Thank you for your inquiry regarding CMS996: Appropriate Treatment for ST-Segment Elevation Myocardial Infarction (STEMI) Patients in the Emergency Department (ED). Several of the measure’s denominator exclusion criteria exclude diagnoses that were present on admission as indicated in the timing components of the measure logic. For example, the measure’s ‘Active Exclusion Diagnosis at Start of ED Encounter’ measure exclusion definition found in the human readable file ( https://ecqi.healthit.gov/sites/default/files/ecqm/measures/CMS996-v6.3.000-QDM.html ) shows that the diagnosis prevalencePeriod (or time from diagnosis onset to abatement) “overlaps before” the ED encounter relevantPeriod (or the time the encounter began to the time the encounter ended). Meaning, that diagnoses captured by this exclusion can start before or during the ED encounter for the encounter to be excluded from the measure denominator. Although the presentOnAdmissionIndicator attribute is not used for this exclusion, the “overlaps before” measure logic should exclude conditions that were present on admission as long as the “Encounter, Performed”: “Emergency Department Evaluation and Management Visit” relevantPeriod is accurately coded. The measure currently does not use the presentonadmissionIndicator attribute in its denominator exclusions. The measure developer team may consider using a presentOnAdmissionIndicator attribute for the “Encounter, Performed” datatype in a future Annual Update.