title: Three ways to quantify uncertainty in individually applied "minimally important change" values.
abstract: OBJECTIVE
  Determining "minimally important change" (MIC) facilitates the interpretation of change scores on multi-item instruments. This article focuses on how MIC values should be interpreted when applied to individual patients.
  
  
  METHODS
  The MIC value of a hypothetical questionnaire "Q" was determined in a sample of 400 patients who improved and 100 patients who did not improve, using the receiver operating characteristic (ROC) method, and three methods to quantify the uncertainty.
  
  
  RESULTS
  The MIC value on questionnaire Q was 10.5. Firstly, the 95% confidence interval (CI) of the MIC value (for questionnaire Q: 5.6-14.2) quantifies the uncertainty of the estimation of the MIC value. Secondly, "how sure we are that this MIC value holds for every patient" is quantified by the values for sensitivity (74%) and specificity (91%). Thirdly, the smallest detectable change (SDC) on questionnaire Q is calculated (16.0) to consider whether the MIC value (10.5) falls outside or within the measurement error.
  
  
  CONCLUSIONS
  For application in clinical research and practice, MIC values are always considered at the individual level, but determined in groups of patients. The interpretation comes with different forms of uncertainty. To appreciate the uncertainty, knowledge of the underlying distributions of change scores is indispensable.
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, 1081 BT Amsterdam, The Netherlands. hcw.devet@vumc.nl
authors.forename: Henrica C W
authors.initials: HC
authors.lastname: de Vet
authors.forename: Berend
authors.initials: B
authors.lastname: Terluin
authors.forename: Dirk L
authors.initials: DL
authors.lastname: Knol
authors.forename: Leo D
authors.initials: LD
authors.lastname: Roorda
authors.forename: Lidwine B
authors.initials: LB
authors.lastname: Mokkink
authors.forename: Raymond W J G
authors.initials: RW
authors.lastname: Ostelo
authors.forename: Erik J M
authors.initials: EJ
authors.lastname: Hendriks
authors.forename: Lex M
authors.initials: LM
authors.lastname: Bouter
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
mesh_terms: D001294:Attitude to Health; D003627:Data Interpretation, Statistical; D006801:Humans; D017116:Low Back Pain / Q000628:therapy; D017060:Patient Satisfaction; D011594:Psychometrics; D011788:Quality of Life; D012372:ROC Curve; D016896:Treatment Outcome; D035501:Uncertainty