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

Abstract

Longitudinal cohort. To 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. The 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. We 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. A 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). Results 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.