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Test Code BABG Babesia microti IgG Antibodies, Serum

Reporting Name

Babesia microti IgG Ab, S

Useful For

A serologic test can be used as an adjunct in the diagnosis of babesiosis or in seroepidemiologic surveys of the prevalence of the infection in certain populations. Babesiosis is usually diagnosed by observing the organisms in infected RBCs on Giemsa-stained thin blood films of smeared peripheral blood.


Serology may be useful if the parasitemia is too low to detect or if the infection has cleared naturally or following treatment.


Serology may also be useful in the follow-up of documented cases of babesiosis or if chronic or persistent infection is suspected.

Testing Algorithm

See Acute Tick-Borne Disease Testing Algorithm in Special Instructions.

Method Name

Immunofluorescence Assay (IFA)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Specimen Minimum Volume

0.15 mL

Specimen Stability Information

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

Reject Due To


Mild OK; Gross reject


Mild OK; Gross reject





Reference Values


Day(s) and Time(s) Performed

Monday through Friday; 9 a.m.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
BABG Babesia microti IgG Ab, S In Process


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


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 1:2,560.

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 RBCs. In this intraerythrocytic stage it becomes disseminated throughout the reticuloendothelial system. Asexual reproduction occurs in RBCs, and daughter cells (merozoites) are formed which 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.

Method Description

This immunofluorescence assay (IFA) detects antibodies against Babesia microti. The patient's serum is diluted and is placed in microscopic slide wells which have been coated with Babesia microti infected RBCs 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)

Analytic Time

Same day/1 day

Specimen Retention Time

14 days

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 U.S. Food and Drug Administration.


Previous episodes of babesiosis may produce a positive serologic result.


In selected cases, documentation of infection may be attempted by animal inoculation or PCR methods (PBAB / Babesia microti, Molecular Detection, PCR, Blood)         


Performance characteristics have not been established for the following specimen characteristics: