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Legionella urinary antigen in early disease
S Bernander1, B Gästrin, S Löfgren
1Department of Clinical Microbiology, Karolinska Hospital, Stockholm, Sweden.
Scandinavian Journal of Infectious Diseases
|January 1, 1994
Summary
Legionella urinary antigen tests may be negative early in Legionnaires' disease. Testing urine within the first five days of illness risks false negatives, impacting diagnosis during outbreaks.
Area of Science:
- Infectious Diseases
- Microbiology
- Public Health
Background:
- Legionnaires' disease is a severe pneumonia caused by Legionella bacteria.
- Early and accurate diagnosis is crucial for effective treatment and outbreak control.
- Legionella urinary antigen testing is a common diagnostic method.
Purpose of the Study:
- To evaluate the accuracy of Legionella urinary antigen testing based on the timing of urine sample collection relative to disease onset.
- To determine the impact of the interval between illness onset and sampling on test sensitivity.
Main Methods:
- A correlation study was conducted on 134 patients during a large Legionnaires' disease outbreak.
- Urine samples were tested for Legionella urinary antigen.
- The timing of sample collection in relation to the onset of symptoms was recorded.
Main Results:
- Out of 17 patients with confirmed Legionnaires' disease, 5 out of 7 tested during the first 5 days of illness yielded negative results for the urinary antigen.
- This indicates a reduced sensitivity of the test in the early stages of the disease.
Conclusions:
- Legionella urinary antigen testing may produce false-negative results when performed within the first five days of illness.
- Clinicians should be aware of the risk of false negatives, especially during the early phase of Legionnaires' disease.
- Diagnostic strategies may need to consider the timing of sample collection to improve detection rates.