Overall, the level of agreement between questionnaire responses and physician claims data is moderate . In comparison with studying one year, studying two years of database contacts increased the agreement with survey results. Studying more than two years of physician contact had no effect on the level of agreement, although the sensitivity of the database to identify people with positive responses on the questionnaire was higher if longer periods of time of physician contacts were considered. However, even if five years of physician contacts were studied, the claims identified only 63.3% of people reporting an asthma attack in the 12 months before the survey, 65.1% of people reporting being on medication, 62.0% of those reporting either an attack or using medication, and 70.1% of those reporting both an attack and using medication. Sex and smoking did not significantly affect the kappa coefficient.
A similar comparison has been made between data from a survey of factors related to cardiovascular diseases and three years of physician claims from the same administrative database . The best agreement was for diabetes (k=0.72), and the second best agreement was for hypertension (k=0.59), a result similar to ours. The level of agreement we found for asthma was considerably better than for other cardiovascular conditions, including stroke and myocardial infarction.