Comparison of parent reported physician diagnosed asthma and general practitioner registration.

OBJECTIVE: To compare parent reported physician diagnosed asthma from questionnaires for epidemiological purposes, to general practitioner (GP) recorded childhood asthma. METHODS: This study was embedded in the KOALA Birth Cohort Study with regular follow-up by ISAAC core questions on asthma in 2834 children in two different recruitment groups, with 'conventional' lifestyles or 'alternative' lifestyles. At age 11-13 years these data were linked to data extracted from GP records. We compared parent reported physician diagnosed asthma, asthma medication use, and current asthma with GP recorded asthma diagnosis and medication. Two different combinations of questions were used to define current asthma (i.e. ISAAC and MeDALL based definition). RESULTS: Among 958 children with information provided both by the parents and GPs, 98 children (10.2%) had parent reported physician diagnosed asthma, 115 children (12.0%) had a GP recorded asthma diagnosis (Cohen's kappa 0.49; 95% CI 0.40 to 0.57). Discrepant cases showed that asthma symptoms at an early age led to different labeling between parents and GP. The agreement between ISAAC based definition and MeDALL based definition was excellent (Cohen's kappa 0.82; 95% CI 0.74 to 0.88). CONCLUSION: Parent reported physician diagnosed asthma and GP recorded childhood asthma had only moderate agreement, and is possibly influenced by labeling early transient wheeze as asthma diagnosis. It is important that parent reported physician diagnosed asthma is combined with additional questions such as current asthma symptoms and asthma medication use, as used in ISAAC or MeDALL based current asthma, in order to obtain reliable information for epidemiological research.