If multiple diagnosis codes are used, which statement about their ordering is true?

• A. Principal diagnosis is always listed first among the diagnosis codes.
• B. The most recent diagnosis is listed first.
• C. Diagnoses are listed in alphabetical order.
• D. The principal diagnosis is optional.

Answer: (A)

On a UB-04 inpatient claim, the first diagnosis listed is the principal diagnosis—the condition chiefly responsible for the patient’s admission or encounter. This placement communicates the main reason for care and guides how the rest of the diagnoses are interpreted in relation to that primary issue. The remaining diagnoses are added after the principal one in an order that reflects their relevance to the encounter and the care provided, not the order in which they were diagnosed or alphabetical order. Therefore, the rule that the principal diagnosis is always listed first among the diagnosis codes is the correct approach. The other options don’t fit because the primary ordering isn’t based on recency or alphabetical order, and the principal diagnosis is not optional for inpatient claims.