Ratio measures in HQMF used pointers to refer to a Denominator’s or Numerator’s associated Initial Population. In addition, a Measure Observation could be associated to a Denominator or Numerator through a similar mechanism. Although the Quality measure IG mentions that Ratio's would act similar for FHIR (refer to http://hl7.org/fhir/us/cqfmeasures/STU2/measure-conformance.html#ratio-measures), no mention is mentioned in the specific Ratio profile to the MeasureObservation splice (for reference, refer to the Continuous Variable measure profile) or the related cqfm-criteriaReference for Numerator or Denominator, in the case where each of those populations would need to reference a separate Initial Population in the same measure group.