SRS-7: A valid, responsive, linear, and unidimensional functional outcome measure for operatively treated patients with AIS

Amit Jain, Paul D. Sponseller, Stefano Negrini, Peter O. Newton, Patrick J. Cahill, Tracey P. Bastrom, Michelle C. Marks

Research output: Contribution to journalArticlepeer-review

Abstract

Study Design. Comparison of the Scoliosis Research Society-22 (SRS-22) questionnaire with a 7-item Rasch-derived questionnaire (SRS-7). Objective. To compare the construct and discriminant validity, internal consistency, responsiveness, and dimensionality of SRS-7 against SRS-22 in operatively treated children with adolescent idiopathic scoliosis. Summary of Background Data. SRS-22 has not been shown to possess linearity or unidimensionality (internal validity). Methods. A multicenter database was queried for children with adolescent idiopathic scoliosis who underwent spinal fusion and answered all preoperative and 1-year postoperative SRS-22 questions. SRS-7 scores for the 685 patients were calculated from SRS-22 item responses. Traditional psychometric properties were assessed for both instruments (significance, P <0.01). Results. SRS-7 and SRS-22 scores correlated preoperatively and postoperatively (r = 0.78, P <0.001, and r = 0.78, P <0.001, respectively). Both instruments showed good discriminant validity in segregating 4 groups of patients with adolescent idiopathic scoliosis by curve magnitudes (F = 8.36, P <0.001, and F = 8.38, P <0.001, respectively). Pre- and postoperative SRS-7 and SRS-22 had internal consistency Cronbach α values of 0.64 and 0.67, and 0.85 and 0.85, respectively. With SRS-7, mean postsurgical improvement was 18.7 points (46.6-65.3, P <0.001), with effect size measures of Cohen d = 1.57, Hedge g = 1.57, and r = 0.62. With SRS-22, mean improvement was 11.6 points (84.5-96.1, P <0.01), with effect size measures of Cohen d = 1.25, Hedge g = 1.25, and r = 0.53. Iterative principal factor analysis of pre- and postoperative SRS-7 and SRS-22 showed the presence of 1 dominant latent factor (unidimensionality) and 4 latent factors (multidimensionality), respectively. Conclusion. SRS-7 shows good concurrent and discriminative validity, reasonable internal consistency, and excellent responsiveness. It has the advantages over SRS-22 of being short, unidimensional, and an interval scale.

Original languageEnglish
Pages (from-to)650-655
Number of pages6
JournalSpine
Volume40
Issue number9
DOIs
Publication statusPublished - May 1 2015

Keywords

  • adolescent idiopathic scoliosis
  • health-related quality of life
  • Scoliosis Research Society questionnaire

ASJC Scopus subject areas

  • Clinical Neurology
  • Orthopedics and Sports Medicine

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