title: The minimal clinically important difference of the Control of Allergic Rhinitis and Asthma Test (CARAT): cross-cultural validation and relation with pollen counts.
abstract: BACKGROUND
  The Control of Allergic Rhinitis and Asthma Test (CARAT) monitors control of asthma and allergic rhinitis.
  
  
  OBJECTIVE
  To determine the CARAT's minimal clinically important difference (MCID) and to evaluate the psychometric properties of the Dutch CARAT.
  
  
  METHODS
  CARAT was applied in three measurements at 1-month intervals. Patients diagnosed with asthma and/or rhinitis were approached. MCID was evaluated using Global Rating of Change (GRC) and standard error of measurement (s.e.m.). Cronbach's alpha was used to evaluate internal consistency. Spearman's correlation coefficients were calculated between CARAT, the Asthma Control Questionnaire (ACQ5) and the Visual Analog Scale (VAS) on airway symptoms to determine construct and longitudinal validity. Test-retest reliability was evaluated with intra-class correlation coefficient (ICC). Changes in pollen counts were compared with delta CARAT and ACQ5 scores.
  
  
  RESULTS
  A total of 92 patients were included. The MCID of the CARAT was 3.50 based on GRC scores; the s.e.m. was 2.83. Cronbach's alpha was 0.82. Correlation coefficients between CARAT and ACQ5 and VAS questions ranged from 0.64 to 0.76 (P < 0.01). Longitudinally, correlation coefficients between delta CARAT scores and delta ACQ5 and VAS scores ranged from 0.41 to 0.67 (P < 0.01). Test-retest reliability showed an ICC of 0.81 (P < 0.01) and 0.80 (P < 0.01). Correlations with pollen counts were higher for CARAT than for ACQ5.
  
  
  CONCLUSIONS
  This is the first investigation of the MCID of the CARAT. The CARAT uses a whole-point scale, which suggests that the MCID is 4 points. The CARAT is a valid and reliable tool that is also applicable in the Dutch population.
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Sander
authors.initials: S
authors.lastname: van der Leeuw
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Thys
authors.initials: T
authors.lastname: van der Molen
authors.affiliation: Department of Pulmonology, University Medical Center St Radboud, Nijmegen, The Netherlands.
authors.forename: P N Richard
authors.initials: PN
authors.lastname: Dekhuijzen
authors.affiliation: Department of Health Information and Decision Sciences, Faculdade de Medicina da Universidade do Porto, Porto, Portugal.
authors.forename: Joao A
authors.initials: JA
authors.lastname: Fonseca
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Frederik A
authors.initials: FA
authors.lastname: van Gemert
authors.affiliation: Department of Internal Medicine-Allergology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Roy
authors.initials: R
authors.lastname: Gerth van Wijk
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Janwillem W H
authors.initials: JW
authors.lastname: Kocks
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Helma
authors.initials: H
authors.lastname: Oosterom
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Roland A
authors.initials: RA
authors.lastname: Riemersma
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Ioanna G
authors.initials: IG
authors.lastname: Tsiligianni
authors.affiliation: Department of Pulmonology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Letty A
authors.initials: LA
authors.lastname: de Weger
authors.affiliation: 1] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] Department of Allergology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Joanne N G
authors.initials: JN
authors.lastname: Oude Elberink
authors.affiliation: 1] Department of General Practice, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands [2] GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Bertine M J
authors.initials: BM
authors.lastname: Flokstra-de Blok
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000517:prevention & control*; D003431:Cross-Cultural Comparison; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D015203:Reproducibility of Results; D065631:Rhinitis, Allergic / Q000517:prevention & control*; D011795:Surveys and Questionnaires; D055815:Young Adult