title: What is a clinically relevant change on the HIT-6 questionnaire? An estimation in a primary-care population of migraine patients.
abstract: OBJECTIVE
  To interpret questionnaire scores, clinicians and researchers need to know what change in score reflects a meaningful change in the condition of an individual patient, and what difference reflects a meaningful difference between groups. These values differ between different populations. We determined the within-person minimally important change (MIC) and the between-group minimally important difference (MID) of the Headache Impact Test-6 (HIT-6) questionnaire in a primary-care population of migraine patients.
  
  
  METHODS
  We included 490 patients who participated in a clinical trial on the treatment of migraine in primary care. We compared their change scores on the HIT-6 questionnaire between baseline and at three-months follow-up with the answers to two anchor questions according to the 'mean change approach' and the 'ROC curve approach'.
  
  
  RESULTS
  The within-person MIC was estimated to be between -2.5 points (mean change approach) and -6 points (ROC curve approach). The choice for the within-person MIC value depends on the consequences of false positives and false negatives in a particular setting. The between-group MID was estimated at -1.5 points.
  
  
  CONCLUSIONS
  We determined the within-person MIC and between-group MID for the HIT-6 in a primary-care population of migraine patients. We recommend the use of these values for clinical care and for research.
authors.affiliation: Leiden University Medical Center, the Netherlands.
authors.forename: Antonia F H
authors.initials: AF
authors.lastname: Smelt
authors.forename: Willem J J
authors.initials: WJ
authors.lastname: Assendelft
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
authors.forename: Michel D
authors.initials: MD
authors.lastname: Ferrari
authors.forename: Jeanet W
authors.initials: JW
authors.lastname: Blom
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000175:diagnosis* / Q000523:psychology*; D009426:Netherlands; D010147:Pain Measurement / Q000379:methods* / Q000523:psychology; D011320:Primary Health Care; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Headache Impact Test (HIT-6); Migraine; minimally important change; minimally important difference; outcome research