Restrict stratification of ratio measure - QM #142

Existing Wording: A constraint was added for Stratification around a stratification's expression type for event-based eCQMs:

For event-based measures (e.g. episode-of-care), the CQL expression SHALL return a list of events of the same type as the population criteria.

Proposed Wording: Recommend restricting stratification to eCQMs that are not based on a Ratio.

Comment:

It is not clear from the specification about how this constraint would be applied to a Ratio measure that has different types in the same population criteria section. Since there are no examples of Ratio mesures in the posted CMS eCQMs and it is not clear how stratification really applies in a Ratio measure, based on conversations with ESAC, we recommend adding a constraint that Stratification cannot be used in a Ratio measure.

Summary:

Restrict stratification of ratio measure