title: The Hunter syndrome-functional outcomes for clinical understanding scale (HS-FOCUS) questionnaire: evaluation of measurement properties.
abstract: OBJECTIVE
  This study was to conduct the psychometric validation of the patient and parent versions of the Hunter syndrome-functional outcomes for clinical understanding scale (HS-FOCUS).
  
  
  METHODS
  Data collected in a 53-week placebo-controlled multinational trial were used to evaluate item performance and reliability, validity, and ability to detect change of the six HS-FOCUS function domains.
  
  
  RESULTS
  HS-FOCUS was completed by 49 patients above 12 years old and 84 parents. Floor effects and high average inter-item correlations suggested that some items were less informative or redundant. For both patients and parents, the internal consistency and test-retest reliability met the >0.70 criteria for all domains except for the breathing, sleeping, and schooling/work in patients. Construct validity showed moderate to high correlations with CHAQ, CHQ, and HUI3 in activity-related concepts. Significant differences in domain scores were found in most domains among severity in disability measured by CHAQ DIS. Significant differences in HS-FOCUS change scores were found in patients whose CHAQ DIS score also changed.
  
  
  CONCLUSIONS
  Psychometric validation of the HS-FOCUS demonstrates it is a reliable, valid, and responsive instrument that can be applied in clinical trials or disease registries. Findings on the individual item performance suggest some items could be removed without compromising its validity.
authors.affiliation: United BioSource Corporation, 26-28 Hammersmith Grove, London, W6 7HA, UK. ingela.wiklund@unitedbiosource.com
authors.forename: Ingela
authors.initials: I
authors.lastname: Wiklund
authors.forename: Mireia
authors.initials: M
authors.lastname: Raluy-Callado
authors.forename: Donald E
authors.initials: DE
authors.lastname: Stull
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Jangelind
authors.forename: David A H
authors.initials: DA
authors.lastname: Whiteman
authors.forename: Wen-Hung
authors.initials: WH
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D016532:Mucopolysaccharidosis II / Q000523:psychology*; D063868:Patient Outcome Assessment; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012890:Sleep; D011795:Surveys and Questionnaires / Q000592:standards*; D055815:Young Adult