relatively short self-administered multidimensional questionnaire intended to assess the influence of LBP on several domains of everyday life. The psychometric properties of COMI have been assessed by several independent research groups [6][7][8][9][10], proving it to be a valid and highly responsive instrument. It has been adapted and validated for the use in German [8,11], Spanish [7], French [12], Italian [1], Brazilian-Portuguese [13] and Norwegian [14] versions.…”

Case Reports: Anteroinferior Acetabular Rim Damage Due to Femoroacetabular Impingement

“…(helped a lot, helped, helped only a little, didn't help, made things worse) [12,22] (Table 3). Validated preoperative outcomes data were not available for comparison.…”