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 coefficiency 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.