title: Reliability and validity of the Infant and Toddler Quality of Life Questionnaire (ITQOL) in a general population and respiratory disease sample.
abstract: OBJECTIVE
  To evaluate feasibility, internal consistency, test-retest reliability, and concurrent and discriminative validity of the Infant and Toddler Quality of Life Questionnaire (ITQOL) for parents of pre-school children with 12 scales (103-items) covering physical and psychosocial domains and impact of child health on parents, in comparison with the TNO-AZL Pre-school Children Quality of Life Questionnaire (TAPQOL).
  
  
  METHODS
  Parents of children from a random general population sample (2 months-4 years old; n = 500) and of an outpatient clinic sample of children with respiratory disease (5 months-[Formula: see text] years old; n = 217) were mailed ITQOL and TAPQOL questionnaires; a retest was sent after two weeks.
  
  
  RESULTS
  Feasibility: The response was >or=80% with few missing and non-unique ITQOL-answers (<2%) in both study populations. Some ITQOL-scales (3-4 scales) showed a ceiling effect (>25% at maximum score). Internal consistency: All Cronbach's alpha >0.70. Test-retest Intraclass Correlation Coefficients (ICCs) were moderate or adequate (>or=0.50; p < 0.01) for 10 ITQOL-scales.
  
  
  RESULTS
  ITQOL-scales, with a few exceptions, correlated better with predefined parallel TAPQOL scales than with non-parallel scales. Five to eight ITQOL-scales discriminated clearly between children with few and with many parent-reported chronic conditions, between children with and without doctor-diagnosed respiratory disease and with a low and a high parent-reported medical consumption (p < 0.05).
  
  
  CONCLUSIONS
  This study supported the evidence that the ITQOL is a feasible instrument with adequate psychometric properties. The study provided reference ITQOL scores for gender/age subgroups. We recommend repeated evaluations of the ITQOL in varied populations, especially among very young children, including repeated assessments of test-retest characteristics and evaluations of responsiveness to change. We recommend developing and evaluating a shortened ITQOL version.
authors.affiliation: Department of Public Health, Erasmus MC - University Medical Center Rotterdam, P.O. Box 2040, Rotterdam, ZH, 3000, CA, The Netherlands. h.raat@erasmusmc.nl
authors.forename: Hein
authors.initials: H
authors.lastname: Raat
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Landgraf
authors.forename: Rianne
authors.initials: R
authors.lastname: Oostenbrink
authors.forename: Henriëtte A
authors.initials: HA
authors.lastname: Moll
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Essink-Bot
mesh_terms: D001249:Asthma / Q000503:physiopathology / Q000523:psychology; D002669:Child Welfare / Q000523:psychology; D002675:Child, Preschool; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007223:Infant; D007229:Infant Welfare / Q000523:psychology; D008297:Male; D009426:Netherlands; D019727:Proxy; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life / Q000523:psychology*; D012140:Respiratory Tract Diseases / Q000503:physiopathology / Q000523:psychology*; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires