From the Guidelines
Serologic tests for Lyme disease typically become detectable 2-4 weeks after a tick bite or the onset of symptoms. This delay occurs because it takes time for the body to produce measurable antibodies against Borrelia burgdorferi, the bacterium that causes Lyme disease 1. The standard two-tier testing approach first uses an enzyme immunoassay (EIA) or immunofluorescence assay (IFA), followed by a Western blot if the first test is positive or equivocal.
Some key points to consider when interpreting test results include:
- Early testing during the first few days of infection often yields false-negative results because antibody levels haven't yet reached detectable thresholds 1.
- The antibody response begins with IgM antibodies, which typically appear 1-2 weeks after infection and peak at 3-6 weeks.
- IgG antibodies develop more slowly, appearing 2-4 weeks after infection and peaking at 4-6 months 1.
- These antibodies may remain detectable for months or years after the infection has been treated.
It's essential to note that if Lyme disease is suspected based on symptoms and potential tick exposure, treatment should not be delayed while waiting for serologic confirmation. Clinicians must take into account the patient’s history, timeline of symptoms, and pretest probability to accurately order the test and interpret the test result 1.
From the Research
Timeframe for Lyme Disease to Become Detectable
The timeframe for Lyme disease to become detectable through serologic tests after a tick bite or onset of symptoms can vary.
- According to 2, serologic testing should be performed with the complete two-step approach in which a positive or equivocal serology is followed by a more specific Western blot test.
- Samples drawn from patients within four weeks of disease onset are tested by Western blot technique for both immunoglobulin M and immunoglobulin G antibodies; samples drawn more than four weeks after disease onset are tested for immunoglobulin G only.
- In the case report presented in 3, the patient was initially seronegative, but after antibiotic therapy with ceftriaxone and doxycycline, high specific anti-Borrelia antibodies were detected by Western blot and SeraSpot, indicating seroconversion.
Factors Affecting Detectability
Several factors can affect the detectability of Lyme disease, including:
- The stage of the disease at the time of testing, as noted in 2
- The presence of symptoms such as erythema migrans, as mentioned in 4
- The use of antibiotic therapy, which can trigger seroconversion, as seen in 3
- The timing of sample collection, with samples drawn within four weeks of disease onset requiring testing for both immunoglobulin M and immunoglobulin G antibodies, as stated in 2
Clinical Evaluation
Clinical evaluation plays a crucial role in the diagnosis of Lyme disease, especially in patients with symptoms of disseminated Lyme disease, as emphasized in 3.
- A thorough medical history and physical examination are essential in determining the likelihood of Lyme disease.
- Serologic testing should be used in conjunction with clinical evaluation to confirm the diagnosis, as recommended in 2.