Introduction to APR-DRG
All Patient Refined Diagnosis Related Groups, known as APR-DRG, are a classification system used primarily by state Medicaid programs and some commercial payers to more precisely account for patient severity than the standard Medicare Severity DRG system. RHIA candidates should understand how APR-DRG subclasses refine reimbursement and reporting beyond a simple base DRG assignment.
Structure of APR-DRG
Each APR-DRG base group is subdivided into four severity of illness subclasses and four risk of mortality subclasses, ranging from minor to extreme. This means a single base DRG can be split into sixteen possible combinations, allowing much finer differentiation of resource intensity and clinical risk than the three-tier structure used in Medicare Severity DRGs.
Severity of Illness Versus Risk of Mortality
Severity of illness reflects the extent of physiologic decompensation or organ system dysfunction a patient experiences, essentially measuring how sick the patient is and how much clinical resource intensity that condition requires. Risk of mortality reflects the likelihood of death, which can differ from severity of illness; a patient can have a high risk of mortality from a chronic, stable condition without currently exhibiting severe acute physiologic decompensation.
How Secondary Diagnoses Affect Subclass Assignment
- Each secondary diagnosis is assigned an individual severity level based on its own clinical significance
- The interaction between multiple secondary diagnoses can increase the overall severity subclass beyond what any single diagnosis would produce alone
- Age and certain procedures can also influence the final subclass determination
Why Documentation Precision Matters
Because APR-DRG subclass assignment is highly sensitive to the specificity and completeness of secondary diagnosis documentation, clinical documentation improvement programs place significant emphasis on capturing the full extent of a patient's comorbidities and complications to ensure accurate severity and mortality risk classification.
Applications Beyond Reimbursement
Even in settings where APR-DRG does not directly determine payment, hospitals often use the severity and mortality subclasses for internal quality benchmarking, since they allow more meaningful comparison of outcomes like mortality rate or length of stay across patients with genuinely different clinical risk profiles.
Exam Tip
Remember that APR-DRG produces two separate subclass scores, severity of illness and risk of mortality, and be ready to explain why these two dimensions can diverge for the same patient.