Thus, the estimates of prevalence derived from the survey and the administrative data include two overlapping groups of people. In each, the diagnosis of asthma seems justifiable, but the agreement between the survey and the data is only moderate to substantial. To put this in perspective, a number of clinical conditions show measures of diagnostic agreement (kappas) between two physicians of about 0.6 . Moreover, the ‘physician’-diagnosed asthma prevalence underestimates prevalence estimates based on reported asthma symptoms (Table 3). On the other hand, both estimates of prevalence are useful, although for different purposes. Health care utilization estimates obtained from administrative databases are particularly useful for studying trends over time , an objective very difficult to achieve with survey methodology. The need for information on the prevalence of common conditions has never been greater, as Regional Health Authorities in Canada, and probably elsewhere, assume planning and budgetary responsibilities for health care.
Because the study population was restricted to the ages of 20 to 44 years, conclusions may not be generalizable to those younger or older. The diagnosis of asthma may be more difficult and controversial in other age groups. Because of this, there may be, although not necessarily, less agreement between records in administrative databases and self-reports by surveyed subjects in these age groups.