title: Relative utility of a visual analogue scale vs. a six-point Likert scale in the measurement of global subject outcome in patients with low back pain receiving physiotherapy.
abstract: BACKGROUND
  Patients' subjective impression of change is an important construct to measure following physiotherapy, but little evidence exists about the best type of measure to use.
  
  
  OBJECTIVE
  To compare the construct validity and utility of two forms of a global subjective outcome scale (GSOS) in patients with back pain: Likert and visual analogue scale (VAS) GSOS.
  
  
  METHODS
  Two samples of patients attending physiotherapy for back pain completed a questionnaire battery at discharge from physiotherapy including either a Likert or VAS GSOS.
  
  
  METHODS
  One hundred and eighty-seven {79 males, mean age 52.1 [standard deviation (SD) 15.5] years} patients completed the Likert GSOS and a separate sample of 144 patients [62 males, mean age 55.7 (SD 15.9) years] completed the VAS GSOS upon discharge from physiotherapy.
  The two versions of the GSOS were compared using pre- and post-treatment changes in scores using a VAS (pain), Roland-Morris Disability Questionnaire (18-item version) and catastrophising subscale of the Coping Strategies Questionnaire 24.
  
  
  RESULTS
  Both versions of the GSOS showed significant (P<0.01) moderate correlations (r between 0.30 and 0.46) with changes in pain and disability. The correlations between the two types of GSOS and changes in catastrophising were trivial and not significant (Likert GSOS: r=0.07, P=0.372; VAS GSOS: r=0.10, P=0.267). There were fewer missing values in the Likert GSOS (1%) compared with the VAS GSOS (8%).
  
  
  CONCLUSIONS
  The two versions of the GSOS showed similar validity; however, use of the Likert GSOS is recommended because of its greater utility.
authors.affiliation: School of Health and Social Care, University of Teesside, Middlesbrough, UK. Electronic address: Nick.Harland@nhs.net.
authors.forename: N J
authors.initials: NJ
authors.lastname: Harland
authors.affiliation: Spinal Rehabilitation Unit, Physiotherapy Department, Friarage Hospital, Northallerton, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Dawkin
authors.affiliation: School of Health and Social Care, University of Teesside, Middlesbrough, UK.
authors.forename: D
authors.initials: D
authors.lastname: Martin
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis* / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D010147:Pain Measurement / Q000295:instrumentation* / Q000379:methods; D017060:Patient Satisfaction / Q000706:statistics & numerical data*; D026741:Physical Therapy Modalities; D015203:Reproducibility of Results; D018570:Risk Assessment; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D064232:Visual Analog Scale
keywords: Back pain; Global subjective outcome; Likert scale; Visual analogue scale