Aids in the diagnosis of leptospirosis
This is test is intended to be used as an aid for the diagnosis of acute or recent leptospirosis due to infection with Leptospira species.
This is a qualitative immunodot test for detection of IgM-class antibodies to Leptospira species.
A negative result by this assay does not exclude the possibility of leptospirosis and all results must be correlated with clinical presentation and exposure history.
Enzyme-Linked Immunoassay Dot (Immunodot)
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 0.3 mL
Collection Instructions: Serum should be collected according to standard practices. Acute and convalescent specimens obtained to determine seroconversion should be collected 2 or more weeks apart.
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
|Specimen Type||Temperature||Time||Special Container|
|Serum||Refrigerated (preferred)||30 days|
Aids in the diagnosis of leptospirosis
Leptospirosis is a zoonotic disease of worldwide prevalence, though the majority of infections occur in warm, tropical climates. Wild mammals, typically rodents, are the primary, natural reservoir for pathogenic strains of Leptospira, however, domestic animals (eg, dogs) also represent a major source of human infection. Leptospira are Gram-negative spirochetes with at least 20 different species in the genus. Of these, at least 9 species are considered pathogenic, including the most common agent of leptospirosis, Leptospira interrogans.
Transmission occurs through indirect human contact (eg, via mucous membranes or abraded skin) with water, food, or soil contaminated with animal urine containing the Leptospira spirochetes. Following infection, the incubation period can range from 3 to 30 days depending on the inoculum dose and immune status of the individual.
The clinical manifestations of leptospirosis can vary, ranging from a mild, flu-like illness (eg, headache, malaise, fever, arthralgia, fatigue) to fulminant disease, with severe liver and kidney involvement. The latter manifestation was previously referred to as Weil disease. Leptospira organisms may be found in the blood at the onset of disease and can persist for approximately 1 week. Subsequently, spirochetes may be found in the urine and can persist for 2 to 3 months; however, shedding may be intermittent and the numbers of organisms present may be low.
While Leptospira can be grown in culture, this is a fastidious organism and requires immediate transport to the laboratory. Additionally, detectable growth requires prolonged incubation (1-6 weeks), limiting the utility of culture for acute diagnosis. For this reason, serologic detection for antibodies to Leptospira remains the method of choice for rapid diagnosis. IgM-class antibodies to this spirochete are detectable by day 6 of illness and remain detectable for 2 to 3 months following symptom onset.
IgM antibodies to Leptospira species detected suggesting recent infection. Antibody presence alone cannot be used to definitively diagnose acute infection, as antibodies from a prior exposure or infection may remain detectable for a prolonged period of time.
Result should be interpreted with caution. Additional testing of a second, convalescent specimen is recommended. If the specimen remains borderline reactive, a second serological method should be considered if leptospirosis infection is still suspected.
No IgM antibodies to Leptospira detected. Since antibodies may not be present or may be present at undetectable levels during early disease, repeat testing of a convalescent sample collected in 2 to 3 weeks is recommended.
The temporal IgM immune response can vary among patients. Therefore, a single negative result by this assay should not be used to exclude diagnosis, especially in patients with symptoms suggestive of leptospirosis who have an appropriate exposure history.
This test does not distinguish between acute or past infection. Clinical correlation is required. Patients may remain seropositive for months to possibly years following resolution of disease; therefore, this test cannot be used to establish cure or response to therapy.
A total of 40 previously characterized serum samples tested by the Focus Diagnostics, Inc. Leptospirosis Indirect Hemagglutination Assay (IHA) (30 were positive and 10 were negative) were evaluated by the GenBio Leptospira IgM ImmunDOT assay. A summary of the results is provided below:
Comparison of the GenBio and Focus Diagnostics Leptospira assays
Focus IHA pos
Focus IHA neg
Positive Agreement: 100% (30/30); 95% Confidence Interval (CI) 86.5%-100%
Negative Agreement: 100% (10/10); 95% CI 67.9%-100%
Overall Agreement: 100% (40/40); 95% CI 89.5%-100%
1. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of High-Consequence Pathogens and Pathology (DHCPP): Leptospriosis. Reviewed March 13, 2019. Accessed October 16, 2020. Available at www.cdc.gov/leptospirosis/
2. Costa F, Hagan JE, Calcagno J, et al: Global morbidity and mortality of Leptospirosis: A systemic review. PLoS Negl Trop Dis. 2015 Sept;9(9):e0003898 doi: 10.1371/journal.pntd.0003898
The GenBio IgM ImmunoDOT Leptosirosis test utilizes an enzyme-linked immunoassay (EIA) dot technique for the detection of IgM antibodies. Leptospira biflexa, serovar Patoc 1 strain antigens are dispensed as discrete dots onto a solid membrane. After adding the test specimen to a reaction cuvette, an assay strip is inserted, allowing patient antibodies reactive with the test antigens to bind to the strip's solid support member. Alkaline phosphatase conjugated goat antihuman IgM antibodies are allowed to react with bound patient antibodies. Finally, the strip is transferred to an enzyme substrate reagent, which reacts with bound alkaline phosphatase to produce an easily seen, distinct spot.(Package insert: ImmunoDOT Leptospira IgM. GenBio;06/2019)
Monday, Wednesday, Friday
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.