[The authors respond:]
We thank Milorad Letic for his interest in our paper. We embarked upon this research because the concept of a plateau in detection of high-risk coronary disease is only theoretical, and no previous studies have determined whether a plateau actually exists. We chose to use regional catheterization rates from Alberta because of the availability of rich population-based data to perform this analysis. The highest regional average rates that were used in the analysis were age and sex adjusted. Formal testing does not reveal any evidence of a plateau in the detection of high-risk coronary disease, within the range of data points studied. We would strongly encourage other investigators in countries with higher cardiac catheterization rates to conduct similar work in search of a plateau at these higher rates. This may be difficult to do in many areas of the United States. Given the hybrid American health care system, there is a potential lack of population-based data such as those used in Alberta.