Construction and validation of the scoliosis quality of life index in adolescent idiopathic scoliosis

Abstract

Study design: A prospective cross-sectional design was used to evaluate the Scoliosis Quality of Life Index (SQLI). SQLI is a 22-item self-reporting health-related quality-of-life questionnaire for idiopathic scoliosis patients.

Objective: The goal of this study was to evaluate the psychometric qualities of SQLI.

Summary of background data: SQLI, a modification of the Scoliosis Research Society-22 (SRS-22) questionnaire, is intended to be more applicable to patients with adolescent idiopathic scoliosis (AIS) between 10 and 18 years of age.

Methods: Eighty-four subjects with a mean age of 14.9 years participated. We determined reliability, validity, distribution of scores, and clinical utility of SQLI in a hospital setting. Seventy patients were AIS patients (16 postsurgical, 30 braced, 24 unbraced) with a mean Cobb angle of 30.7 degrees, and 14 patients were sibling controls.

Results: Reliability: Intraclass correlation coefficient for test-retest reliability of the global index was very good (ICC 2,1 = 0.80); Spearman's rho correlations between items and domains was 0.39 to 0.89 and between domains and global index was 0.55 to 0.78; Cronbach's alpha scores were more than 0.80 (0.82-0.89).

Validity: construct validity was established by correlations between SQLI's global index and Quality of Life Profile for Spine Deformities (QLPSD) global index (Spearman's rho, 0.79) and between SQLI domains and QLPSD domains (0.46-0.81); discriminate validity was established by SQLI's global index successfully partitioned controls and AIS subjects (Kruskal-Wallis test, P = 0.0013). Time required by the patient averaged 2.5 minutes per administration.

Conclusions: SQLI is reliable and valid and demonstrates satisfactory distribution of scores. SQLI is a promising instrument in the assessment of AIS patients.