Selection of Principal Diagnosis

The circumstances of inpatient admission always govern the selection of principal diagnosis.

The principal diagnosis is defined in the Uniform Hospital Discharge Data Set (UHDDS) as “that condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.” The UHDDS definitions are used by hospitals to report inpatient data elements in a standardized manner.

These data elements and their definitions can be found in the July 31, 1985, Federal Register (Vol. 50, No, 147), pp. 31038-40. Since that time, the application of the UHDDS definitions has been expanded to include all non-outpatient settings (acute care, short term, long term care and psychiatric hospitals; home health agencies; rehab facilities; nursing homes, etc.).

The UHDDS definitions also apply to hospice services (all levels of care). In determining principal diagnosis, coding conventions in the ICD-10-CM, the Tabular List and Alphabetic Index take precedence over these official coding guidelines. (See Section I.A., Conventions for the ICD-10-CM) The importance of consistent, complete documentation in the medical record cannot be overemphasized.

Without such documentation the application of all coding guidelines is a difficult, if not impossible, task.