title: SRS-7: A Valid, Responsive, Linear, and Unidimensional Functional Outcome Measure for Operatively Treated Patients With AIS.
abstract: METHODS
  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.
  
  
  BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
  
  
  METHODS
  4.
authors.affiliation: *Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, MD †Clinical and Experimental Sciences Department, University of Brescia, Brescia, Italy ‡IRCCS Fondazione Don Gnocchi, Milan, Italy §Department of Orthopedics, Rady Children's Hospital of San Diego, CA; and ¶Department of Orthopaedic Surgery, Shriners Hospitals for Children, Philadelphia, PA.
authors.forename: Amit
authors.initials: A
authors.lastname: Jain
authors.forename: Paul D
authors.initials: PD
authors.lastname: Sponseller
authors.forename: Stefano
authors.initials: S
authors.lastname: Negrini
authors.forename: Peter O
authors.initials: PO
authors.lastname: Newton
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cahill
authors.forename: Tracey P
authors.initials: TP
authors.lastname: Bastrom
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Marks
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D011788:Quality of Life; D012189:Retrospective Studies; D012600:Scoliosis / Q000453:epidemiology / Q000601:surgery*; D011795:Surveys and Questionnaires