Lyme Disease Antibody (Screen)
A first-step blood test for antibodies to the bacteria that cause Lyme disease. A positive or equivocal result is followed by a second test.
AI-verified against cited sources. Awaiting expert reviewAlso called Lyme Ab, Bb Ab, Lyme EIALOINC 83081-0
What it is
Lyme disease is spread by tick bites. This test looks for antibodies, which are proteins your immune system makes against the Lyme bacteria (Borrelia burgdorferi). It is the first step in a two-step approach recommended by the CDC. If it is negative, no more testing is usually needed. If it is positive or equivocal, the lab runs a second test on the same blood sample, either a Western blot or another antibody test (EIA).
Why it matters
A test result alone cannot diagnose Lyme disease. Your clinician looks at your symptoms, whether you may have been exposed to ticks, and your test results together. The two-step approach exists because the first test casts a wide net and can pick up antibodies made against other germs. A positive result on both steps, together with symptoms, fits with Lyme disease.
If it’s low
A negative result means no Lyme antibodies were found. After the first several weeks of illness, a negative result makes Lyme disease less likely. But the body takes a few weeks to make antibodies, so a test in the first weeks of illness can be negative even when infected. This is called a false negative.
Common causes
- You do not have Lyme disease
- The blood was drawn early, before your body made enough antibodies (CDC: the first 4 to 6 weeks)
What can help
- If you were tested within a few weeks of symptoms starting, ask whether to repeat the test later
- Tell your clinician if new symptoms appear
If it’s high
A positive or equivocal first test means antibodies that may react with the Lyme bacteria were found. This is not a diagnosis. The lab runs a second test on the same sample. Antibodies can stay in the blood for months to years after an infection, so a positive result does not always mean Lyme disease is causing your symptoms today.
Common causes
- Antibodies left over from a past Lyme infection, even one that was treated or cleared long ago
- Cross-reacting antibodies from other conditions, including relapsing fever, syphilis, rheumatoid arthritis, Epstein-Barr virus infection and some autoimmune diseases
- A current Lyme disease infection
What can help
- Ask whether the second-step test is run on the same blood sample
- Tell your clinician when your symptoms started and about any tick bites, rashes or travel to areas where Lyme disease is common
- Ask how your symptoms, tick exposure and test results fit together
What can affect your result
- How long you have been infected: antibodies take weeks to appear
- A past Lyme infection: antibodies can stay positive for months to years
- Other infections and autoimmune conditions can cause false positives
- The test design: labs use different antigens (for example whole-cell or C6 peptide) and different cutoffs
- Antibody tests can be falsely negative in the first 4 to 6 weeks after infection (CDC).
- False positives can occur with other conditions, including relapsing fever, syphilis, rheumatoid arthritis and Epstein-Barr virus infection (CDC), and with some autoimmune diseases (MedlinePlus).
- IgM results should be disregarded if you have been ill for more than 30 days (CDC).
Antibodies take a few weeks to appear after infection and can stay detectable for months to years, even after successful treatment. The result cannot show that an infection has been cured.
When to talk to a clinician
Contact a clinician promptly if, after a possible tick exposure, you have a rash that keeps spreading, new drooping of one side of the face, severe headache with a stiff neck, a swollen and painful joint, or a change in your heart rate or rhythm. Do not wait for test results if symptoms are severe.
Questions you could ask
- Does the timing of my symptoms change how to read this test?
- Which second-step test was run on my sample, and what did it show?
- Could this result be from an old infection or another condition?
- Do my symptoms and tick exposure fit with Lyme disease?
- Should I repeat the test later, since I was tested soon after my symptoms began?
Questions people ask
Why is a second test needed if the first one is positive?
The first test is designed to catch as many true infections as possible, so it also picks up some antibodies made against other germs. The second test makes the answer more specific. The CDC recommends running it on the same blood sample.
Can I be tested right after a tick bite?
A test right after a bite can miss an infection. The CDC says antibody tests may be falsely negative during the first 4 to 6 weeks. Your clinician can tell you whether testing makes sense and when.
Does a positive result mean I have Lyme disease right now?
Not necessarily. Antibodies can last for months or even years after an infection that was treated or cleared, so your clinician reads the result together with your symptoms, your tick exposure and the second-step test.
Show the science and sources
For clinicians and researchers
First tier of the CDC two-tier algorithm. Standard two-tier testing (STTT) pairs an EIA with an IgM/IgG Western blot. Modified two-tier testing (MTTT) uses a second EIA in place of the blot, and FDA cleared such assays in July 2019 (Mead et al., MMWR 2019). CDC: if the first step is negative, no further testing is recommended. If it is positive or equivocal, the second step is run on the same sample, and an overall positive needs both steps to be positive (or equivocal for some tests). Mayo Clinic Laboratories' modified two-tier screen (SLYME) is an ELISA with the reference value 'Negative' for all ages, and positive or equivocal results reflex to a whole-cell sonicate IgM/IgG EIA (TLYME). Mayo notes the test should not be used to screen the general population. CDC: serologic assays may be falsely negative during the first 4 to 6 weeks after infection, positive IgM results should be disregarded if the patient has been ill for more than 30 days, and antibody titers can remain elevated for months to years and cannot determine cure. Cross-reactivity is reported with relapsing fever, syphilis, rheumatoid arthritis and EBV infection. Index values and cutoffs are assay-specific.
LOINC 83081-0 (primary), 11006-4, 46248-1, 57916-9, 38173-1. Specimen: serum.
Sources
- Clinical Testing and Diagnosis for Lyme Disease, CDC
- Updated CDC Recommendation for Serologic Diagnosis of Lyme Disease, MMWR Morbidity and Mortality Weekly Report (CDC) (2019)
- Lyme Antibody Modified 2-Tier with Reflex, Serum (test SLYME), Mayo Clinic Laboratories (Extended Catalog)
- Lyme Disease Tests, MedlinePlus (NIH)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.