Measuring Quality of Life in Adults with Scoliosis: A Cross-Sectional Study Comparing SRS-22 and ISYQOL Questionnaires.

Idiopathic scoliosis is common in adulthood and can impact patients' physical and psychological health. The Scoliosis Research Society-22 Questionnaire (SRS-22) has been designed to assess health-related quality of life (HRQOL) in idiopathic scoliosis, and it is the most used disease-specific outcome tool from adolescence to adulthood. More recently, the Italian Spine Youth Quality of Life (ISYQOL) international questionnaire was developed, which performs better than SRS-22 in adolescent spinal deformities. However, the ISYQOL questionnaire has never been tested in adults. This study compares the construct validity of ISYQOL and SRS-22 with the Rasch analysis (partial credit model). We recruited 150 adults and 50 adolescents with scoliosis (≥30° Cobb). SRS-22, but not ISQYOL, showed disordered categories and one item not fitting the Rasch model. A 21-item SRS-22 version with revised categories was arranged and further compared to ISYQOL. Both questionnaires showed multidimensionality, and some items (SRS-22 in a greater number) functioned differently in persons of different ages. However, the artefacts caused by multidimensionality and differential functioning had a low impact on the questionnaires' measures. The construct validity of ISYQOL International and the revised SRS-22 are comparable. Both questionnaires (but not the original SRS-22) can return measures of disease burden in adults with scoliosis.