How many days after a tick bite should blood be taken to test for borreliosis? - briefly
Blood should be drawn no sooner than 14–21 days after the bite, with optimal antibody detection at around 28 days.
How many days after a tick bite should blood be taken to test for borreliosis? - in detail
The optimal interval for drawing blood to detect Lyme disease after a tick attachment is not immediate. Antibody production usually begins 2 – 3 weeks post‑exposure, making serologic assays reliable only after this period. Testing before day 14 often yields false‑negative results because the immune response has not yet generated detectable IgM or IgG levels.
Guidelines recommend the following schedule:
- Initial sample: 14–21 days after the bite. At this point, an enzyme‑linked immunosorbent assay (ELISA) followed by a Western blot can identify early IgM antibodies.
- If the first test is negative and symptoms persist: repeat the draw at 28–42 days. IgG antibodies typically appear during this window, improving diagnostic sensitivity.
- For late manifestations (e.g., arthritis, neurological involvement): a sample taken ≥ 60 days post‑exposure is advisable, as IgG titers are higher and more stable.
Special considerations:
- Presence of the characteristic rash (erythema migrans) permits immediate treatment without waiting for serology.
- Polymerase chain reaction (PCR) on peripheral blood is rarely positive; it is reserved for specific cases such as early disseminated disease or when joint fluid is examined.
- In suspected neuroborreliosis, cerebrospinal fluid analysis is performed after at least 4 weeks, because intrathecal antibody production lags behind serum responses.
In practice, clinicians should collect the first specimen no earlier than two weeks after the tick bite, reassess clinical signs, and schedule a follow‑up test if the initial result is inconclusive. This approach balances the need for timely diagnosis with the biology of antibody development.