title: Determining the minimal clinically important difference criteria for the Multidimensional Fatigue Inventory in a radiotherapy population.
abstract: OBJECTIVE
  The Multidimensional Fatigue Inventory (MFI) is a commonly used cancer-related fatigue assessment tool. Unlike other fatigue assessments, there are no published minimal clinically important difference (MCID) criteria for the MFI in cancer populations. MCID criteria determine the smallest change in scores that can be regarded as important, allowing clinicians and researchers to interpret the meaning of changes in patient's fatigue scores. This research aims to improve the clinical utility of the MFI by establishing MCID criteria for the MFI sub-scales in a radiotherapy population.
  
  
  METHODS
  Two hundred ten patients undergoing radiotherapy were recruited to a single-centre prospective cohort study. Patients were assessed at three time points, at the start of radiotherapy, the end of radiotherapy and 6 weeks after radiotherapy completion. Assessment consisted of four clinically relevant constructs: (1) treatment impact on fatigue, (2) health-related quality of life, (3) performance status and (4) occupational productivity. These constructs were used as external or anchor-based measures to determine MCIDs for each sub-scale of the MFI.
  
  
  RESULTS
  Multiple MCIDs were identified, each from a different perspective based on the constructs cited. Researchers seeking to use a generic MCID may wish to use a two-point reference for each MFI sub-scale as it was consistent across the pre- and post-radiotherapy comparison and occupational productivity anchors.
  
  
  CONCLUSIONS
  MCIDs validated in this study allow better interpretation of changes in MFI sub-scale scores and allow effect size calculations for determining sample size in future studies.
authors.affiliation: School of Health and Rehabilitation Sciences, The Univeristy of Queensland, St Lucia, Brisbane 4067, Australia. amanda.purcell@uqconnect.edu.au
authors.forename: Amanda
authors.initials: A
authors.lastname: Purcell
authors.forename: Jennifer
authors.initials: J
authors.lastname: Fleming
authors.forename: Sally
authors.initials: S
authors.lastname: Bennett
authors.forename: Bryan
authors.initials: B
authors.lastname: Burmeister
authors.forename: Terry
authors.initials: T
authors.lastname: Haines
mesh_terms: D015331:Cohort Studies; D004651:Employment; D005221:Fatigue / Q000145:classification* / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000532:radiotherapy; D011446:Prospective Studies; D011788:Quality of Life; D011878:Radiotherapy / Q000009:adverse effects*