The circumstances of an inpatient’s admission always govern the selection of the principal diagnosis, as defined in the Uniform Hospital Discharge Data Set (UHDDS). The UHDDS defines the principal diagnosis as “the condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.”
This definition has been expanded to include all non-outpatient settings such as acute care, short-term, long-term care, and psychiatric hospitals; home health agencies; rehab facilities; nursing homes, etc. In addition, the UHDDS definitions apply to hospice services (all levels of care). When determining principal diagnosis, coding conventions in the ICD-10-CM, the Tabular List, and Alphabetic Index should be followed. It is essential for medical record documentation to be complete and consistent for the application of all coding guidelines to be successful.
The significance of consistent and comprehensive documentation in the medical record is essential and cannot be stressed enough. Without such documentation, it would be incredibly challenging, if not impossible, to apply all coding protocols.
https://www.cms.gov/files/document/fy-2023-icd-10-cm-coding-guidelines-updated-01/11/2023.pdf
Code for symptoms, signs, and ill-defined conditions
Codes from Chapter 18 (Symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified) should not be used as the principal diagnosis when a more specific and definitive diagnosis has been identified.
Two or more interrelated conditions, each potentially meeting the definition for principal diagnosis
When two or more interrelated conditions are present (such as diseases found in the same ICD-10-CM chapter or conditions that typically appear with a certain disease), either can be listed as the principal diagnosis, unless the reason for admission, treatment is given, Tabular List or Alphabetic Index suggest otherwise.
Two or more diagnoses that equally meet the definition for principal diagnosis
If two or more diagnoses are equally applicable as the principal diagnosis based on the circumstances of admission, diagnostic workup, and/or therapy provided, and none of the Alphabetic Index, Tabular List, or other coding guidelines provide direction on sequencing, any of the diagnoses can be sequenced first.
Two or more comparative or contrasting conditions
In cases where two or more contrasting or comparative diagnoses are documented using terms such as “either/or”, they should be coded as if both diagnoses were confirmed. The diagnoses should then be sequenced based on the circumstances of the admission. If it is not possible to determine which diagnosis should take priority, either one can be sequenced first.
The original treatment plan was not carried out
For the principal diagnosis, sequence the condition that prompted the admission to the hospital, even if treatment could not be administered due to unforeseen circumstances.
Complications of surgery and other medical care
When a patient is admitted for treatment of a complication resulting from surgery or other medical care, the complication should be sequenced as the principal diagnosis and classified to the T80-T88 series. If the code does not provide enough information to accurately describe the complication, an additional code for the specific complication should be assigned as the principal diagnosis.
Uncertain Diagnosis
If the diagnosis documented at the time of discharge is qualified with terms like “probable,” “suspected,” “likely,” “questionable,” “possible,” “still to be ruled out,” “compatible with,” “consistent with,” or any other terms indicating uncertainty, then it should be coded as if the condition was established. The basis for such guidelines is the diagnostic workup, arrangements for further workup or observation, and initial therapeutic approach that correspond most closely with the diagnosed condition.