Parental questionnaires provided reliable data on childhood asthma compared with national registers.

ABSTRACT

BACKGROUND: Much of our knowledge of childhood asthma comes from questionnaire-based studies. Our main aim was to assess the agreement between parental-reported data at 12 years of age and data from two national Swedish registers. METHODS: Data were obtained from the prospective, longitudinal, population-based Children of Western Sweden cohort, which focused on children born in 2003. The parents answered questionnaires at six months and one, four, eight and 12 years of age. Personal identity numbers linked 3634 children to the Swedish Prescribed Drug Register (SPDR) and the National Patient Register (NPR). RESULTS: At 12 years of age, there was substantial overall agreement between the asthma medication reported by the parents in the questionnaire and the SPDR for any asthma medication (94.8%, kappa 0.71) and maintenance treatment (95.3%, kappa 0.68). In contrast, the agreement between the outpatient asthma diagnoses in the NPR and the questionnaire-based asthma was 30.5% and it was 32.8% between the NPR and the dispensed asthma medication in the SPDR. Hospitalization was rare for obstructive diseases after early childhood, and 38.2% of the 12-year-old children only received a short-acting beta agonist, with no maintenance treatment. CONCLUSION: There was good agreement between the questionnaire-based data on asthma medication and the national drug register, but the National Patient Register provided incomplete information on asthma diagnoses, probably because it did not include primary care diagnoses. The results show that well-constructed parental questionnaires can provide reliable data on childhood asthma.