Diagnosis Coding for Principal Diagnosis

Diagnosis coding is a pivotal component of hospital billing. Selecting the correct principal and secondary diagnosis codes facilitates timely and accurate claims processing.

The attending physician is responsible for listing the patient’s principal and secondary diagnoses on the “attestation” or “discharge face sheet” when a patient is discharged from the hospital.

Selecting the principal diagnosis is the most important factor in the assignment of the diagnosis-related group (DRG) number. This assignment ultimately affects the amount of payment received by the hospital.

The principal diagnosis, as defined in the NUBC Official UB-04 Data Specifications Manual, is "the condition established after study to be chiefly responsible for occasioning the admission of the patient for care."

Note: There are instances when the principal diagnosis and the admitting diagnosis are not the same. For example, a patient admitted with chest pain may be subsequently diagnosed with an anterior wall myocardial infarction (MI). In this case, the principal diagnosis would be MI, while the admitting diagnosis would be chest pain. The principal diagnosis code should be for services rendered, not for the member's historical diagnosis.

For a diagnosis to be considered valid, the documentation in the medical record must be complete, thorough, consistent, and supportive of the diagnosis listed on the claim. This requires a joint effort of the attending physician and the facility's medical records staff.

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