Test Catalog

Test ID: LEPDT    
Leptospira, IgM, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Aids in the diagnosis of leptospirosis

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Interpretation Provides information to assist in interpretation of the test results

Positive: 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.

 

Borderline: 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.

 

Negative: 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.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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.

Supportive Data

Accuracy:

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

ImmunoDOT Pos

30

0

ImmunoDOT Neg

0

10

 

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%

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. CDC: Leptospriosis. Accessed 12/30/16. 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) doi: 10.1371/journal.pntd.0003898

3. Package Insert: ImmunoDot Leptospira IgM, GenBio, San Diego, CA; Version 4.0