Why Sequencing Matters
Proper sequencing of diagnosis codes affects reimbursement, quality reporting, and the clinical accuracy of the coded record. The Uniform Hospital Discharge Data Set 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.
Selecting the Principal Diagnosis
Selecting the principal diagnosis requires the coder to review the entire episode of care and determine which condition, after diagnostic workup and treatment, was truly responsible for the admission, which may differ from the admitting diagnosis documented at the time of arrival. When two or more diagnoses equally meet the definition of principal diagnosis, coding guidelines provide direction on which to sequence first, often based on which diagnosis is listed first by the provider when either could be considered principal.
Additional Diagnoses
Additional, or secondary, diagnoses are conditions that coexist at the time of admission, develop subsequently, or affect patient care during the encounter through requiring clinical evaluation, therapeutic treatment, diagnostic procedures, extended length of stay, or increased nursing care and monitoring. Conditions that do not meet these criteria generally should not be coded, even if documented in the history.
Coding Conventions
ICD-10-CM conventions such as "code first," "use additional code," and "code also" notes direct proper sequencing for certain conditions, particularly manifestation and etiology relationships where the underlying condition must be sequenced before the manifestation it causes. Excludes1 and Excludes2 notes further guide which codes cannot or should not be reported together.
Chapter-Specific Guidelines
Certain ICD-10-CM chapters include specific sequencing instructions, such as obstetric chapter guidelines requiring an obstetric code be sequenced first for pregnancy-related encounters, or guidelines for sequencing certain infectious disease codes.
Complications
When coding complications of care, coders must determine whether a documented relationship exists between the complication and a procedure or device, applying combination codes when available and ensuring the complication code accurately reflects the cause-and-effect relationship supported by physician documentation.