Low agreement between Swedish national registers and parental questionnaires on allergic rhinitis

Background Allergic rhinitis (AR) has been well documented using questionnaire‐based studies. Here, we examine the agreement between parental‐reported data during childhood with the emphasis on 12‐year‐olds and data from two national Swedish registers to determine whether register data on AR can supplement or replace questionnaire data. Methods Data were collected from a prospective, longitudinal cohort study of children born in western Sweden in 2003. Parental questionnaires were filled out at 6 months and one, four, eight, and 12 years of age. A total of 3634 children were linked to the Swedish Prescribed Drug Register (SPDR) and the National Patient Register (NPR) using personal identity numbers. The agreement between the register and questionnaire data was estimated using Cohen's kappa with 95% confidence intervals. Results According to the SPDR, 9.9% (n = 360/3634) of the children were dispensed specific AR medication at 11–13 years of age compared with the 12 years questionnaire where 23% reported AR medication use during the last 12 months. The overall agreement between questionnaire and SPDR data on AR medication was slight (kappa 0.05). At 11–12 years, 1.8% (n = 65/3634) of the children received an outpatient AR diagnosis in the NPR, while 10% reported doctor‐diagnosed AR in the questionnaire. The overall agreement between questionnaire and NPR data on AR diagnosis was slight (kappa 0.16). Conclusions There was poor agreement between questionnaire and register data regarding AR and dispensed medication. Explanations could include over‐the‐counter drugs and diagnosis in primary care, which are not included in the registers.