Psychometric analysis and the implications for the use of the scoliosis research society questionnaire (SRS-22r English) for individuals with adolescent idiopathic scoliosis

Background: Despite widespread usage of the SRS-22r questionnaire (Scoliosis Research Society Questionnaire 22r), the English version has only sparingly been subjected to analysis using modern psychometric techniques for patients with adolescent idiopathic scoliosis (AIS). The study purpose was to improve interpretation and clinical utility of the SRS-22r for adolescents with AIS by generating additional robust evidence, using modern statistical techniques. Questions about (1) Structure and (2) Item and Scale Functioning are addressed and interpreted for clinicians and researchers. Methods: This retrospective case review analyzed SRS-22r data collected from 1823 patients (mean age 14.9 +/- 2.2years) with a primary diagnosis of AIS who clinically completed an SRS-22r questionnaire. Individual SRS-22r questions and domain scores were retrieved through data queries. Patient information collected through chart review included diagnosis, age at assessment, sex, race and radiographic parameters. From 6044 SRS-22r assessments, 1 assessment per patient was randomly selected. Exploratory structural equation modeling (ESEM) and item response theory (IRT) techniques were used for data modeling, item calibration, and reliability assessment. Results: ESEM demonstrated acceptable fit to the data: chi(2) (130) = 343.73, p < .001; RMSEA = 0.035; CFI = 0.98; TLI = 0.96; SRMR = 0.02. Several items failed to adequately load onto their assigned factor. Item fit was adequate for all items except SRSq10 (Self-Image), SRSq16 (Mental Health), and SRSq20 (Mental Health). IRT models found item discriminations are within normal levels for items in psychological measures, except items SRSq1 (pain), SRSq2 (pain), and SRSq16 (mental health). Estimated reliability of the Function domain ( rho= 0.69) was low, however, Pain, Self-Image and Mental Health domains exhibited high ( rho> 0.80) reliability. Conclusions: Modern psychometric assessment of the SRS-22r, in adolescent patients with AIS, are presented and interpreted to assist clinicians and researchers in understanding its strengths and limitations. Overall, the SRS-22r demonstrated good psychometric properties in all domains except function. Cautious interpretation of the total score is suggested, as it does not reflect a single HRQoL construct.