What is the definition of immunocompromised?

Definition of Immunocompromised

An immunocompromised host is a patient with an impaired or weakened immune system that does not allow normal responses to infections. 1 This can result from alterations in phagocytic, cellular, or humoral immunity, increasing the risk of infectious complications or opportunistic processes.

Categories of Immunocompromised Patients

Immunocompromised patients can be classified into the following categories:

1. Congenital Conditions

• T- or B-cell defects
• Macrophage dysfunctions
• Often present in newborns and children but can also affect adults 1

2. Acquired Conditions

• HIV infection with progression to AIDS 1
• Hematologic malignancies (leukemia, lymphoma, multiple myeloma) 1
• Solid organ transplant recipients requiring immunosuppressive medications 1
• Intrinsic immune conditions with concurrent solid malignancy, inflammatory/rheumatologic disease plus immunomodulatory drugs or chemotherapy 1
• Physiologic or pathologic conditions accompanied by any degree of immunodeficiency 1

Severity Classification

The Centers for Disease Control recognizes three categories of immunocompromised states based on severity 1:

1. Severely immunocompromised persons not due to HIV infection:

   • Congenital immunodeficiency
   • Leukemia, lymphoma, generalized malignancy
   • Therapy with alkylating agents, antimetabolites, radiation
   • High-dose corticosteroids (≥20 mg/day of prednisolone or ≥2 mg/kg body weight for ≥2 weeks) 1

2. Persons with HIV infection

3. Persons with conditions causing limited immune deficits:

   • Hyposplenism
   • Renal failure

Causes of Immunocompromise

Immunocompromise can result from:

• Medications:

  • Corticosteroids (≥20 mg/day of prednisolone for ≥2 weeks) 1
  • Thiopurines
  • Methotrexate
  • Calcineurin inhibitors
  • Anti-TNF agents and other biologics 1
  • Chemotherapy agents
  • Radiation therapy

• Disease states:

  • Primary immunodeficiencies
  • HIV/AIDS
  • Malignancies (especially hematologic)
  • Autoimmune conditions

Clinical Implications

Immunocompromised patients:

• May present with atypical or minimal symptoms of infection 1
• Are at increased risk for opportunistic infections 1
• May have diminished response to vaccinations 1
• Often require multidisciplinary management 1
• May need specialized infection control measures

Risk Stratification

Patients can be stratified based on their immunocompromised status 1:

• Class A: Healthy patients with no or well-controlled comorbidities and no immunocompromise
• Class B: Patients with major comorbidities and/or moderate immunocompromise but clinically stable
• Class C: Patients with advanced comorbidities and/or severe immunocompromise

Important Considerations

• There is no single method to quantify the degree of immunosuppression 1
• Combination immunosuppressive therapy increases infection risk 1
• Age, malnutrition, and comorbidities are additional risk factors for infections in immunocompromised patients 1
• Household contacts of immunocompromised patients should be appropriately immunized to reduce exposure risk 1

Understanding the definition and classification of immunocompromised patients is essential for appropriate risk assessment, preventive strategies, and management of infections in this vulnerable population.