Population-based prevalence estimates can be calculated once cases of a chronic disease have been ascertained in administrative data. The number of cases identified according to a given case definition becomes the numerator, while the population for the year in question becomes the numerator.

For the MCHP report, the following time periods were used to define cross-sectional chronic disease prevalence estimates for Manitoba, Canada:

1 year case definition: April 1, 2002 to March 31, 2003

2 year case definition: April 1, 2001 to March 31, 2003

3 year case definition: April 1, 2000 to March 31, 2003