Refinement of the SRS-22 Health-Related Quality of Life questionnaire Function domain

Abstract

Study design: Prospective observational case series.

Objectives: To improve the Scoliosis Research Society-22 (SRS-22) Health-Related Quality of Life (HRQL) questionnaire Function domain internal consistency for patients younger than 18 years.

Summary of background data: During English validation as well as Spanish and Turkish transcultural adaptation studies, low internal consistency of the Function domain was discovered for patients younger than 18 years. The problem was traced to questions 15 (relating to financial considerations) and 18 (relating to going out with friends). Otherwise, the SRS-22 HRQL questionnaire has been shown to be valid and has been successfully translated into Spanish and Turkish.

Methods: Based on existing data, question 18's stem and responses were revised without changing its content and added to the SRS-22 questionnaire. Question 15 remained unchanged, and the effect of inclusion or exclusion on domain score was determined. During a 3-month period, the questionnaire was completed by 111 outpatients, including four groups: idiopathic scoliosis age < 18 years (n = 37), idiopathic scoliosis age > or = 18 years (n = 32), other spinal disorders age < 18 years (n = 17), and other spinal disorders age > or = 18 years (n = 25).

Results: As a result of the revision of question 18, the Function domain internal consistency, Cronbach's alpha, for patients age <18 years was increased from 0.67 to 0.78 for patients with idiopathic scoliosis and from 0.60 to 0.80 for patients with other spinal disorders. Domain internal consistency remained high, 0.77 to 0.96 for all the other domain-patient groupings. Removal of question 15 slightly improved Function domain internal consistency for idiopathic scoliosis patients < 18 years old and slightly decreased it for patients < 18 years old with other spinal conditions.

Conclusion: With a minor revision of question 18 (related to going out) the internal consistency of the SRS-22 Function domain has been improved in idiopathic scoliosis patients < 18 years of age. Deletion of question 15 (related to financial considerations) has a variable, small effect depending on patient group. Retention of question 15 is recommended unless a cultural variable, such as differences in healthcare payment schemes, substantially lowers domain psychometric properties.