Thank you for your inquiry regarding CMS996v5, Appropriate Treatment for ST-Segment Elevation Myocardial Infarction (STEMI) Patients in the Emergency Department (ED). The QDM does not prescribe the source of diagnosis data in the EHR. STEMI diagnoses may be found in a patient’s problem list, encounter diagnosis list, claims data, or other sources within the EHR. A patient with a STEMI diagnosis may be captured in the measure in two ways, as indicated by the measure logic definition below found in the measure’s HTML file posted on the eCQI Resource Center [ https://ecqi.healthit.gov/sites/default/files/ecqm/measures/CMS996v5.html ]. ED Encounter with STEMI Diagnosis "ED Encounter with Encounter Diagnosis of STEMI"   union "ED Encounter with Diagnosis of STEMI" First, a STEMI diagnosis can be pulled directly from the ED encounter if a STEMI diagnosis was coded during the encounter. Second, the patient can have a diagnosis pulled from a claim, problem list, or other source in the EHR as long as the prevalencePeriod of the STEMI diagnosis started during the ED encounter relevantPeriod. PrevalencePeriod is an attribute of the “Diagnosis” datatype and signifies the onset dateTime to abatement dateTime of the STEMI diagnosis. RelevantPeriod is an attribute of the “Encounter, Performed”: “Emergency Department Evaluation and Management Visit” and signifies the startTime that the encounter began (admission time) to the stopTime that the encounter ended (discharge time). To differentiate between active and historic STEMI diagnoses in the problem list, it’s important for both the onset and abatement times to be populated in the EHR and mapped to the appropriate QDM data elements to avoid misattribution.