Immunocompromised Host Pneumonia: Definitions and Diagnostic Criteria: An Official American Thoracic Society Workshop Report

Abstract

Pneumonia imposes a significant clinical burden on people with immunocompromising conditions. Millions of individuals live with compromised immunity because of cytotoxic cancer treatments, biological therapies, organ transplants, inherited and acquired immunodeficiencies, and other immune disorders. Despite broad awareness among clinicians that these patients are at increased risk for developing infectious pneumonia, immunocompromised people are often excluded from pneumonia clinical guidelines and treatment trials. The absence of a widely accepted definition for immunocompromised host pneumonia is a significant knowledge gap that hampers consistent clinical care and research for infectious pneumonia in these vulnerable populations. To address this gap, the American Thoracic Society convened a workshop whose participants had expertise in pulmonary disease, infectious diseases, immunology, genetics, and laboratory medicine, with the goal of defining the entity of immunocompromised host pneumonia and its diagnostic criteria.

Keywords: diagnosis; immunocompromised host; immunosuppression; pneumonia.

Figure 1.

Diagnostic criteria and algorithm for pneumonia in a host with a known immune defect. Clinical signs and symptoms include fever, cough, sputum production, as well as hypoxemia, which should prompt evaluation with chest imaging. In the immunocompromised host, lung infiltrates may not be evident by chest X-ray and may require a computed tomography scan for detection. It should be noted that immunocompromised hosts may have concurrent and multiple infectious and noninfectious etiologies of lung infiltrates (e.g., viral pneumonia, invasive aspergillosis, and congestive heart failure). ICH = immunocompromised hosts.

Figure 2.

Diagnostic criteria and algorithm for pneumonia in a host without a known immune defect. In this scenario, an opportunistic pathogen is detected in a patient with radiographic infiltrates. Underlying immunocompromise may also be suspected with an unusual radiographic presentation that suggests an opportunistic infection (e.g., cystic lesions as a presentation of Pneumocystis pneumonia). ICH = immunocompromised hosts.