The QI-Core R4 Encounter.diagnosis does not include an attirbute for presentOnAdmissionIndicator which would require an extension. The request originated from the Quality Data Model (QDM) version 5.5 which defines presentOnAdmissionIndicator as "The present on admission indicator (code) allows the eCQM developer to include criteria about whether each specific Encounter diagnosis was present at the time of admission (an indicator used to evaluate patient safety and adverse events)." [https://ecqi.healthit.gov/qdm].