Table 1.

Diagnosis of Lyme Disease, Human Granulocytic Anaplasmosis and Babesiosis

Disease	Manifestation	Diagnostic Approach	Additional Considerations
Lyme disease	Erythema migrans	Visual inspection of skin lesion9	Serology not recommended because seropositivity <40% on acute phase serum sample8.
	Extracutaneous manifestations including but not limited to: facial nerve palsy, meningitis, radiculopathy, myopericarditis, arthritis	Serologic testing132: EIA followed by western blot (IgM and IgG western blots if ≤4 weeks of symptoms; IgG western blot only if >4 weeks or for Lyme arthritis)a	In Lyme meningitis, consider testing CSF for intrathecal borrelial antibody production and for borrelial DNA5; in Lyme arthritis, consider testing synovial fluid for borrelial DNA43.
HGA	Fever, typically with leukopenia, thrombocytopenia, and/or increased transaminases	Blood smear87; buffy coat smear; PCR for A. phagocytophilum DNA.	Serology not routinely recommended except for retrospective diagnosis in treated patients. Seropositivity < 50% on acute phase serum sample and seropositivity alone does not establish the presence of active infection55. Failure to defervesce within 48 hours of initiation of doxycycline is evidence against the diagnosis2.
Babesiosis	Fever, typically with anemia, thrombocytopenia, elevated lactate dehydrogenase, hyperbilirubinemia and/or increased transaminases	Blood smear preferred56; PCR for B. microti DNA is an alternative.	Serologic testing for IgM/IgG antibodies by indirect immunofluorescent assay can be performed, but seropositivity per se does not indicate active infection56.

^asee text for potential alternative testing strategies under consideration