title: Simplifying outcome measurement: evaluation of instruments for measuring outcome after fusion surgery for chronic low back pain.
abstract: METHODS
  A comparative evaluation of outcome instruments and global assessment was performed.
  
  
  OBJECTIVE
  To test patient global assessment as a substitute for the use of more comprehensive outcome instruments in treatment trials of chronic low back pain.
  
  
  BACKGROUND
  Treatment outcome can be measured with pain scales and functional instruments. In the absence of a gold standard, the patient him- or herself is the basic reference for outcome, for which the instruments give a more or less exact measurement. Global assessment, which is a retrospective recording, may overestimate improvement as a result of recall or motivational bias.
  
  
  METHODS
  In this study, 294 patients treated for chronic low back pain were evaluated with a visual analog scale for back pain, the Oswestry Disability Index, the Million Score and general function score for disease-specific disability, and the Zung Depression Scale for depressive symptoms. The correlation between the pretreatment and posttreatment scores for the outcome instruments (Delta scores) and the global assessment scores was calculated; effect sizes were compared; sensitivity and specificity with receiver operating characteristics (ROC) curves were estimated; and associations of global assessment with pretreatment and posttreatment scores were determined.
  
  
  RESULTS
  All the Delta scores showed significant correlations with patient global assessment and with each other. The effect size of global assessment tended to be greater than that of the outcome instruments. The specificity and sensitivity of the disability instruments and pain scale were approximately 75%, whereas they were lower for depression. The associations between global assessment and outcome instrument scores did not produce evidence that global assessment was biased.
  
  
  CONCLUSIONS
  Patient global assessment is a valid and responsive descriptor of overall effect in randomized controlled trials of treatment for chronic low back pain.
authors.affiliation: Department of Orthopedics, Sahlgren University Hospital, Gothenburg, Sweden. ollehagg@hotmail.com
authors.forename: Olle
authors.initials: O
authors.lastname: Hägg
authors.forename: Peter
authors.initials: P
authors.lastname: Fritzell
authors.forename: Anders
authors.initials: A
authors.lastname: Odén
authors.forename: Anders
authors.initials: A
authors.lastname: Nordwall
mesh_terms: D002908:Chronic Disease; D003863:Depression / Q000175:diagnosis; D004185:Disability Evaluation; D006304:Health Status; D006801:Humans; D016014:Linear Models; D017116:Low Back Pain / Q000601:surgery*; D010147:Pain Measurement; D011237:Predictive Value of Tests; D012372:ROC Curve; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013123:Spinal Fusion; D016896:Treatment Outcome