When two diagnoses equally meet the definition of principal diagnosis, either condition may be sequenced first when the circumstances of admission, diagnostic workup, and treatment equally support both and no specific coding guideline, tabular instruction, or other sequencing rule directs otherwise.
The principal diagnosis cannot be selected based on which option generates higher payment. Financial outcome is not a legitimate sequencing criterion.
Likewise, chronological age of the diagnosis does not determine principal-diagnosis status. The principal diagnosis is established after study as the condition chiefly responsible for occasioning the admission.
A CDI query may be appropriate when the documentation does not actually establish whether both diagnoses equally occasioned the admission. However, querying simply because one sequencing choice would produce a more favorable MS-DRG is inappropriate.
This scenario tests the distinction between valid coding flexibility and improper reimbursement-driven documentation practices. CDI professionals must understand coding conventions well enough to avoid unnecessary queries while recognizing genuine ambiguity that requires provider clarification.
The FY 2026 MS-DRG grouper and Definitions Manual published by CMS provide the applicable grouper logic for the current fiscal year.
CCDS Reference Topics: Principal diagnosis; equally qualifying diagnoses; sequencing; ethical reimbursement practice.
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