title: Development and initial testing of Asthma Predictive Index for a retrospective study: an exploratory study.
abstract: OBJECTIVE
  Asthma Predictive Index (API) has been used for predicting asthma in prospective or cross-sectional studies, not for a retrospective study. We aim to develop and validate API for a retrospective study.
  
  
  METHODS
  This is a cross-sectional study based on a convenience sample of children who participated in a previous retrospective cohort study. API was operationalized by two or more wheezing episodes in a year during the first 3 years of life PLUS one of the major or two of the minor criteria of the original API. We assessed validity of retrospective API against Predetermined Asthma Criteria (PAC) which has been extensively used in clinical studies for asthma. We assessed criterion validity by measuring kappa and agreement rate between API and PAC and construct validity by determining associations of API with known risk factors for asthma.
  
  
  RESULTS
  Of the eligible 105 children, 55 (52.4%) were male, 90 (85.7%) Caucasians, and the mean age (±SD) was 5.8 years (±1.5). API criteria was met by 15 (14.3%), compared to 33 (31.4%) by PAC, respectively. The agreement rate and kappa between API and definite asthma of PAC were 89.5% and 0.66 (p < 0.01). Atopic conditions, lower parental education, no history of breastfeeding and family history of asthma were significantly associated with risk of asthma by API.
  
  
  CONCLUSIONS
  Application of API to a retrospective study for ascertaining asthma status is suitable. Our study findings need to be replicated by future studies with a larger sample size.
authors.affiliation: Department of Pediatric and Adolescent Medicine .
authors.forename: Chung-Il
authors.initials: CI
authors.lastname: Wi
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Park
authors.forename: Young J
authors.initials: YJ
authors.lastname: Juhn
mesh_terms: D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D001942:Breast Feeding; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004802:Eosinophilia / Q000175:diagnosis; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015203:Reproducibility of Results; D012107:Research Design; D012135:Respiratory Sounds / Q000175:diagnosis; D012189:Retrospective Studies; D012307:Risk Factors; D057566:Self Report; D012737:Sex Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014028:Tobacco Smoke Pollution
chemical_list: D014028:Tobacco Smoke Pollution
keywords: Asthma ascertainment; Predetermined asthma criteria; asthma predictive index; retrospective study; wheezing