Thank you for your inquiry regarding CMS996: Appropriate Treatment for ST-Segment Elevation Myocardial Infarction (STEMI) Patients in the Emergency Department (ED). We understand the intent of your inquiry is to ensure that historic STEMI diagnoses are not captured in the measure. For context, we emphasize that the QDM does not prescribe the source of diagnosis data in the EHR. 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/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" ))   First, a STEMI diagnosis can be pulled directly from the ED encounter if a STEMI diagnosis was coded at any point 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” datatype 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 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. To ensure that historic STEMI diagnoses are not pulled into the measure, we recommend not coding the STEMI diagnosis in the encounter diagnosis field on the EHR which maps to the “Encounter, Performed” datatype diagnosis attribute (method 1 mentioned above). Instead, we recommend accurately documenting that the STEMI diagnosis onset dateTime occurred before the ED encounter in the patient’s problem list, which maps to the “Diagnosis” datatype (method 2 described above).