The intent of excluding ED/observation visits that result in an inpatient stay is to not double count events. For example, an ED visit with a principal mental health diagnosis that resulted in an inpatient stay for a principal diagnosis of mental health is reported only once in the “Inpatient Stay” category. An ED visit with a principal mental health diagnosis that resulted in an inpatient stay with a principal diagnosis for something other than mental health (e.g., heart attack) is reported only once in the “ED” category.
HEDIS 2019