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Test Code MISC2MAYOBABG Babesia microti IgG Antibodies, Serum

Reporting Name

Babesia microti IgG Ab, S

Useful For

An adjunct in the diagnosis of babesiosis


Follow-up of documented babesiosis

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  14 days

Reference Values


Reference values apply to all ages.

Day(s) Performed

Monday through Friday

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
BABG Babesia microti IgG Ab, S 16117-4


Result ID Test Result Name Result LOINC Value
81128 Babesia microti IgG Ab, S 16117-4

Clinical Information

Babesiosis is a zoonotic infection caused by the protozoan parasite Babesia microti. The infection is acquired by contact with Ixodes ticks carrying the parasite. The deer mouse is the animal reservoir and, overall, the epidemiology of this infection is much like that of Lyme disease. Babesiosis is most prevalent in the Northeast, upper Midwest, and Pacific Coast of the United States.


Infectious forms (sporozoites) are injected during tick bites and the organism enters the vascular system where it infects red blood cells (RBC). In this intraerythrocytic stage, it becomes disseminated throughout the reticuloendothelial system. Asexual reproduction occurs in RBC, and daughter cells (merozoites) are formed that are liberated on rupture (hemolysis) of the RBC.


Most cases of babesiosis are probably subclinical or mild, but the infection can be severe and life threatening, especially in older or asplenic patients. Fever, fatigue, malaise, headache, and other flu-like symptoms occur most commonly. In the most severe cases, hemolysis, acute respiratory distress syndrome, and shock may develop. Patients may have hepatomegaly and splenomegaly.


A serologic test can be used as an adjunct in the diagnosis and follow-up of babesiosis, when infection is chronic or persistent, or in seroepidemiologic surveys of the prevalence of the infection in certain populations. Babesiosis is usually diagnosed by observing the organisms in infected RBC on Giemsa-stained thin blood films of smeared peripheral blood. Serology may also be useful if the parasitemia is too low to detect or if the infection has cleared naturally or following treatment.


A positive result of an indirect fluorescent antibody test (titer ≥1:64) suggests current or previous infection with Babesia microti. In general, the higher the titer, the more likely it is that the patient has an active infection. Patients with documented infections have usually had titers ranging from 1:320 to 1:2560.

Method Description

This immunofluorescence assay detects antibodies against Babesia microti. The patient's serum is diluted and is placed in microscopic slide wells, which have been coated with B microti infected red blood cells from Syrian hamsters. After incubation, the slides are washed and a fluorescein isothiocyanate conjugate is added to each well. The slides are then read using a fluorescence microscope and significant fluorescent staining of intraerythrocytic organisms constitutes a positive reaction.(Krause PJ, Telford SR III, Ryan R, et al: Diagnosis of babesiosis: Evaluation of a serologic test for the detection of Babesia microti antibody. J Infect Dis. 1994;169:923-926; package insert: Babesia IFA IgG. DiaSorin Molecular; 8/12/2016)

Report Available

Same day/1 to 3 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Heat-inactivated specimen Reject

Method Name

Immunofluorescence Assay (IFA)


If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.