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. 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 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). In the scenario described in the inquiry in which a STEMI developed five days into the subsequent inpatient encounter after the patient’s ED encounter had ended, the patient should not be captured in the measure denominator. The measure’s initial population includes all emergency department (ED) encounters for patients 18 years and older at the start of the encounter with a diagnosis of STEMI during the ED encounter that ends during the measurement period (aside from those meeting measure denominator exclusions or exceptions). As such, the measure does not capture a STEMI that presents outside of an ED encounter, such as a subsequent inpatient encounter, as this is not the measure’s intent. 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.   Additionally, we recommend ensuring that ED encounters and subsequent inpatient encounters are documented in the EHR as two separate encounters, instead of being combined. If it is the case that these encounters were being combined in EHR documentation, we recommend working with your EHR vendor to document the ED encounter and the inpatient encounter separately, and map the ED encounter to the “Encounter, Performed”: “Emergency Department Evaluation and Management Visit” QDM datatype, and the inpatient encounter to the “Encounter, Performed”: “Encounter Inpatient” QDM datatype. Documentation of both of these encounters separately will help ensure that diagnoses occurring during the inpatient encounter are not erroneously pulled into the ED encounter.