Thank you for your inquiry specific to CMS871v3 Hospital Harm – Severe Hyperglycemia. Although the intent of the denominator exclusion has not changed from the previous version, the logic was revised to ensure the glucose tests are constrained to only the qualifying encounter, and to decrease data processing performance issues by restricting evaluation to only the pertinent glucose test data elements. Looking at the "Initial Glucose Greater Than or Equal to 1000 within 1 Hour Prior To and 6 Hours After Encounter Start” definition, we see it references two other define statements in bold: define “Initial Glucose Greater Than or Equal to 1000 within 1 Hour Prior To and 6 Hours After Encounter Start” "Glucose Greater Than or Equal to 1000 within 1 Hour Prior To and 6 Hours After Encounter Start" GlucoseResult1000   where not ( GlucoseResult1000.id in "Glucose Tests Earlier Than Glucose Greater Than or Equal to 1000 within 1 Hour Prior To and 6 Hours After Encounter Start".id ) The first one, "Glucose Greater Than or Equal to 1000 within 1 Hour Prior To and 6 Hours After Encounter Start”, looks for a glucose with a result >=1000 during a 7-hour interval (between 1 hour prior to and 6 hours after the encounter start). The second one, “Glucose Tests Earlier Than Glucose Greater Than or Equal to 1000 within 1 Hour Prior To and 6 Hours After Encounter Start”, evaluates to see if there were any glucose tests with a result >=1000 earlier than the start of the 7-hour window. The ‘where not’ used here is to capture an initial glucose >=1000 within the 7-hour window where there is NOT a glucose test earlier that has a result >=1000. This ensures that only the initial glucose w/result within the 7-hour window, and not before, is evaluated. We appreciate the feedback included in your inquiry. We will consider providing clarifying information in the measure specification during the upcoming eCQM Annual Update cycle.