3rd Pediatric Allergy and Asthma Meeting (PAAM).

Background: Valid measures of asthma and eczema in epidemiological studies may be a challenge. Population-based registers can be useful as they do not rely on recall and allow for follow-up. Our aim was to ascertain if asthma/eczema medication is a suitable proxy for asthma/ eczema and to validate register-based asthma diagnoses. Method: Data were retrieved on all 0-17-year-old individuals with reported asthma/eczema medication in the Swedish Prescribed Drug Register (SPDR) and/or an asthma diagnosis in the National Patient Register (NPR) between 2005-2009 (N=121,944). Medical records retrieved from prescribing units, for 2,250 randomly selected individuals, were reviewed to estimate the proportion of individuals with 1) asthma/ eczema medication in the SPDR who had a doctor diagnosis of asthma/ eczema and/or; 2) fulfilled predefined criteria of asthma by the Swedish Paediatric Society (positive predictive value, PPV); 3) an asthma diagnosis in the NPR verified as asthmatics by predefined criteria. Results: PPV for asthma medication as a proxy for a doctor diagnosis of asthma was 0.68 (95%CI: 0.64-0.72) in pre-school children (0-4.5 years) and 0.89 (95%CI: 0.85-0.92) in school-age children (>4.5-17 years). The corresponding PPV for predefined criteria of asthma was 0.75 (95%CI: 0.70-0.78) and 0.94 (95%CI: 0.910.96) in pre-school children and schoolage children respectively. Almost all (99%) of school-age children and 78% of pre-school children with an asthma diagnosis in the NPR were verified as asthmatics. PPV for eczema medication as a proxy for an eczema diagnosis was estimated to 0.45 (95% CI: 0.38-0.51) in children 0-17 years. Conclusion: Asthma medication is the SPDR is a suitable proxy for asthma in older children; the same approach is insufficient for eczema. Furthermore, the quality of asthma diagnoses in the NPR is high. This validation study of two Swedish registers opens for future large nationwide studies on asthma.