Lab Test

Antigen, Legionella Urinary

Legionnaire’s Disease, Atypical Pneumonia

Test Codes

EPIC: LAB2234

Department

Microbiology

Specimen Collection Criteria

Collect (preferred specimen): Random urine in a sterile collection cup or Gray-top Boric Acid urine tube. (Minimum: 3.0 mL)

Physician Office/Draw Specimen Preparation

Maintain specimen in sterile collection cup refrigerated (2-8°C or 36-46°F) prior to courier pickup (Minimum: 3.0 mL).  

Maintain gray-top urine tube at room temperature (20-26°C or 68-78.8°F) prior to courier pickup (Minimum 3.0 mL). 

Preparation for Courier Transport

Transport:  Sterile collection cup: refrigerated (2-8°C or 36-46°F).

Gray-top urine tube at room temperature (20-26°C or 68-78.8°F). 

Rejection Criteria

Preservatives other than boric acid.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): 14 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 4 days

Laboratory

Dearborn Microbiology Laboratory
Taylor, Trenton and Wayne sent to Dearborn Microbiology Laboratory for testing.
Farmington Hills Microbiology Laboratory
Grosse Pointe Microbiology Laboratory
Royal Oak Microbiology Laboratory
Troy Microbiology Laboratory  

Performed

Sunday – Saturday, 24 hours a day.

Reference Range

Ratio Result
Presumptive positive for the presence of L. pneumophila serogroup 1 antigen in urine, suggesting current or past infection.

Presumptive negative for L. pneumophila serogroup 1 antigen in urine, suggesting no recent or current infection with that organism. Legionnaires disease cannot be ruled out since other serogroups and species may also cause disease.

Test Methodology

Immunochromatographic Assay.

Interpretation

NOTE: This test only detects Legionella pneumophila serogroup 1.

The Legionella urinary antigen may be excreted as early as 3 days after the onset of symptoms and may persist for up to 1 year. Persistence of antigen for prolonged periods can make it difficult to distinguish a previous infection from a current infection. It is not a definitive diagnosis of legionellosis without other supporting evidence.

Early treatment with appropriate antibiotics may decrease antigen excretion in some patients causing false-negative results. Diuretic urine may produce a dilution-effect which, in turn, contributes to false-negative results.

Clinical Utility

This test is used to qualitatively detect the presence of Legionella pneumophila serogroup 1 antigen in human urine and can be used as an adjunct to culture for the presumptive diagnosis of past or current Legionnaires' disease. This test is used to qualitatively detect the presence of Legionella pneumophila serogroup 1 antigen in human urine and can be used as an adjunct to culture for the presumptive diagnosis of past or current Legionnaires' disease.

Clinical Disease

Legionellosis has two forms. Legionnaires' disease and the milder infection, Pontiac fever. Although a multisystemic disease, the predominant clinical finding in patients with Legionnaires' disease is pneumonia. Patients usually have fever, malaise, anorexia, chills, and a cough. Chest x-rays often show pneumonia. Pontiac fever is an acute, self-limiting, flu-like illness without pneumonia. Symptoms include malaise, myalgias, fever, chills, headache, and a nonproductive cough. The chest x-ray is clear.

Disease Reporting

This is a reportable disease and positive results will be reported to the local county health department. For more information on reportable diseases, contact the Epidemiology Department.

Epidemiology

10,000 to 15,000 persons get Legionnaires' disease in the U.S. each year. The disease occurs more frequently in males and rarely affects children. Outbreaks of Legionnaire's disease usually occur in the summer and early fall, but cases can occur year round.

Incubation Period

The incubation period for Legionnaires's disease is 2 to 10 days. The incubation period for Pontiac fever is 24-48 hours.

Transmission

The primary mode of transmission is airborne. L. pneumophila has been isolated from water-cooling towers or evaporative condensers in air-conditioning systems, contaminated plumbing fixtures and from soil.

Reference

  1. Edelstein, P.H. 2011. Legionella. Manual of Clinical Microbiology. Versalovic, J. et al. (eds.). ASM Press. Washington, D.C.

CPT Codes

87450
LOINC:  6447-7

Contacts

Last Updated

6/30/2021

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