What blood tests are performed after a tick bite? - briefly
Serologic testing for Lyme disease (ELISA with confirmatory Western blot) is standard, often accompanied by PCR or serology for other tick‑borne infections such as Babesia, Anaplasma, Ehrlichia, and Rocky Mountain spotted fever.
What blood tests are performed after a tick bite? - in detail
After a tick attachment, clinicians evaluate for infection with pathogens transmitted by the arthropod. Laboratory assessment focuses on agents that cause Lyme disease, anaplasmosis, ehrlichiosis, babesiosis, and other tick‑borne illnesses.
Serologic testing for Borrelia burgdorferi includes an initial enzyme‑linked immunosorbent assay (ELISA) followed by a confirmatory immunoblot. Positive results indicate exposure; timing of the sample matters because antibodies may not appear until 2–4 weeks after the bite.
Polymerase chain reaction (PCR) assays detect DNA of intracellular organisms that may not generate early antibodies. PCR is applied to whole blood or serum for:
- Anaplasma phagocytophilum
- Ehrlichia chaffeensis
- Babesia microti
- Rickettsia species (including R. rickettsii)
A negative PCR does not exclude infection; repeat testing after 5–7 days may increase sensitivity.
Complete blood count (CBC) with differential identifies hematologic abnormalities common in tick‑borne diseases. Typical findings include leukopenia, thrombocytopenia, and anemia, especially in babesiosis. Liver function tests (ALT, AST) and lactate dehydrogenase may be elevated in anaplasmosis and ehrlichiosis. C‑reactive protein (CRP) and erythrocyte sedimentation rate (ESR) provide nonspecific markers of inflammation.
When the clinical picture suggests viral transmission, such as Powassan virus, serology for IgM and IgG antibodies is performed. Neutralization assays confirm positive results.
In practice, the diagnostic algorithm proceeds as follows:
- Obtain CBC, liver enzymes, CRP/ESR.
- Draw blood for Borrelia ELISA; if positive, send immunoblot.
- Collect specimens for PCR targeting Anaplasma, Ehrlichia, Babesia, and Rickettsia.
- If viral exposure is suspected, order specific IgM/IgG serology.
- Repeat serology or PCR after 2 weeks if initial results are negative but symptoms persist.
Interpretation integrates laboratory data with clinical signs, exposure history, and geographic risk. Early detection guides antimicrobial therapy, reduces complications, and informs public‑health reporting.