The Minimum Clinically Important Difference in Scoliosis Research Society-22 Appearance, Activity, and Pain Domains After Surgical Correction of Adolescent Idiopathic Scoliosis

Study Design. Longitudinal cohort. Objective. To determine the minimum clinically important difference (MCID) of the Scoliosis Research Society (SRS)-22 Appearance, Activity, and Pain domains in patients with adolescent idiopathic scoliosis undergoing surgical correction of their spinal deformity. Summary of Background Data. The MCID, a threshold of improvement that is clinically relevant to the individual patient, is increasingly used to evaluate treatment effectiveness. MCID values for the SRS-22 domains have not been determined. Methods. Patients with adolescent idiopathic scoliosis who underwent surgical correction and had completed SRS-22 before operation and the SRS-30 and Scoliosis Appearance Questionnaire (SAQ) at 1 year after operation from a multicenter database for pediatric scoliosis were identified. The SAQ is a modification of the Walter Reed Visual Assessment Scale and is used to assess the patient's perception of their spinal deformity. Paired sample t tests were used to compare preoperative and 1-year postoperative scores. Spearman correlations were used to evaluate associations between domain scores and summed responses to anchors for Appearance, Activity, and Pain. MCID values for the SRS-22 domains were determined using receiver operating characteristic curve analysis, with summed responses to anchor questions 23 to 30 of the SRS-30 and items 26 and 32 of the SAQ. Results. There were 735 women and 152 men with a mean age of 14.3 years and a mean Cobb angle of 53. There was a statistically significant difference between paired preoperative and 1-year SRS domain scores. Analysis of variance showed a statistically significant difference between the summed responses to the anchors. The MCID was 0.20 for the Pain domain (area under the curve [AUC] = 0.723), 0.08 for Activity (AUC = 0.648), and 0.98 for Appearance (AUC = 0.629). The MCID for activity was less than the standard error of measurement. Conclusion. The MCID for the Pain domain was 0.20 and 0.98 for Appearance. Because these patients were generally in good health, a minimal though significant change in activity was observed, such that the calculated MCID was within the measurement error. As expected, the largest and most important change was in the Appearance domain. Future studies are needed to determine the MCID for the mental domain and the total SRS score and to further validate the MCID values in this study.