Overview of IRF-PPS
The Inpatient Rehabilitation Facility Prospective Payment System (IRF-PPS) reimburses freestanding inpatient rehabilitation facilities and rehabilitation units based on Case Mix Groups (CMGs) rather than the MS-DRG system used for general acute care.
The IRF-PAI
Payment classification relies on the Inpatient Rehabilitation Facility Patient Assessment Instrument (IRF-PAI), which captures functional status, cognitive status, comorbidities, and the impairment group requiring rehabilitation. Functional independence scores at admission are a key driver of CMG assignment.
Case Mix Groups
- CMGs group patients by impairment category, functional status, age, and comorbidities
- Each CMG carries a relative weight similar in concept to MS-DRG weights
- Tiered comorbidity adjustments increase payment for patients with qualifying comorbid conditions that increase resource use
The 60 Percent Rule
To qualify for classification as an inpatient rehabilitation facility, at least 60 percent of a facility's total inpatient population must require intensive rehabilitation for one or more of 13 specified conditions established by CMS. This compliance threshold affects facility-level Medicare certification, not individual claim payment, but is an important related concept.
Coding Considerations
- Accurate ICD-10-CM coding of the impairment requiring rehabilitation and all relevant comorbidities
- Correct completion of functional status items on the IRF-PAI, which directly affects CMG assignment
- Documentation supporting medical necessity for the intensive rehabilitation level of care
Comparing IRF-PPS to Acute Care IPPS
Unlike IPPS, which relies primarily on diagnosis and procedure codes for DRG assignment, IRF-PPS payment depends heavily on functional assessment data collected by interdisciplinary rehabilitation staff, making accurate IRF-PAI completion as important as coding accuracy.
Exam Tip
Understand that post-acute PPS systems (IRF, SNF, home health) each use distinct patient assessment instruments to drive payment, and be able to name the assessment tool associated with each setting.