Initial screening or confirmatory testing 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
Real-Time Polymerase Chain Reaction (PCR)/DNA Probe Hybridization
Babesia microti
Babesiosis, PCR
PCR (Polymerase Chain Reaction)
PCR, Babesia divergens
PCR, Babesia duncani
PCR, Babesia microti
PCR, Babesia MO-1
Whole Blood EDTA
This is a qualitative assay, and the results are reported either as negative or positive for targeted Babesia species DNA.
Container/Tube: Lavender top (EDTA)
Specimen Volume: 1 mL
Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
0.5 mL
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood EDTA | Refrigerated | 7 days |
Initial screening or confirmatory testing 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
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 Babesia duncani human infection have also been reported along Pacific Coast states from Washington to northern California, and Babesia divergens/B divergens-like strains have been detected in humans in Missouri (MO-1 strain), Kentucky, and Washington. In Europe, B divergens and Babesia 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 polymerase chain reaction 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.
Negative
Reference values apply to all ages.
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 (polymerase chain reaction: 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.
While this assay is designed to detect symptomatic infection with Babesia microti, Babesia duncani, and Babesia divergens/MO-1, it may detect low-grade asymptomatic parasitemia in individuals in babesiosis-endemic areas. Thus, it should only be used for testing patients with a clinical history and symptoms consistent with babesiosis.
Inhibitory substances may cause false-negative results.
Inadequate specimen collection or improper storage may invalidate test results.
The following validation data supports the use of this assay for clinical testing.
Accuracy/Diagnostic Sensitivity and Specificity:
Ninety-six whole blood specimens were tested by this real-time polymerase chain reaction (PCR) assay and another real-time PCR assay. Concordance was 99%.
Analytical Sensitivity/Limit of Detection:
The limit of detection established using whole organism spiked into specimen matrix (whole blood) is as follows:
-Babesia microti, ATCC PRA 99-2670 target copies/mL
-Babesia duncani ATCC PRA 302-1540 target copies/mL
-Babesia MO-1 positive patient DNA-10,700 target copies/mL
-Babesia divergens positive patient DNA-5270 target copies/mL
Serial 10-fold dilutions of microscopy-positive specimens were also tested in a blinded fashion using conventional thick and thin blood films and the Mayo Clinic Babesia species PCR test. The PCR test was able to consistently detect two 10-fold dilutions lower than using microscopy.
Analytical Specificity:
No cross-reactivity was noted using a panel of 34 bacteria, viruses, parasites, and fungi were detected by the Babesia species PCR.
Precision:
Interassay and intra-assay precision was 100% precision.
Reference Range:
The reference range is negative. This was confirmed by testing 93 blood specimens from asymptomatic individuals for the presence of Babesia species by the Babesia species PCR assay. All 93 specimens were negative.
Reportable Range:
This test is a qualitative assay, and results are reported as positive or negative for Babesia species (B microti, B duncani, B divergens, and Babesia MO-1).
1. Anderson JF, Mintz ED, Gadbaw JJ, et al: Babesia microti, human babesiosis and Borrelia burgdorferi in Connecticut. J Clin Microbiol. 1991 Dec;29(12):2779-2783
2. Herwaldt BL, de Bruyn G, Pieniazek NJ, et al: Babesia divergens-like infection, Washington State. Emerg Infect Dis. 2004 Apr;10(4):622-629
3. Herwaldt B, Persing DH, Precigout EA, et al: A fatal case of babesiosis in Missouri: identification of another piroplasm that infects humans. Ann Intern Med. 1996 Apr 1;124(7):643-650
4. Persing DH, Herwaldt BL, Glaser C, et al: Infection with a Babesia-like organism in northern California. N Engl J Med. 1995 Feb 2;332(5):298-303
5. Quick RE, Herwaldt BL, Thomford JW, et al: Babesiosis in Washington State: a new species of Babesia? Ann Intern Med. 1993 Aug 15;119(4):284-290
6. Vannier E, Krause PJ: Human Babesiosis. N Engl J Med. 2012 Jun 21;366(25):2397-2407
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 polymerase chain reaction (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 that 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 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 Jun 1;64(11):1622-165)
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
87798 x2
87469
87999 (if appropriate for government payers)
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| BABPB | Babesia species PCR, B | 88461-9 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 618317 | Babesia microti | 88452-8 |
| 618318 | Babesia duncani | 88451-0 |
| 618319 | Babesia divergens/MO-1 | 88450-2 |