The intent is to be able to represent principal diagnosis as being the coded diagnosis/problem in the encounter, chiefly responsible for the admission of the patient to the hospital for care while also allowing for the identification of a patient’s disease, illness, injury, or condition through the diagnosis attribute in “Encounter, Performed”. From a clinical perspective (as opposed to billing), it is likely that the principal diagnosis in an ED visit is different than the principal diagnosis in an Inpatient encounter. They can or may occur at different times and be unrelated. Where it may be problematic is when an episode turns into multiple encounters - when an ED visit turns Inpatient. In such cases, the principal diagnosis needs to be derived only from the Inpatient encounter, if in fact that is what you are suggesting when an outbound QRDA file is submitted.