Cultural Variations in the Minimum Clinically Important Difference Thresholds for SRS-22R After Surgery for Adult Spinal Deformity

Abstract

Study DesignLongitudinal cohort. ObjectiveTo calculate the minimum clinically important difference (MCID) threshold values for the Scoliosis Research Society–22R (SRS-22R) in Japanese patients with adult spinal deformity (ASD) and to compare the results with previously reported values in a North American population. Summary of Background DataThe SRS-22R has been shown to be reliable, valid, and responsive to change in patients with ASD undergoing surgery. The MCID quantifies a threshold value of improvement that is clinically relevant to the patient. We hypothesize that MCID threshold values of SRS-22R differ between different cultural groups. MethodsWe identified ASD patients who completed the SRS-22R preoperatively and the SRS-30 at minimum two years after surgery. Answers to the last seven questions of the SRS-30 were used as anchors to determine the MCID for the SRS-22R Activity, Pain, Appearance, Mental domains, and Total score using receiver operating characteristic (ROC) curve analysis. ResultsA total of 122 (16 male, 106 female) patients were included in the analysis. There was a statistically significant improvement in all domain scores from preoperation to two years postoperation. There was a statistically significant difference in change in domain score among the responses to the anchors (p < .05). The ROC curve analysis yielded MCID values of 0.90 for Activity (area under the curve [AUC] = 0.766), 0.85 for Pain (AUC = 0.637), 1.05 for Appearance (AUC = 0.764), and 0.70 for Mental (AUC = 0.641) domain, 1.05 for Total score (AUC = 0.670). Except for Appearance, these MCID thresholds were higher compared with values reported in patients from North America (Activity = 0.60, Pain = 0.40, Appearance = 1.23, Total = 0.71). ConclusionsResults of this study showed that cultural variations exist for MCID threshold values for SRS-22 Activity, Pain, Mental domains, and Total score after surgical treatment of ASD.