Question

1. What is the prevalence of pneumonia in immunocompromised persons?

Answer 1

Pneumonia in the immunocompromised host is a complex infection and inflammation of the lower respiratory tract, complicated by widespread multi-drug antibiotic resistance, and aided by medical advances such as improvements in diagnostic measures and immunosuppressive agents. Though overall patient survival has increased, pneumonia is both the most common invasive infection in immunocompromised patients and continues to carry a high mortality and morbidity rate.

The major immunocompromised host groups are those with:

• HIV/AIDS

• Solid organ and hematopoietic cell transplants

• Malignancy on chemotherapy or radiation therapy

• Primary immunodeficiencies and autoimmune diseases

• Acquired immunodeficiencies: asplenia, long-term steroid use

The diagnosis and identification of causative microorganisms of pneumonia are often difficult in immunocompromised patients.

• Immunosuppression can divided into three categories; neutropenia (or neutrophil dysfunction); humoral immunodeficiency and cellular immunodeficiency. Presumptive pathogen identifications of pneumonia could be made systematically based on the type of impaired immune function.

• Since there are a number of diseases that must be differentiated, the collection of respiratory tract specimens and appropriate serum antigen tests should be done whenever possible to identify the causative microorganisms.

• Empirical antibiotic therapy should be started as soon as possible.

• If initial treatment proves ineffective, invasive diagnostic procedures, including surgical lung biopsy, should be considered.

The major categories of immunosuppression are neutropenia (or neutrophil dysfunction), humoral immunodeficiency and cellular immunodeficiency.

Immunocompromised patients, however, often have more than two of those categories of immunosuppression in clinical settings.

Pneumonia is the most common infectious disease for the immunocompromised host because the lungs could be the portal of entry for a wide range of pathogens via respiration. The diagnosis of pneumonia and identification of causative organisms are often complicated because radiographical imaging findings and clinical symptoms of pneumonia could be different from those of immunocompetent patients as a result of immunosuppression.

Prevalence of Risk Factors for Immunocompromise

Among 3702 patients enrolled in the GLIMP database, ≥1 risk factor for immunocompromise was identified in 652 (17.6%). The prevalences of patients with pneumonia coming from the community and with ≥1 risk factor for immunocompromise differed among continents and countries.The prevalence of immuno-compromise was significantly higher in both North and South America than in the rest of the world (24.0% vs 16.5 [P<.001] and 24.8% vs 17.2 [P=.006], respectively) .  

The prevelence of each risk factor for immunocompromise with chronic steroid use (45.0%), hema-tological cancer (25.0%), and chemotherapy (22.0%) being the most frequent ones. A total of 312 patients (8.4) had ^1 risk factor for immunocompromise