What does a blood test show after a tick bite? - briefly
A blood examination after a tick encounter usually checks for antibodies to Borrelia burgdorferi and may include PCR testing for other tick‑borne agents, with a positive result confirming infection. It can also show increased white‑blood‑cell count or inflammatory markers, indicating a systemic response.
What does a blood test show after a tick bite? - in detail
A blood analysis performed after a tick attachment is intended to detect infection with pathogens that the arthropod can transmit. The primary purpose is to identify early signs of Lyme disease, although other tick‑borne illnesses are also screened.
Lyme disease testing
- Enzyme‑linked immunosorbent assay (ELISA) for IgM and IgG antibodies against Borrelia burgdorferi.
- Positive ELISA results are confirmed with a Western blot that distinguishes specific protein bands.
- Seroconversion usually appears 2–4 weeks after the bite; a negative result in the first week does not rule out infection.
Anaplasmosis and Ehrlichiosis
- Polymerase chain reaction (PCR) detects Anaplasma phagocytophilum or Ehrlichia chaffeensis DNA.
- Complete blood count may reveal leukopenia, thrombocytopenia, or elevated liver enzymes, supporting the diagnosis.
Babesiosis
- Blood smear stained with Giemsa or PCR for Babesia microti identifies intra‑erythrocytic parasites.
- Hemoglobin and hematocrit levels may be reduced, indicating hemolysis.
Rocky Mountain spotted fever
- PCR or indirect immunofluorescence assay (IFA) for Rickettsia rickettsii antibodies.
- Elevated liver transaminases and low platelet count are common laboratory clues.
Other considerations
- Serum creatinine and electrolytes assess renal involvement, especially in severe cases.
- C‑reactive protein (CRP) and erythrocyte sedimentation rate (ESR) may be elevated, reflecting systemic inflammation but are nonspecific.
Interpretation requires correlation with the timing of the bite, clinical symptoms (fever, rash, joint pain, headache), and geographic exposure. Early detection through appropriate serologic or molecular assays enables prompt antimicrobial therapy, reducing the risk of severe complications.