Here’s how to accurately code for immunosuppression and immunodeficiency

Patients on immunosuppressant medications are commonly assigned a diagnosis code for immunodeficiency. However, in the American Hospital Association’s manual on ICD-10-CM codes, immunosuppression and immunodeficiency are not synonymous. They’re represented by distinctly different ICD-10-CM codes.

Immunodeficiency
Immunodeficiency is caused by a malfunction of the immune system. This malfunction can be either congenital (primary) or acquired.

Congenital immunodeficiency
There are more than 100 primary immunodeficiency disorders, classified by the specific part of the immune system they affect. Examples include:

• Common variable immunodeficiency
• Bruton’s disease
• Severe mixed immunodeficiency syndrome
• Deficiency of a specific antibody
• Cyclic neutropenia

Acquired immunodeficiency
This can occur in one of two ways:

1. As a side effect or adverse effect of a medication that’s correctly prescribed and properly administered. The medicine is used to treat an underlying disease without the intent to alter the immune state, such as antineoplastic chemotherapy drugs or radiation.**
   
   Example: The physician documents that the patient is immune deficient due to chemotherapy used for treating cancer. The correct code assignment would be T45.1X5-, adverse effect of antineoplastic and immunosuppressive drugs. The required 7th digit is dependent on if the patient is receiving active treatment (A), routine care during the healing or recovery phase (D) or treatment for complications or conditions that arise directly from the condition (S).
   
   
2. As the result of a disease or disorder, such as:
• Cancer
• A human immunodeficiency virus infection leading to acquired immunodeficiency syndrome, or AIDS

Immunosuppression
Immunosuppression is caused by medications prescribed to intentionally suppress the immune system. These medications are used to treat various autoimmune diseases, including:

• Rheumatoid arthritis
• Sjogren’s syndrome
• Psoriasis
• Crohn’s disease

By suppressing the overreactive immune system in patients with these conditions, the immune response triggering the disease process is weakened. Weakening the immune response helps promote remission in afflicted patients.

Immunosuppressant medications are also required for patients who have had an organ transplant. Since the immune system is designed to attack anything foreign within our body, transplanted organs are no exception. By suppressing the immune system, the body is less likely to reject the transplanted organ.

Example: A physician documents that a patient has an immune deficiency and is taking immunosuppressants. The doctor should use code Z79.899 to represent the patient’s long-term immunosuppressant medication therapy. The ICD-10-CM code for immunodeficiency doesn’t provide a specific code to identify these drugs. Since this patient is taking the immunosuppressant medication, with the intent to suppress the immune system, codes for immunodeficiency that’s caused by an adverse effect of drug treatment or from an underlying disease should not be assigned.**

**AHA Coding Clinic for ICD; 2015; third quarter