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Test Code MISC2MAYOLBAB Babesia species, Molecular Detection, PCR, Blood

Useful For

An initial screening or confirmatory testing method for suspected babesiosis during the acute febrile stage of infection in patients from endemic areas, especially when Giemsa-stained peripheral blood smears do not reveal any organisms or the organism morphology is inconclusive.

Reporting Name

Babesia species, PCR, B

Specimen Type

Whole Blood EDTA


Ordering Guidance


This is a qualitative assay and the results are reported either as negative or positive for targeted Babesia species DNA.



Specimen Required


Container/Tube: Lavender top (EDTA)

Specimen Volume: 1 mL


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood EDTA Refrigerated 7 days

Reject Due To

Hemolysis Mild OK; Gross OK
Lipemia Mild OK; Gross reject
Icterus NA
Other Green-top (heparin) tube

Clinical Information

Babesiosis is a tick-transmitted zoonosis caused by intraerythrocytic protozoa in the genus Babesia. Babesia microti is responsible for the vast majority of human cases in the United States, with most cases occurring along the Northeast Coast and the upper Midwestern states. A small number of cases of B duncani human infection have also been reported along Pacific Coast states from Washington to northern California, and B divergens/B divergens-like strains have been detected in humans in Missouri (MO-1 strain), Kentucky, and Washington. In Europe, B divergens and B venatorum are the primary causes of human babesiosis.

 

Humans most commonly acquire infection through the bite of an infected tick. The most common tick vectors in the United States are Ixodes scapularis and Ixodes pacificus, while Ixodes ricinus and other ticks transmit the parasite in Europe and Asia. Less commonly, babesiosis may be acquired through blood transfusion and across the placenta from the mother to the fetus.

 

Most patients with babesiosis are asymptomatic or have only a self-limited mild flu-like illness, but some develop a severe illness that may result in death. Patient symptoms may include fever, chills, extreme fatigue, and severe anemia. The most severe cases occur in asplenic individuals and those over 50 years of age. Rare cases of chronic parasitemia, usually in immunocompromised patients, have been described.

 

Babesiosis is conventionally diagnosed through microscopic examination of Giemsa-stained thick and thin peripheral blood films looking for characteristic intraerythrocytic Babesia parasites. This method is relatively rapid, widely available, and capable of detecting (but not differentiating) human-infective Babesia species. It is also necessary for calculating the percentage of parasitemia which is used to predict prognosis, guide patient management, and monitor response to treatment. However, microscopic examination requires skilled microscopists and may be challenging in the setting of low parasitemia or prior drug therapy. Also, Babesia species may closely resemble those of Plasmodium falciparum.

 

The Mayo Clinic real-time PCR assay provides a rapid and more sensitive alternative to blood film examination for detection and differentiation of B microti, B duncani, and B divergens/B divergens-like parasites. It does not cross-react with malaria parasites.

Reference Values

Negative

Interpretation

A positive result indicates the presence of Babesia species DNA and is consistent with active or recent infection. While positive results are highly specific indicators of disease, they should be correlated with blood smear microscopy, serological results and clinical findings.

 

A negative result indicates absence of detectable DNA from Babesia species in the specimen, but does not always rule out ongoing babesiosis in a seropositive person, since the parasitemia may be present at a very low level or may be sporadic.

 

Other tests to consider in the evaluation of a patient presenting with an acute febrile illness following tick exposure include serologic tests for Lyme disease (Borrelia burgdorferi), and molecular detection (PCR) for ehrlichiosis/anaplasmosis. For patients who are past the acute stage of infection, serologic tests for these organisms should be ordered prior to PCR testing.

Method Description

Nucleic acid is extracted from EDTA whole blood using the automated MagNA Pure bead-based system (Roche Molecular Systems). The extract is then transferred to individual self-contained capillary cuvettes for amplification. The LightCycler is an automated instrument that amplifies and monitors the development of target nucleic acid (amplicon) after each cycle of PCR.

 

The DNA target for PCR assay is a gene encoding the nuclear small subunit ribosomal RNA (SS-rDNA). This assay consists of 2 forward primers, 1 reverse primer, and 2 probes, which are specific for the Babesia species target DNA. The specific base pair DNA target sequence is first amplified by PCR using the target-specific primers. Amplicon is then detected during melting curve analysis using fluorescence resonance energy transfer (FRET) probes, which utilizes one hybridization probe with a donor fluorophore, fluorescein, at the 3' end and a second hybridization probe with an acceptor fluorophore, LC-Red 640, at the 5' end. Fluorescence is produced when the 2 probes anneal to the target sequence in close proximity to one another. The LC-Red 640 then emits a measurable and quantifiable light signal at a specific wavelength.(Burgess MJ, Rosenbaum ER, Pritt BS, et al. Possible Transfusion-Transmitted Babesia divergens-like/MO-1 in an Arkansas Patient. Clin Infect Dis 2017; Supplemental Data)

Day(s) Performed

Monday through Saturday; Varies

Report Available

Same day/1 day - 4 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed, and its performance characteristics 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

87798 x 3

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LBAB Babesia species, PCR, B 88461-9

 

Result ID Test Result Name Result LOINC Value
36114 Babesia microti 88452-8
36115 Babesia duncani 88451-0
36116 Babesia divergens/MO-1 88450-2

Method Name

Real-Time Polymerase Chain Reaction (PCR)/DNA Probe Hybridization

Secondary ID

62847

Forms

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