What Is APR-DRG?
All Patient Refined Diagnosis Related Groups, known as APR-DRG, is a patient classification system developed to more accurately reflect clinical severity across all patient populations, not just the Medicare population. APR-DRG is widely used by state Medicaid programs and many commercial payers for inpatient reimbursement and quality reporting.
Differences from MS-DRG
While MS-DRG was developed specifically for the Medicare population, which is predominantly older adults, APR-DRG was designed to classify patients of all ages, including neonates, children, and obstetric patients, making it more suitable for non-Medicare populations such as Medicaid beneficiaries and commercially insured patients. APR-DRG also incorporates a more granular severity classification system than the three-tier CC and MCC structure used in MS-DRG.
Severity of Illness Subclasses
Each APR-DRG base group is divided into four severity of illness subclasses, reflecting the extent of physiologic decompensation or organ system dysfunction:
- Minor
- Moderate
- Major
- Extreme
Severity of illness is determined by evaluating the combination of secondary diagnoses and their interaction with the principal diagnosis and patient age.
Risk of Mortality Subclasses
In addition to severity of illness, APR-DRG assigns a separate risk of mortality subclass, also divided into minor, moderate, major, and extreme categories. Risk of mortality reflects the likelihood of death associated with the patient's clinical profile, which may differ from the severity of illness classification since a condition can be resource-intensive without necessarily carrying high mortality risk, or vice versa.
Why Two Separate Classifications Matter
Having distinct severity of illness and risk of mortality subclasses allows APR-DRG to more precisely capture two related but distinct clinical dimensions: how sick and resource-intensive the patient's condition is during the encounter, versus how likely the patient is to die as a result of that condition. This dual classification is particularly valuable for quality reporting and mortality benchmarking.
Payer Applications
Many state Medicaid programs use APR-DRG as the basis for inpatient hospital reimbursement, particularly for pediatric and obstetric populations that MS-DRG does not classify well. APR-DRG is also frequently used in publicly reported severity-adjusted quality data, such as risk-adjusted mortality and complication rates published by state hospital associations.
Coding Implications
As with MS-DRG, accurate and specific documentation and coding of secondary diagnoses directly affects both severity of illness and risk of mortality subclass assignment under APR-DRG, making thorough capture of comorbidities essential.
Conclusion
The APR-DRG system extends refined patient classification beyond the Medicare population, using separate severity of illness and risk of mortality subclasses to support accurate reimbursement and quality benchmarking across diverse patient populations.