What are the urine studies for pneumonia (PNA)?

From the Guidelines

Urine studies for pneumonia (PNA) should include a urine antigen test for Legionella pneumophila or Streptococcus pneumoniae, particularly in patients admitted to the hospital for reasons of illness severity or when these specific pathogens are suspected, as recommended by the guidelines for the management of adult lower respiratory tract infections 1.

Key Points:

• The Legionella urinary antigen test detects antigens from Legionella pneumophila serogroup 1, which causes approximately 80-90% of Legionella pneumonia cases.
• The pneumococcal urinary antigen test detects C-polysaccharide cell wall antigens from Streptococcus pneumoniae.
• These tests provide rapid results (within 15-30 minutes) and can be useful when patients have already started antibiotics or when obtaining adequate respiratory samples is difficult.
• The sensitivity of these tests ranges from 70-80% with specificity over 95%, as reported in the guidelines for the management of community-acquired pneumonia in adults 1.
• Urine antigen testing appears to have a higher diagnostic yield in patients with more severe illness, as noted in the infectious diseases society of america/american thoracic society consensus guidelines on the management of community-acquired pneumonia in adults 1.

Considerations:

• The value of the S. pneumoniae urinary antigen test in adults has a sensitivity of 65–100% and a specificity of 94%, but weak positive results should be interpreted with caution 1.
• A positive result of the urinary antigen test is associated with a more severe clinical course and leads to a potential relevant under-recognition of species other than L. pneumophila, as demonstrated in the CAPNETZ study 1.
• The urinary antigen test may also be carried out on pleural fluid with a sensitivity and specificity of 79% and 94%, respectively, and on serum samples with a sensitivity of 50% in bacteraemic patients and 40% in non-bacteraemic patients 1.

Recommendations:

• The immunochromatographic urinary antigen test for S. pneumoniae should be performed in patients admitted to the hospital for reasons of illness severity, as recommended by the guidelines for the management of adult lower respiratory tract infections 1.
• Urine L. pneumophila serogroup 1 antigen detection should be performed in patients admitted to the hospital for reasons of severity and in other patients where this infection is clinically or epidemiologically suspected, as noted in the guidelines for the management of adult lower respiratory tract infections 1.

From the Research

Urine Studies for Pneumonia (PNA)

• Urinary antigen tests (UATs) are used to detect Streptococcus pneumoniae and Legionella pneumophila in patients with pneumonia 2, 3, 4, 5, 6
• These tests are quick, simple, and non-invasive, with high specificity (>90%) and moderate sensitivity (<80%) 3
• The ImmuView Streptococcus pneumoniae and Legionella pneumophila Urinary Antigen Test is a fast and sensitive point of care test for identification of the infectious agent in patients with pneumonia 2, 5
• The BinaxNOW S. pneumoniae and L. pneumophila UATs are also commonly used for the diagnosis of pneumococcal and Legionella infections 3, 5, 6
• Urinary antigen testing can help guide antibiotic treatment and improve antimicrobial stewardship, especially in patients with severe community-acquired pneumonia (CAP) and those with epidemiological risk factors for Legionella 3
• However, current guidelines argue against the routine use of urinary antigen testing for S. pneumoniae and L. pneumophila, except in specific situations 3, 4
• The sensitivity and specificity of urinary antigen tests can vary depending on the test used and the population being tested, with reported sensitivities ranging from 62% to 71.4% and specificities ranging from 97% to 98.3% 2, 5, 6