How to test for borreliosis after a tick bite? - briefly
Initial assessment uses a two‑tier serology: an ELISA screening, confirmed by a Western blot if positive. For early disease, PCR of blood or skin biopsy may be added, and a physician may also evaluate the erythema migrans rash clinically.
How to test for borreliosis after a tick bite? - in detail
Testing for Lyme disease after a tick exposure requires a systematic approach that integrates clinical assessment, timing of specimen collection, and appropriate laboratory methods.
The first step involves evaluating the bite site and the presence of erythema migrans or other suggestive signs. If the tick was attached for more than 24 hours, the probability of infection increases, prompting laboratory investigation even in the absence of rash.
Serological testing remains the primary diagnostic tool. The recommended algorithm includes:
- An initial enzyme‑linked immunosorbent assay (ELISA) to detect IgM and IgG antibodies against Borrelia burgdorferi antigens.
- A confirmatory Western blot performed only when the ELISA result is positive or equivocal. Interpretation follows established criteria: IgM positivity requires at least two of three specific bands, whereas IgG positivity requires five of ten bands.
Timing of blood sampling influences sensitivity. Antibody production typically becomes detectable 2–4 weeks after the bite; therefore, specimens collected earlier may yield false‑negative results. In cases of early localized disease with a characteristic rash, treatment may commence without serology.
Molecular methods supplement serology in specific circumstances. Polymerase chain reaction (PCR) testing of skin biopsy from erythema migrans, synovial fluid, or cerebrospinal fluid (CSF) can identify Borrelia DNA, offering higher specificity for disseminated infection. PCR sensitivity varies by specimen type and disease stage.
CSF analysis is indicated when neurological involvement is suspected. Routine examination includes cell count, protein concentration, and intrathecal antibody production measured by the antibody index. A positive intrathecal IgG synthesis confirms neuroborreliosis.
Culture of Borrelia from skin or blood is rarely performed because of low yield and prolonged incubation periods; it is reserved for research settings.
Interpretation of results must consider pre‑test probability, disease stage, and potential cross‑reactivity with other spirochetes. Negative serology in early disease does not exclude infection; repeat testing after 4 weeks is advisable if symptoms persist.
Following laboratory confirmation, appropriate antibiotic therapy is initiated according to established guidelines, and patients are monitored for clinical response. Regular follow‑up ensures resolution of symptoms and identifies any late manifestations that may require additional evaluation.