Agreement between asthma questionnaire and health care register data.

PURPOSE

Risk factors and consequences of asthma can be studied by using validated questionnaires. The overall objective of this study was to assess the agreement of parental-reported asthma-related questions regarding their children against Swedish health care registers.

METHODS

We linked a population-based twin cohort of 27 055 children aged 9 to 12 years to the Swedish Prescribed Drug Register, National Patient Register, and the primary care register. Parent-reported asthma was obtained from questionnaires, and diagnoses and medication were retrieved from the registers. For the agreement between the questionnaire and the registers, Cohen's kappa was estimated.

RESULTS

The kappa of the "reported ever asthma" against a "register-based ever asthma" was 0.69 and 0.57 between the parental-"reported doctor's diagnosis" and "register-based doctor's diagnosis." The highest agreement between "reported current asthma" and "register-based current asthma" with at least 1 dispensed medication or a diagnosis applied to different time windows was seen for an 18-month window (kappa = 0.70).

CONCLUSIONS

We found that parent-reported asthma-related questions showed on average good agreement with the Swedish health care registers. This implies that in-depth questionnaires with rich information on phenotypes are suitable proxies for asthma in general and can be used for health care research purposes.