- Peripheral smear – diagnosis of babesiosis can be confirmed by microscopic detection of parasites within red blood cells on Giemsa-stained or Wright-stained thin blood smears.
- PCR – more sensitive than a blood smear for detection of Babesia.
- Serology – a single positive Babesia serological test cannot distinguish active from past infection, although a B. microti antibody titer >1:1024 or the presence of IgM antibody suggest recent infection.
Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA): 2020 Guideline on Diagnosis and Management of Babesiosis:
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