Tampere School of Public Health, University of Tampere, Tampere, Finland Nutrition Unit, Department of Lifestyle and Participation, National Institute for Health and Welfare, Helsinki, Finland Department of Pediatrics, Tampere University Hospital, Tampere, Finland Hospital for Children and Adolescents, Helsinki University Hospital, Helsinki, Finland Division of Nutrition, Department of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland Tampere University Hospital Research Unit, Tampere, Finland National Institute for Health and Welfare, Kuopio, Finland School of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland Social Insurance Institution, Helsinki, Finland Department of Pediatrics, University of Oulu, Oulu, Finland Department of Pediatrics, University of Turku, Turku, Finland.
Background: Valid identification of childhood asthma at the population level for epidemiological purposes remains a challenge. We aimed at validating the Finnish version of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire based on parental-reported childhood asthma. Materials and Methods: The ISAAC questionnaire has been validated against anti-asthmatic medication reimbursement data of the Finnish Social Insurance Institution, being the gold standard, among 2236 5-year-old consecutively born children (1996-2004) carrying human leukocyte antigen (HLA)-conferred susceptibility to type 1 diabetes. Two combined questionnaire questions (any wheezing symptom or use of asthma medication during the preceding 12 months plus ever asthma; any wheezing symptom or use of asthma medication during the preceding 12 months plus ever doctor-diagnosed asthma) were validated against valid reimbursement with purchase of at least one anti-asthmatic medication during a 12-month period. The validity of the questionnaire was estimated as the sensitivity, specificity, positive predictive value, negative predictive value, and Youden's index. Results: The sensitivity 0.98 [95% confidence interval (CI) = 0.92-0.99]; specificity 0.98 (95% CI = 0.97-0.98); negative predictive value 1.00 (95% CI = 1.00-1.00); and Youden's index 0.96 (95% CI = 0.96-0.96) were the same for each of the two sets of combined questions. The positive predictive value for the first combined question was 0.63 (95% CI = 0.55-0.71), while it was 0.64 (95% CI = 0.57-0.72) for the second combined question. Conclusion: The Finnish ISAAC questionnaire was highly valid and is an acceptable instrument for the survey of the prevalence of parental-reported childhood asthma for epidemiological purposes. Please cite this paper as: Nwaru BI, Lumia M, Kaila M, Luukkainen P, Tapanainen H, Erkkola M, Ahonen S, Pekkanen J, Klaukka T, Veijola R, Simell O, Knip M and Virtanen SM. Validation of the Finnish ISAAC questionnaire on asthma against anti-asthmatic medication reimbursement database in 5-year-old children. Clin Respir J 2010; DOI:10.1111/j.1752-699X.2010.00222.x.