Legionella Pneumonia Undetected by Repeated Urinary Antigen Testing With Ribotest® Legionella.

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Pulmonary Medicine

Background:

• Legionella pneumonia (LP) is a severe respiratory infection.
• Accurate and timely diagnosis is essential for effective treatment.
• Urinary antigen tests are commonly used for LP diagnosis.

Observation:

• A patient presented with symptoms of pneumonia, progressing to severe illness.
• Multiple Ribotest® Legionella urinary antigen tests yielded negative results.
• Diagnosis was confirmed using loop-mediated isothermal amplification (LIA) on respiratory secretions.

Findings:

• The Ribotest® Legionella assay demonstrated diagnostic limitations in this case.
• LIA of lower respiratory tract secretions provided a definitive diagnosis.
• This highlights potential false-negative results with urinary antigen testing.

Implications:

• Clinicians should be aware of the limitations of urinary antigen tests for Legionella.
• Consider nucleic acid amplification tests or culture in suspected LP cases, especially with negative antigen tests.
• Comprehensive diagnostic strategies are vital for improving patient outcomes in Legionella pneumonia.