Thank you for your inquiry regarding CMS996: 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 however, we would advise to use standardized or structured data that is the most clinically accurate. For additional information, we note that the measure logic definition can be found in the measure’s HTML file posted on the eCQI Resource Center [ https://ecqi.healthit.gov/sites/default/files/ecqm/measures/CMS996-v6.3.000-QDM.html ]: ED Encounter with STEMI Diagnosis "ED Encounter During MP" EDEncounterinMP     where (exists (["Diagnosis": "STEMI"] DxSTEMI       where DxSTEMI.prevalencePeriod starts during EDEncounterinMP.relevantPeriod))     or (exists( EDEncounterinMP.diagnoses EncounterDiagnosis       where EncounterDiagnosis.code in "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. 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” datatype and signifies the startTime that the encounter began (admission time) to the stopTime that the encounter ended (discharge time). For both methods, the source is not prescriptive as described earlier. To differentiate between active and historic diagnoses in the problem list, it is 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.