Inpatient Rehab Facility Coding – Picking the Etiologic Diagnosis on the IRF-PAI

by Nirmala Sivakumar, CCS, CDIP

Inpatient rehab coding has always presented a challenge for HIM coders, even the ones that have many years of coding experience. Coding in an Inpatient Rehab Facility (IRF) setting is not limited to choosing ICD-10-CM codes. It also involves selecting the appropriate impairment group code (IGC), pairing it with the right etiologic diagnosis, and coding comorbid conditions and complications.

The etiologic diagnosis is the cause of a disease or abnormal condition. It is the condition that best explains the impairment for which the patient is admitted to an IRF as reported on the Patient Assessment Instrument (the IRF-PAI). It shouldn’t be a deficit or a symptom of the condition, but the condition itself. Once the physician determines why the patient is being admitted, it is the coder’s responsibility to choose the appropriate ICD-10-CM code for the etiologic diagnosis. It is typically an acute code. Code for late effects or sequelae are used as etiology only if the patient has completed prior rehabilitation for the same condition or impairment.

There is confusion in the industry as to how to choose the etiology. Since an IRF is considered post-acute care, coders follow the ICD-10-CM Official Guidelines for Coding and Reporting and typically assign aftercare codes or sequelae codes for the etiology.

However, these coding guidelines do not apply to coding the etiology on the IRF-PAI completed at admission to rehab. The coding guidelines for the IRF-PAI differ from the guidelines for the UB-04. Though the ICD-10-CM codes on these two documents must tell the same story on a patient, they don’t always match.

The etiologic diagnosis should be coded using IRF Prospective Payment System (PPS) guidelines. The IRF-PAI training manual published by Centers for Medicare and Medicaid Services (CMS) should be used as a reference when coding the etiology. The etiologic diagnosis on the IRF-PAI will also differ in most cases from the principal diagnosis on the UB-04.

For example: A 75 year old patient is admitted to an IRF with right sided dominant hemiplegia following an acute embolic stroke in the left MCA. The following table illustrates how the etiology should be coded and how it would differ from the principal diagnosis on the UB-04.

The complexities of IRF coding can be simplified if facilities provide rehab-specific training to their coders. This will help coders who code rehab cases to better grasp the nuances of IRF-PAI coding.


eLearning Library Subscription
Unlimited access to over 60 courses, assessments, and training curriculums designed to enhance job-specific, self-paced learning for one full year. Special pricing available for Groups. Train your entire team! Learn more here.


Nirmala Sivakumar, CDIP, CCS
Nirmala Sivakumar is an IRF Coding Educator based in PA. She has created and presented many webinars and workshops on IRF coding and improving clinical documentation. She has trained and mentored many rehab coders. She also has experience in conducting coding audits. She enjoys sharing her expertise and knowledge and has a desire to help coders and PPS Coordinators overcome the challenges of IRF PPS coding.

She has held previous positions as Health Information Management Supervisor for one of HealthSouth’s (Encompass) acute inpatient rehab hospital and as a HIM Coding Consultant at Uniform Data Systems for Medical Rehabilitation. She can be reached at [email protected] or visit

About the Author

Libman Education
Libman Education Inc. is a leading provider of training for the health care workforce offering self-paced and instructor-led online courses designed and developed by leading industry experts in Health Information Management (HIM) and Medical Record Coding. Our courses are specifically designed to improve individual skills and increase the efficiencies and competencies of health care providers and institutions. At Libman Education, we understand the needs and challenges of a well-trained workforce and offer the right-mix of online education to ensure that the health care professionals are prepared to meet the challenges of the changing workplace.

Comments are closed.