Repeatability, Reliability, and Concurrent Validity of the Scoliosis Research Society-22 Questionnaire and EuroQol in Patients With Adolescent Idiopathic Scoliosis

Study Design. Cross-sectional study in patients with adolescent idiopathic scoliosis (AIS). Objectives. To evaluate the repeatability, reliability, internal consistency, and concurrent validity (CD) of an adapted Norwegian version of the Scoliosis Research Society 22 questionnaire (SRS-22) and the generic health-related quality of life instrument EuroQol (EQ-5D and EQ-VAS). Summary of Background Data. SRS-22 is widely used for evaluation of health-related quality of life in AIS. Its repeatability, which is essential for use in follow-up studies, and CD with EuroQol which can be used for cost-utility analysis, has not yet been assessed. Methods. The forward-backward translation of the English version of the SRS-22 was performed according to guidelines for cross-cultural adaptation of outcome questionnaires. Fifty-seven patients of various ages with AIS and deformity severity filled out standardized questionnaires: SRS-22, EQ-5D, and EQ-VAS, each twice in a 2-week interval. The study was approved by the Regional Ethics Committee for Medical Research in Norway. Results. There were no floor or ceiling effects on the score distributions. The study demonstrated moderate internal consistency and high reliability of SRS-22 questionnaire with Chronbach alpha and intraclass correlation co-efficiency ranging from 0.76 to 0.93 for the 5 domains. Repeatability was excellent for all SRS-22 domains with repeatability coefficients < 1. CD with EQ-5D was poor to moderate with Pearson's r ranging from 0.14 to 0.58. However, total scores of the 2 instruments showed satisfactory agreement. Conclusion. The SRS-22 outcome instrument has satisfactory repeatability, but CD with EQ-5D suggests that the disease-specific and the generic questionnaire measure different constructs.