A primary diagnosis describes the underlying cause of a patient's admission to the hospital. It is assigned after the completion of diagnostic tests and examinations. The difference from a research standpoint is that billing diagnoses can be more homogenous, since billing coders are able to use a specific set of rules to assign the billing code. While these two options may be the same, this is not always the case, as billing rules may require the coder to assign a different billing diagnosis than the assigned physician as the diagnosis of the encounter.
Knowing how to differentiate admission, primary, primary, and secondary diagnoses for reporting and sequencing purposes can be intimidating and confusing. Despite the slight differences between the primary and primary diagnoses, many health professionals use the term interchangeably. In some patients, this may be the same as the main diagnosis, but in others it will be different.
