How long after a tick bite should tests for encephalitis be performed? - briefly
Serologic testing for tick‑borne encephalitis is typically done 7–14 days after the onset of neurological symptoms, which generally develop 1–2 weeks post‑bite. Testing before this period often produces false‑negative results.
How long after a tick bite should tests for encephalitis be performed? - in detail
Tick‑borne encephalitis (TBE) usually appears 7–14 days after the bite, with occasional cases up to 28 days. Testing strategies depend on whether the patient is symptomatic or asymptomatic.
Symptomatic individuals
- At the first neurological sign (fever, headache, meningitis, or encephalitis) draw blood for TBE‑specific IgM and IgG ELISA.
- Perform cerebrospinal‑fluid analysis simultaneously; look for pleocytosis, elevated protein, and TBE‑IgM in CSF.
- If the initial serology is negative but clinical suspicion remains high, repeat IgM/IgG testing after 5–7 days, because antibodies may not be detectable during the very early phase.
- Real‑time PCR on blood or CSF is useful within the first week of symptom onset, before antibodies appear.
Asymptomatic persons with known exposure
- Obtain a baseline serum sample as soon as possible after the bite (ideally within 48 h).
- Schedule a follow‑up sample 2–3 weeks later to detect seroconversion.
- If the first sample is already positive for IgM, a second sample 2 weeks later confirms rising IgG titers, indicating recent infection.
Key timing points
- Day 0–6: PCR may identify viral RNA; serology usually negative.
- Day 7–14: IgM becomes reliably detectable; IgG may appear later.
- Day 14–28: IgG levels rise; repeat serology confirms seroconversion.
Testing earlier than day 5 rarely yields positive serology, while testing after day 28 may miss the acute phase but still documents recent infection through IgG. Clinical decision‑making should align testing with the expected incubation window and symptom onset to maximize diagnostic yield.