Which of the following is a guideline for selecting a principal diagnosis in non-outpatient settings?

In non-outpatient settings, the correct guideline for selecting a principal diagnosis is covered in ICD-10-CM Guidelines section II. This section provides essential instructions on how to determine the principal diagnosis based on the patient's condition upon admission. It specifically focuses on inpatient care situations, emphasizing that the principal diagnosis is the condition that, after study, is determined to be the primary reason for the patient’s hospitalization. This guidance ensures that healthcare providers consistently identify the most significant diagnosis which justifies the necessity for medical services and supports appropriate coding for reimbursement purposes.

In contrast, the other options refer to guidelines that address different aspects or settings in healthcare coding. For instance, section I primarily outlines general guidelines applicable across all types of settings, while sections III and IV focus on specific scenarios like coding for outpatient services or complications or comorbidities in a hospital context. Therefore, when dealing with non-outpatient settings, section II is the definitive guideline that should be referenced for accurate principal diagnosis selection.