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HelpTest ID TULG Francisella tularensis Antibody, IgG, ELISA, Serum
Specimen Required
Only orderable as part of a profile. For more information see TULAB / Francisella tularensis Antibody, IgM and IgG, ELISA, Serum.
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
Evaluating the presence of IgG antibodies in patients with suspected 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.
Method Name
Only orderable as part of a profile. For more information see TULAB / Francisella tularensis Antibody, IgM and IgG, ELISA, Serum.
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name
F. tularensis Ab, IgG ELISA, SSpecimen Type
SerumSpecimen 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
Only orderable as part of a profile. For more information see TULAB / Francisella tularensis Antibody, IgM and IgG, ELISA, Serum.
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 infection with the various F tularensis subspecies.
Clinical Reference
1. Petersen JM, Schriefer ME, Araj GE. Francisella and Brucella. In: Carroll KC, Pfaller MA, Landry ML, et al, eds. Manual of Clinical Microbiology. 12th ed. AMS Press; 2019
2. Nigrovic LE, Wingerter SL. Tularemia. Infect Dis Clin North Am. 2008;22(3):489-504. doi:10.1016/j.idc.2008.03.004
Method Description
The enzyme-linked immunosorbent assay is an immunoassay that is particularly suited to the determination of antibodies in various kinds of samples. The reaction is based on the specific interaction of antibodies with their corresponding antigen. The test strips of the microtiter plate are coated with specific antigens of the pathogen of interest. If antibodies in the sample are present, they bind to the fixed antigen. A secondary antibody, which has been conjugated with the enzyme alkaline phosphatase detects and binds to the immune complex. The colorless substrate p-nitrophenylphosphate is then converted into the colored product p-nitrophenol. The signal intensity of this reaction product is proportional to the concentration of the analyte in the sample and is measured photometrically.(Package insert: Francisella tularensis IgG/IgM ELISA. Immuno-Biological Laboratories Inc.; V 142.6)
Day(s) Performed
Tuesday, Thursday
Report Available
Same day/1 dayTest 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