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Test Code TULAB Francisella tularensis Antibody, IgM and IgG, ELISA, Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.6 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


Useful For

Aiding in the diagnosis of tularemia caused by Francisella tularensis

 

This test should not be used as a test of cure as it is not quantitative. Patients may remain seropositive for months to years following resolution of disease.

Profile Information

Test ID Reporting Name Available Separately Always Performed
TULM F. tularensis Ab, IgM ELISA, S No Yes
TULG F. tularensis Ab, IgG ELISA, S No Yes
TULI F. tularensis Interpretation No Yes

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Reporting Name

F. tularensis Ab, IgM/IgG ELISA, S

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  30 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Heat inactivated specimen Reject

Clinical Information

Francisella tularensis is a small, intracellular, coccobacillary gram-negative bacterium and is an obligate pathogen in animals and humans, primarily maintained in rabbits, hares, cats, ticks, and deerflies. F tularensis is found throughout North America and parts of Asia and, similar to Brucella species, is considered a potential agent of bioterrorism. Human infection with F tularensis usually occurs through inhalation of infected aerosols, ingestion of contaminated meat or water, handling of diseased or sick animals, or through the bite of an infected arthropod (eg, tick, deerflies).

 

Following a 3- to 5-day incubation period, the clinical manifestations of infection with F tularensis differ primarily depending on the site and route of infection. The most common form of disease is ulceroglandular (45%-80% of cases), which is associated with an arthropod (or animal) bite or another cause of skin barrier compromise. This leads to development of a painful papule that ultimately ulcerates allowing the bacterium to enter the lymphatic system. Glandular tularemia is similar in presentation to ulceroglandular disease; however, it lacks the ulceration and, more frequently, causes septicemia. Other, less frequent clinical manifestations include oculoglandular (Parinaud syndrome), oropharyngeal and gastrointestinal disease, and pneumonic or typhoidal tularemia.

 

Diagnostic testing options for F tularensis primarily include culture and serology. Providers suspecting tularemia should collect appropriate specimens (eg, skin lesion biopsy, lymph node aspirates) promptly and send for culture. The microbiology laboratory should be alerted to the possibility of F tularensis to ensure that appropriate safety measures are taken to protect the laboratory technologists. Growth on culture is a definitive means of making a diagnosis of tularensis. Serologic testing may be used to support a diagnosis of current or recent tularensis in patients who are IgM positive, who seroconvert to IgM, or who are IgG positive in paired sera collected 2 to 3 weeks apart.

Reference Values

Negative

 

Reference values apply to all ages.

Interpretation

IgM result

IgG result

Interpretation

Negative

Negative

No antibodies to Francisella tularensis detected. Antibody response may be negative in samples collected too soon following infection/exposure. Repeat testing on a new sample in 1 to 2 weeks if clinically indicated.

Positive

Negative

IgM class antibodies to F tularensis detected, suggesting current or recent infection. Repeat testing in 1 to 2 weeks to detect seroconversion of IgG may be considered to confirm the diagnosis.

Positive

Borderline

Borderline

Negative

Questionable presence of IgM antibodies to F tularensis. Consider repeat testing in 1 to 2 weeks.

Borderline

Positive

IgG class antibodies to F tularensis detected suggesting recent or past infection. Clinical correlation alongside presentation, exposure history and other laboratory findings required.

Borderline

Borderline

Questionable presence of IgM and IgG class antibodies to F tularensis. Consider repeat testing in 1 to 2 weeks.

Positive

Positive

IgM and IgG class antibodies to F tularensis detected suggesting current, recent or past infection. Cross-reactions may occur in patients with a current or prior Brucella infection. Clinical correlation alongside presentation, exposure history and other laboratory findings required.

Negative

Positive

IgG class antibodies to F tularensis detected suggesting recent or past infection. Clinical correlation alongside presentation, exposure history and other laboratory findings required.

Negative

Borderline

Questionable presence of IgG antibodies to F tularensis. Consider repeat testing in 1 to 2 weeks.

Cautions

False-negative results may occur in specimens collected too soon following symptom onset, prior to the development of a detectable immune response. Repeat testing on new specimens collected 2 to 4 weeks later may be helpful.

 

False-positive results may occur in patients previously or currently infected with Brucella species. Other less frequent causes of cross-reactivity that have been reported include prior infection with Yersinia, Salmonella, or Legionella species.

 

IgM-class antibodies may be detectable as soon as 1 week after symptom onset and may remain detectable for multiple years following resolution of disease in some individuals. Therefore, an IgM-positive result may not indicate current or recent infection in some cases.

 

Multiple subspecies of Francisella tularensis, including F tularensis subspecies tularensis, F tularensis subspecies holarctica, and F tularensis subspecies novicida are found throughout the northern hemisphere, including in the United States. The IgM and IgG anti-F tularensis enzyme-linked immunosorbent assays used at Mayo Clinic Laboratories are based on the lipopolysaccharide (LPS) antigen of F tularensis. Although not directly tested, previous studies indicate that there are no antigenic differences between the LPS of F tularensis subspecies tularensis and the other subspecies. Therefore, these assays should not be used to differentiate between infections with the various F tularensis subspecies.

Day(s) Performed

Tuesday, Thursday

Report Available

Same day/1 to 7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US 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

86668 x 2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TULAB F. tularensis Ab, IgM/IgG ELISA, S 93715-1

 

Result ID Test Result Name Result LOINC Value
TULM F. tularensis Ab, IgM ELISA, S 93716-9
TULG F. tularensis Ab, IgG ELISA, S 93717-7
TULI F. tularensis Interpretation 93718-5

Forms

If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.