Thank you for your inquiry regarding CMS996v5, Appropriate Treatment for ST-Segment Elevation Myocardial Infarction (STEMI) Patients in the Emergency Department (ED). The dementia exclusion is defined by the following definition 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 ].   Active Exclusion Diagnosis At Start Of ED Encounter   "ED Encounter With STEMI Diagnosis" EDwSTEMI     with ( ["Diagnosis": "Active Bleeding or Bleeding Diathesis, Excluding Menses"]       union ["Diagnosis": "Malignant Intracranial Neoplasm Group"]       union ["Diagnosis": "Cerebral Vascular Lesion"]       union ["Diagnosis": "Dementia and Related Intracranial Pathologies"]       union ["Diagnosis": "Pregnant State"]       union ["Diagnosis": "Allergy to thrombolytics"] ) ActiveExclusionDx       such that ActiveExclusionDx.prevalencePeriod overlaps before EDwSTEMI.relevantPeriod The QDM does not prescribe the source of diagnosis data in the EHR. Dementia diagnoses may be found in a patient’s problem list, encounter diagnosis list, claims data, or other sources within the EHR. We recommend working with your EHR vendor to map dementia diagnoses documented in the EHR to the QDM Diagnosis datatype. The exclusion definition above shows that the dementia 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, the patient’s dementia diagnosis needs to start before the ED encounter begins for the encounter to be excluded from the measure denominator. Since the time stamp in the inquiry records the dementia diagnosis at 10:42, which is after the start of the ED encounter relevantPeriod (10:26), this particular case does not meet the denominator exclusion.