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Legionella Antibody, Serum

Test Codes

Epic: LAB6498, Beaker: XMISC, Mayo: SLEG

Department

Send Outs

Specimen Collection Criteria

Collect (preferred specimens): Two Gold-top SST tube.
Also acceptable: One plain Red-top tube.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Preparation for Courier Transport

Transport: 0.5 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 0.4 mL)

Rejection Criteria

• Hemolyzed specimens.
• Severely lipemic specimens.
• Specimens that have been heat-activated.

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Transport: 0.5 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 0.4 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Unacceptable
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:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Mayo Medical Laboratories, Rochester, MN.

Performed

Wednesday.
Results available in 2-6 days.

Reference Range

By report.

Test Methodology

Enzyme-Linked Immunosorbent Assay (ELISA).

Interpretation

A negative result indicates that IgG, IgA, and IgM antibody to Legionella pneumophila serogroups 1-6 was not detected. Negative results do not exclude Legionella infection. It may require 4 to 8 weeks to develop a detectable antibody response; serum specimens taken early in the course of infection may not yet have significant antibody titers. Furthermore, antibody levels can fall to undetectable levels within a month of infection, early antibiotic therapy may suppress antibody response, and some individuals may not develop antibodies above detectable limits.

Some culture-positive cases of Legionella do not develop Legionella antibody.

Positive results are suggestive of Legionella infection. A positive result only indicates immunologic exposure at some point in time. It does not distinguish between previous or current infection. The level of antibody response may not be used to determine active infection. Other laboratory procedures or additional clinical information are necessary to establish a diagnosis.

Specimens with equivocal results are retested prior to reporting. Repeat testing on a second specimen should be considered in patients with equivocal results, if clinically indicated.

Clinical Utility

Evaluation of possible legionellosis (Legionnaires disease, Pontiac fever, extrapulmonary legionella infection caused by Legionella pneumophila).

Clinical Disease

Legionellosis has two forms. Legionnaires' disease and the milder infection Pontiac fever. 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, flulike 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 infection and positive results will be reported to the Oakland County Health Department. For more information on reportable diseases, contact the BH Epidemiology Department at 248-551-4040.

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. Detection of antibodies to Legionella spp. In Rose, et al. Manual of Clinical Laboratory Immunology, Fifth Edition, 1997;503.
2. Edelstein P. Detection of antibodies to Legionella. In Rose, et al. Manual of Clinical Laboratory Immunology, Fourth Edition, 1992;459-466.

CPT Codes

86713

Contacts

Last Updated

7/21/2024