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HelpTest ID SLEG Legionella pneumophila (Legionnaires Disease), Antibody, Serum
Useful For
Evaluation of possible legionellosis (Legionnaires disease, Pontiac fever, extrapulmonary legionella infection caused by Legionella pneumophila)
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name
Legionella Pneumophila Ab, SSpecimen Type
SerumCollection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 0.5 mL
Specimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 14 days |
| Frozen | 14 days |
Clinical Information
Legionella pneumophila may cause pulmonary disease in both normal and immunocompetent hosts. The disease may occur sporadically in the form of community acquired pneumonia and in epidemics. Pneumonia (often referred to as Legionnaires disease) occurs more frequently in severely immunosuppressed individuals; a milder form of the illness, referred to as Pontiac fever, is more prevalent in normal hosts. Extrapulmonary infection with Legionella pneumophila is rare. Legionnaire's disease, Pontiac fever, and extrapulmonary infection have been collectively referred to as legionellosis.
Approximately 85% of the documented cases of legionellosis have been caused by Legionella pneumophila. Serogroups 1 and 6 of Legionella pneumophila, by themselves, account for up to 75% of cases of legionellosis.
The definitive diagnosis of Legionella pneumophila is made by isolation of the organism on specialized culture medium (buffered charcoal yeast extract agar). Pulmonary secretions can be directly examined using a direct fluorescent antibody procedure, but the sensitivity of this method is low (25%-70%). Often it is difficult for the patient to produce pulmonary secretion (sputum) for examination, the pneumonia is frequently interstitial and sputum is scant. In the absence of invasive procedures (eg, bronchial alveolar lavage), urine evaluation for Legionella pneumophila antigen or indirect serological (antibody) methods may be useful.
Reference Values
Negative
Cautions
A diagnosis should not be made on the basis of positive Legionella antibody results alone. Test results for Legionella antibodies should be interpreted in conjunction with the clinical evaluation and the results of other diagnostic procedures.
A positive result suggests infection with 1 or more of the groups 1-6 species; however, one will not be able to distinguish between species with the results of this enzyme-linked immunosorbent assay (ELISA) test alone.
Use of serogroups 1-6 for assessing antibody responses to different Legionella species and serogroups has not been established.
Cross-reactivity may occur in sera with infections due to other Legionella species.
Positive results may be due to cross-reactivity with antibody generated as a result of non-Legionella infection. Serologic cross-reactions have been reported with Pseudomonas aeruginosa, several Rickettsia species, Coxiella burnetii, enteric gram-negative rods, Bacteroides species, Haemophilus species, Citrobacter freundii, and Campylobacter jejuni. Additionally, some reports indicate that a number of apparently healthy individuals may carry antibodies to legionellae; however, a positive result, along with clinical signs and symptoms may indicate possible Legionella infection. Additional serologic testing, such as paired sera analysis by immunofluorescence assay (IFA), or other clinical testing such as direct fluorescent antibody (DFA) and culturing, may be necessary to establish diagnosis.
The assay performance characteristics have not been established for matrices other than sera.
Although the conjugate is designed to detect human IgG, IgM, and/or IgA, one will not be able to determine which antibody is present with this assay.
The affinity and/or avidity of the anti-IgG/IgM/IgA conjugate has not been determined.
The use of hemolytic, lipemic, bacterially contaminated, or heat-inactivated specimens should be avoided. Erroneous results may occur.
Day(s) Performed
Tuesday, Thursday; 2 p.m.
Report Available
Same day/1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
86713