Bburgdorigmindexsercsfacnc
This blood test detects IgM antibodies against Borrelia burgdorferi, the bacteria that causes Lyme disease, helping diagnose early infection after a tick bite.
{"The test looks for IgM antibodies, which are the first antibodies your body makes to fight Lyme disease","A positive result usually means you have an early Lyme disease infection","Results are often confirmed with a second (Western blot) test","The test is most accurate 3-4 weeks after a tick bite","Early detection and treatment lead to better outcomes"}
Key facts at a glance
- LOINC
- 101149-3
- Short code
- LYME-IGM
- Synonyms
- B burgdor IgM Index Ser+CSF-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) for serum; sterile CSF collection tube for cerebrospinal fluid
- Units
- N/A
- Ref low
- 0
- Ref high
- 0.8
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Enzyme-linked immunosorbent assay (ELISA) or Chemiluminescent Immunoassay (CLIA) for qualitative/quantitative detection of IgM antibodies against Borrelia burgdorferi, typically followed by Western blot confirmation
- CPT
- 86617 (Borrelia burgdorferi antibody, IgM); 86618 (Borrelia burgdorferi confirmatory Western blot)
- SNOMED
- 397575002 |Borrelia burgdorferi immunoglobulin M antibody measurement|
- Specimen volume
- 0.5-1 mL serum and/or 0.5-1 mL CSF
- Stability
- Serum stable at room temperature for 8 hours, refrigerated (2-8°C) for 7 days, frozen at -20°C or below for long-term storage. CSF should be processed and stored similarly with analysis ideally within 24-48 hours.
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
What is this test?
The Borrelia burgdorferi IgM Antibody test is a blood test that checks for IgM (immunoglobulin M) antibodies against the bacteria that cause Lyme disease. When a tick carrying Borrelia burgdorferi bites you, your immune system responds by producing IgM antibodies first. These antibodies typically appear within 2-3 weeks of infection and are the earliest sign that your body is fighting the bacteria.
Why might I need this test?
Your healthcare provider may order this test if you have symptoms of early Lyme disease, especially if you have recently been bitten by a tick or spent time in areas where Lyme disease is common. Early symptoms may include a expanding red rash (erythema migrans), fever, headache, fatigue, and muscle aches. The test is most useful when performed 3-4 weeks after potential exposure, as this allows enough time for antibodies to develop.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where technicians look for IgM antibodies against Borrelia burgdorferi. Results are typically reported as an index value, with values above a certain threshold considered positive or borderline.
What do the results mean?
Results are usually reported as an index value. A value below the cutoff is considered negative, meaning no IgM antibodies were detected. A value at or above the cutoff is positive or borderline, suggesting early Lyme disease infection. However, a positive IgM result typically requires confirmation with a Western blot test, which is the standard two-tier testing approach for Lyme disease recommended by the CDC.
Are there any limitations?
This test has some limitations. Early in infection (within the first 2-3 weeks), antibodies may not yet be detectable, potentially causing a false negative result. Conversely, IgM antibodies can sometimes remain positive even after successful treatment, so the test is not used to monitor treatment effectiveness. Additionally, the test may cross-react with antibodies from other similar infections, potentially causing false positives.
Reference range
Negative: <0.80 Index (antibody index); Equivocal: 0.80-1.00 Index; Positive: >1.00 Index. Reference ranges vary by laboratory and assay manufacturer. Results should be interpreted alongside clinical findings and confirmatory Western blot testing.N/A
No special patient preparation required. Fasting is not necessary for this serological test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Does a positive result mean I definitely have Lyme disease?
How long after a tick bite should I wait to get tested?
Can this test tell me if I'm cured after treatment?
What is the difference between IgM and IgG tests?
Is the test painful?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 15, 2026. · Read our editorial policy