The rising prevalence of asthma: true increase, diagnostic exchange or diagnostic accuracy?

In the midst of frequent reports about "the asthma epidemic," results from a number of studies by the manitoba centre for health policy have shown stable or decreasing prevalence of an overall indicator of respiratory diseases which includes asthma. To resolve these apparently contrary findings, we conducted a time trend analysis using administrative data. results revealed significant potential for diagnostic exchange: asthma prevalence increased, but that of bronchitis decreased.