title: Patients' ratings of global perceived change during 2 years were strongly influenced by the current health status.
abstract: OBJECTIVE
  To investigate the longitudinal validity of patients' ratings of global perceived change (GPC) and to assess the implications of using the GPC as the anchor to determine the minimal important change (MIC).
  
  
  METHODS
  Secondary analysis of data from a multicenter study including 380 patients with disc-related sciatica with follow-ups at 3, 6, 12, and 24 months. The GPC scale ranged from much worse to completely gone. Five patient-reported outcome measures were used. An MIC was defined as the mean change score in the actual outcome measure for patients reporting being better. The influence of patients' current state and baseline scores on the GPC was analyzed by multivariate linear regression. Differences in the magnitude of the MIC between the 3- and 24-month recall periods were analyzed by hierarchical linear models.
  
  
  RESULTS
  Across all recall periods and outcome measures, the GPC was strongly influenced by the patient's state at the time of asking. In four of five outcome measures, the magnitude of the MIC increased when recall increased from 3 to 24 months.
  
  
  CONCLUSIONS
  Caution is needed when using the GPC to determine the MIC of patient-reported outcome measures in patients with chronic conditions.
authors.affiliation: Department of Rheumatology, Sykehuset Østfold, 1603 Fredrikstad, Norway. Electronic address: largro@so-hf.no.
authors.forename: Lars
authors.initials: L
authors.lastname: Grøvle
authors.affiliation: Department of Rheumatology, Sykehuset Østfold, 1603 Fredrikstad, Norway.
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Haugen
authors.affiliation: Department of Physiotherapy, Sykehuset Østfold, 1603 Fredrikstad, Norway; National Institute of Occupational Health, 0033 Oslo, Norway.
authors.forename: Eivind
authors.initials: E
authors.lastname: Hasvik
authors.affiliation: Department of General Practice, Institute of Health and Society, University of Oslo, 0316 Oslo, Norway.
authors.forename: Bård
authors.initials: B
authors.lastname: Natvig
authors.affiliation: Department of Physical Medicine and Rehabilitation, Oslo University Hospital, 0424 Oslo, Norway.
authors.forename: Jens I
authors.initials: JI
authors.lastname: Brox
authors.affiliation: FORMI (Communication Unit for Musculoskeletal Disorders), Division of Neuroscience, Oslo University Hospital, Ullevaal, 0424 Oslo, Norway; Department of Physiotherapy, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, 0130 Oslo, Norway.
authors.forename: Margreth
authors.initials: M
authors.lastname: Grotle
mesh_terms: D059026:Diagnostic Self Evaluation; D005500:Follow-Up Studies; D006304:Health Status; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000150:complications / Q000628:therapy*; D007405:Intervertebral Disc Displacement / Q000150:complications / Q000628:therapy*; D016014:Linear Models; D011939:Mental Recall; D015999:Multivariate Analysis; D015203:Reproducibility of Results; D012585:Sciatica / Q000209:etiology / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome
keywords: Global perceived change; Minimal clinically important difference; Minimal important change; Outcome assessment; Recall bias; Transition rating