What is the role of a polymerase chain reaction (PCR) assay in the workup of babesiosis?

Updated: Apr 01, 2021
  • Author: Rachel E Strength, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Polymerase chain reaction (PCR)–based diagnostic assays have increased the detection rate of very low-level parasitemia. PCR is now one of the recommended laboratory tests for diagnosis for babesiosis, the other test being peripheral blood smear evaluation. [3]  Persistence of antibody titers for B. microti has been shown to correlate with the detection of babesial DNA by PCR. [39]  The detection of babesial DNA by PCR has been reported for as long as 27 months after untreated infection. [40]

Compared with peripheral smear evaluation and hamster inoculation, PCR testing is more sensitive and equally specific. It may be useful in monitoring the infection, though it cannot differentiate between acute or active forms of babesiosis and chronic forms of the disease. In particular, PCR testing may be used to help diagnose recrudescent Babesia infection in patients who have previously had babesiosis or those whose treatment is of questionable effectiveness.

Immunocompromised patients should be monitored for Babesia parasitemia with peripheral blood smears even after they become asymptomatic.  If an immunocompromised patient continues to have symptoms, but their blood smears have become negative, consider PCR testing. [3]

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