Which code is listed first when sequencing a diagnosis?

The primary diagnosis responsible for services provided is listed first when sequencing a diagnosis because it is the main reason for a patient's encounter with the healthcare provider. This diagnosis directly influences the course of treatment and the services rendered. Proper coding guidelines dictate that the primary diagnosis should be reported before any other conditions to reflect accurately the focus of the patient's visit and the basis of medical necessity for the services provided.

In medical coding, this sequence is crucial as it ensures that billing and reimbursement processes align correctly with the reasons for patient care. Primary diagnoses typically represent the most significant factor impacting patient management and are essential for quality reporting and care outcomes.

Other options, although important in their own right, follow the primary diagnosis in a coding list. Coexisting conditions, history codes, and conditions treated in the past serve as additional context or support for the primary diagnosis but do not take precedence in the sequencing process.