How should a blood sample be given after a tick bite? - briefly
Collect the specimen by sterile venipuncture into an appropriate tube, label with date, time, and tick‑exposure details, and ship to the laboratory within 24 hours under refrigeration. Order serologic testing for tick‑borne pathogens according to regional protocols.
How should a blood sample be given after a tick bite? - in detail
When a tick bite occurs, the blood specimen must be obtained in a manner that maximizes diagnostic yield for tick‑borne pathogens while preserving sample integrity.
The collection process begins with assessment of the bite site. If the tick remains attached, remove it with fine‑point tweezers, grasping the head close to the skin and pulling upward with steady pressure. Disinfect the surrounding skin using an alcohol swab; allow the area to dry before venipuncture.
Select the appropriate tube based on the intended tests:
- Serum separator tube (SST) for serology of Lyme disease, anaplasmosis, ehrlichiosis, and babesiosis.
- EDTA tube for polymerase chain reaction (PCR) detection of Borrelia, Rickettsia, or Babesia DNA.
- Heparin tube for complete blood count (CBC) and differential if hematologic involvement is suspected.
Perform venipuncture using standard aseptic technique. Insert the needle at a 15‑30° angle into a suitable vein, typically the antecubital fossa. Fill the tube to the marked volume, avoiding over‑filling or under‑filling, which can affect anticoagulant ratios.
After collection, follow these steps:
- Gently invert the tube 5–8 times to mix anticoagulant or clot activator.
- Label each tube with patient identifier, date and time of draw, and an indication of tick exposure.
- Store tubes at the temperature recommended for each assay:
- Serum: allow clotting at room temperature (15‑30 °C) for 30 minutes, then centrifuge; keep serum at 2‑8 °C if testing within 24 hours, otherwise freeze at –20 °C.
- EDTA: keep at 2‑8 °C; transport to the laboratory within 24 hours for PCR.
- Document the bite details: location on the body, date of removal, tick species if identified, and any symptoms such as fever, rash, or arthralgia.
Transport the specimens to the laboratory promptly, using a biohazard‑compliant container. Include a requisition form specifying the tests required: serology, PCR, or culture, and note any recent antimicrobial therapy that could affect results.
Laboratory analysis should encompass:
- Enzyme‑linked immunosorbent assay (ELISA) for IgM/IgG antibodies against Borrelia burgdorferi, followed by Western blot confirmation if positive.
- Multiplex PCR panels targeting DNA of common tick‑borne agents.
- CBC with differential to detect leukopenia, thrombocytopenia, or anemia indicative of systemic infection.
Interpretation of results must consider the timing of the bite. Early infection (≤ 7 days) may yield negative serology; PCR offers higher sensitivity during this window. Seroconversion typically occurs after 2‑4 weeks; repeat testing may be necessary if initial serology is negative but clinical suspicion remains high.
Adherence to this protocol ensures accurate detection of tick‑borne diseases, facilitates timely treatment, and reduces the risk of false‑negative outcomes.