Figure 2-1. Three-phase process for determining patient severity of illness subclass (Text Description)

Flowchart of the three-phase process of determining the severity of illness subclass. The process begins with the step to Assign APR DRG (All Patient Refined Diagnosis Related Group).

Phase 1 is "Determine the severity level of each secondary diagnosis," and includes the following steps:

• Eliminate secondary diagnoses that are associated with the principal diagnosis.
• Assign each secondary diagnosis its standard severity of illness level.
• Modify the standard severity of illness level of each secondary diagnosis based on:
  • Age
  • APR DRG and PDX
  • APR DRG

Phase 2 is "Determine the base severity of illness subclass of the patient," and includes the following steps:

• Eliminate secondary diagnoses that are associated with other secondary diagnoses.
• Set the base severity of illness subclass of the patient to the highest severity of illness level of any of the secondary diagnoses.
• Reduce the subclass of patients with a base subclass of major or extreme to the next lower subclass unless the patient has multiple high severity of illness secondary diagnoses.

Phase 3 is "Determine the final severity of illness subclass of the patient," and includes the following steps:

• Modify patient severity of illness subclass based on the presence of specific combinations of:
  • APR DRG and principal diagnosis.
  • APR DRG and age, or APR DRG and principal diagnosis and age.
  • APR DRG and non-OR [operating room] procedure.
  • APR DRG and OR procedure.
  • APR DRG for ECMO and presence or absence of certain OR procedures.
  • APR DRG and pairs of OR procedures.
  • APR DRG and principal diagnosis and non-O R procedure.
• Compute the final patient severity of illness subclass based on the Phase 3 base patient severity of illness subclass and the Phase 3 severity of illness subclass modifications.

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