Borrelia burgdorferi IgG, IgM Antibodies by Western Blot
The B. burgdorferi IgG and IgM Western Blot detects band-specific serum antibodies to Borrelia burgdorferi antigens by molecular weight, serving as the confirmatory tier-two assay in the two-tier Lyme disease testing algorithm following a positive or equivocal ELISA screen. IgM Western Blot is the appropriate early marker within the first four weeks of symptom onset; IgG Western Blot confirms an established immune response in late disseminated and chronic presentations. Immunosciences Lab, Inc. provides expanded band reporting beyond the standard CDC 10-band IgG and 3-band IgM panels.
2
Biomarkers
Blood (serum)
Sample
5–10 business days
Turnaround
No
Fasting
What is the Lyme Western Blot (IgG/IgM) test?
The B. burgdorferi IgG, IgM by Western Blot test detects serum antibodies to specific Borrelia burgdorferi protein antigens by molecular weight, providing band-specific confirmatory serological evidence of immune response to the causative organism of Lyme disease. It is ordered as the second tier in the standard two-tier Lyme testing algorithm — following a positive or equivocal tier-one ELISA or EIA — to confirm the specificity of serological reactivity and differentiate true positive from cross-reactive results. Immunosciences Lab, Inc. is a specialty immunology laboratory with an expanded Lyme serology repertoire that may include reporting beyond the standard CDC 10-band IgG and 3-band IgM panels, providing practitioners with a more granular band-level picture than standard reference laboratory Lyme Western Blots. The clinical positioning of this test requires careful framing. Western Blot for Lyme disease is a confirmatory — not screening — assay. It should not be ordered without a prior positive or equivocal tier-one ELISA result in the standard two-tier architecture, as isolated Western Blot ordering in low-prevalence populations or low pre-test probability presentations significantly increases the rate of false-positive interpretation. However, in clinical practice, two-tier testing has known limitations: ELISA sensitivity is reduced in early infection before seroconversion, and practitioners with clinical presentations strongly suggestive of Lyme disease in endemic areas may order a Western Blot directly when the clinical context justifies bypassing the two-tier gate. Results from this assay must always be interpreted in the context of geographic exposure, clinical presentation, symptom timeline, and prior antibiotic treatment — serology alone does not diagnose or exclude active Lyme disease, and neither a positive nor a negative result should be used in isolation.
What does the Lyme Western Blot (IgG/IgM) test measure?
IgG class antibodies to B. burgdorferi develop 4–6 weeks following infection as the humoral immune response matures beyond the initial IgM phase. In Western Blot format, denatured B. burgdorferi proteins are separated by molecular weight on polyacrylamide gel, transferred to nitrocellulose membrane, and probed with patient serum — reactive bands appear at positions corresponding to the molecular weights of the antigenic proteins to which the patient has generated antibodies. Persistence of IgG reactivity is typical following treated and untreated Lyme disease and does not independently indicate ongoing active infection.
IgG Western Blot is the confirmatory tier-two assay in the standard two-tier testing algorithm for Lyme disease. It is used following a positive or equivocal ELISA/EIA screening result to confirm the specificity of the serological response. The specific band pattern — particularly the presence of highly specific bands such as 23 kDa (OspC), 39 kDa (BmpA), and 93 kDa — informs the clinician about the immunological stage of infection. IgG positivity indicates a mature, established immune response and is the appropriate marker for evaluation of late disseminated and chronic Lyme disease presentations.
IgM antibodies to B. burgdorferi are the first immunoglobulin class generated following infection, typically appearing within 2–4 weeks of tick exposure and peaking at 3–6 weeks. The IgM response is directed primarily against the 23 kDa OspC surface protein and the 41 kDa flagellin protein. IgM levels typically decline after the acute phase but may persist for months or years in some individuals, which is a critical interpretive consideration — persistent IgM reactivity alone does not indicate ongoing or reactivated infection.
IgM Western Blot is the appropriate confirmatory marker for early Lyme disease (within the first 4 weeks of symptom onset), where IgG seroconversion may not yet have occurred. A positive IgM Western Blot following a positive or equivocal tier-one ELISA, in a patient presenting within 4 weeks of suspected tick exposure with compatible clinical features (erythema migrans, flu-like illness), supports a diagnosis of early Lyme disease. IgM Western Blot reactivity in patients with symptoms persisting beyond 4–6 weeks should be interpreted cautiously — isolated persistent IgM positivity without concurrent IgG in late presentations is more likely to represent non-specific reactivity, prior resolved infection, or laboratory cross-reactivity than ongoing active infection.
Why is the Lyme Western Blot (IgG/IgM) test ordered?
- Confirmation of positive or equivocal tier-one Lyme ELISA or EIA result — the primary clinical indication per CDC two-tier algorithm for patients with a reactive screen and compatible clinical presentation or tick exposure history
- Early Lyme disease evaluation within the first 4 weeks of symptom onset — IgM Western Blot is the appropriate tier-two confirmatory marker when IgG seroconversion may not yet have occurred, particularly when erythema migrans or early flu-like illness follows a known tick bite in an endemic area
- Late disseminated Lyme disease evaluation — IgG Western Blot for patients presenting with Lyme arthritis, neurological features (facial nerve palsy, meningitis, radiculopathy), or cardiac involvement (atrioventricular block) where a mature IgG response is expected
- Post-treatment evaluation in patients with persistent symptoms following standard antibiotic therapy — interpretation requires awareness that antibody positivity may persist for years after successful treatment and does not confirm ongoing active infection
- Integrative and functional medicine practitioners working up patients with chronic multi-system complaints in Lyme-endemic areas where prior standard two-tier testing has been negative or equivocal but clinical suspicion remains — Immunosciences Lab, Inc.'s expanded band reporting may provide additional clinical information beyond standard laboratory panels # REVIEWER FLAG: This application diverges from mainstream infectious disease guidelines, which do not recommend alternative Lyme testing following standard two-tier negative results. Reviewer to assess appropriate framing for the platform's practitioner audience.
- Practitioners seeking expanded band-level reporting beyond the standard CDC panel for patients in whom atypical band patterns or borderline standard results require further clinical characterisation
- Monitoring serological response in patients undergoing Lyme disease treatment within clinical research or integrative practice protocols where serial band-level data is required
- Differential diagnosis of suspected tick-borne co-infection workup — as part of a broader tick-borne illness panel alongside Anaplasma, Ehrlichia, Babesia, and Bartonella serology in patients with complex multi-system presentations in endemic areas
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Phlebotomy at Immunosciences Lab, Inc. designated draw site or practitioner office collection
Turnaround
5–10 business days
Collection notes
Standard venipuncture into a serum separator tube (SST / gold top). No fasting or special preparation required. Practitioners should document symptom onset date, tick exposure history (date and location if known), geographic residence and recent travel to Lyme-endemic areas, prior antibiotic treatment history for Lyme disease, and current immunosuppressive medications on the requisition form — all are critical for accurate result interpretation. Specimen should be processed and shipped according to Immunosciences Lab, Inc. cold-chain guidelines. # REVIEWER FLAG: Confirm exact tube type, minimum volume, shipping temperature, and processing requirements with Immunosciences Lab, Inc. specimen handling documentation before publication.
Specimen requirements
Minimum 1.0 mL serum. Centrifuge and separate serum within 2 hours of collection. Ship at 2–8°C for delivery within 48 hours; freeze at −20°C if longer storage or transport is required. # REVIEWER FLAG: Confirm minimum volume and stability data for both IgG and IgM Western Blot assays with Immunosciences Lab, Inc.
What can affect Lyme Western Blot (IgG/IgM) results?
Spirochaetes share conserved antigenic proteins — particularly flagellin (41 kDa) — that can generate cross-reactive antibodies, producing false-positive or non-specific band reactivity on B. burgdorferi Western Blot. Syphilis (Treponema pallidum) seropositivity is the most clinically important cross-reactant and should be considered when isolated 41 kDa reactivity is present. Clinical history and concurrent syphilis serology should be assessed when cross-reactivity is suspected.
Polyclonal B-cell activation during active EBV and CMV infection and in systemic autoimmune diseases can produce non-specific antibody bands on B. burgdorferi Western Blot, most commonly involving the 41 kDa flagellin and 66 kDa heat shock protein bands. These non-specific patterns rarely meet full CDC positivity criteria but may generate equivocal or low-level reactive reports that require clinical context for interpretation.
Successful antibiotic treatment does not reliably or rapidly clear Lyme seropositivity. IgG Western Blot bands may remain reactive for years to decades following treated infection — persistent band positivity after treatment does not confirm ongoing active disease and must not be used as the sole basis for continued antibiotic therapy. IgM reactivity can also persist. Practitioners must document prior treatment history relative to specimen collection.
Antibody seroconversion requires 2–4 weeks for IgM and 4–6 weeks for IgG following B. burgdorferi infection. Specimens collected within the first 2–3 weeks of acute infection may return seronegative or indeterminate results despite active infection. When strong clinical suspicion exists in this window — particularly with erythema migrans — clinical diagnosis and empirical treatment should not be withheld pending confirmatory serology.
Pharmacological immunosuppression — corticosteroids, DMARDs, biologics, or chemotherapy — can suppress B. burgdorferi-specific antibody production below the detection threshold in both ELISA and Western Blot formats, producing false-negative results in patients with genuine exposure or active infection. Clinical and exposure history is essential when interpreting seronegative results in immunocompromised patients.
The OspA-based LYMErix vaccine, marketed in the USA from 1998 to 2002, induced antibody reactivity at the 31 kDa (OspA) Western Blot band. This band is excluded from CDC IgG positivity criteria specifically to prevent vaccine-induced false positives. Practitioners should document vaccination history — including the now-discontinued LYMErix — when interpreting band patterns that include 31 kDa reactivity. # REVIEWER FLAG: A next-generation OspA-based Lyme vaccine (VLA15/Valneva) is in late-stage development as of 2025; confirm current approval status and update guidance accordingly if approved.
Significant haemolysis or severe lipemia can interfere with nitrocellulose membrane binding and band detection in Western Blot format, potentially affecting band intensity interpretation. Visibly compromised specimens should be rejected and recollected. # REVIEWER FLAG: Confirm Immunosciences Lab, Inc. specimen rejection criteria for this assay.
What do Lyme Western Blot (IgG/IgM) results mean?
Elevated
A positive IgG Western Blot (≥5 of 10 CDC bands reactive) following a positive tier-one ELISA confirms serological evidence of B. burgdorferi immune response consistent with past or present Lyme disease in the context of compatible clinical presentation and exposure history. Positive IgG in a patient with acute short-duration symptoms is unusual and should prompt reassessment of the symptom timeline — IgG seroconversion requires 4–6 weeks and its presence suggests a longer or recurrent exposure history. A positive IgM Western Blot (≥2 of 3 CDC bands) in a patient within 4 weeks of symptom onset with a positive tier-one ELISA supports early Lyme disease diagnosis in the context of endemic area exposure and compatible clinical features. Expanded Immunosciences Lab, Inc. band reporting may identify additional reactive bands beyond standard CDC criteria — these should be interpreted with clinical caution, as their significance for treatment decision-making is not standardised in mainstream guidelines.
Normal
A fully negative two-tier Lyme test (negative tier-one ELISA or negative confirmatory Western Blot following a positive screen) makes active Lyme disease significantly less likely in immunocompetent patients with symptoms beyond 4–6 weeks of onset. Alternative diagnoses — viral illness, post-infectious syndrome, fibromyalgia, inflammatory arthritis — should be pursued when the two-tier result is negative and symptoms persist. Serology cannot definitively exclude very early infection within the first 2–3 weeks; clinical assessment and empirical treatment in high-suspicion early presentations takes precedence over a negative serological result.
Reduced
A negative Western Blot following a positive or equivocal tier-one ELISA indicates that the initial screen reactivity is likely non-specific and does not represent true B. burgdorferi antibody. In patients with symptoms of less than 4 weeks' duration, a seronegative result does not exclude early Lyme disease, as seroconversion may not yet have occurred — clinical diagnosis and treatment should be based on clinical presentation and exposure history in this window, not serology alone. In patients with longer-duration symptoms and a seronegative two-tier result, Lyme disease is unlikely but not fully excluded in strongly endemic areas; re-testing in 2–4 weeks may be warranted if early acute seronegative presentation is suspected.
Note: The most significant interpretive caveat is that Western Blot seropositivity — whether IgG or IgM — confirms prior immune exposure to B. burgdorferi but cannot establish that B. burgdorferi is the current cause of a patient's presenting symptoms. Antibody positivity can persist for years to decades after successfully treated infection. A positive Lyme Western Blot in a patient with non-specific symptoms (fatigue, cognitive difficulties, diffuse pain) in the absence of objective clinical signs of Lyme disease — or in a patient without plausible endemic area tick exposure — requires particular caution. Isolated persistent IgM positivity without concurrent IgG in patients with long-duration symptoms is more likely to reflect non-specific reactivity or prior resolved infection than ongoing active disease and should not independently drive treatment decisions. The expanded band reporting provided by Immunosciences Lab, Inc. beyond the standard CDC panel should be interpreted with awareness that non-standard bands have not been validated in the same evidence framework as CDC-approved criteria. PCR or culture from tissue or synovial fluid is the appropriate confirmatory test when active infection requires direct microbiological evidence.
Frequently asked questions
The ELISA is a high-sensitivity screening test that detects total antibody reactivity to B. burgdorferi antigens. The Western Blot is the confirmatory tier-two assay that identifies reactivity to specific bacterial proteins by molecular weight, providing greater specificity. In the standard CDC two-tier algorithm, Western Blot is ordered only following a positive or equivocal ELISA — not as a standalone screening test.
How to access the Lyme Western Blot (IgG/IgM) test
The Lyme Western Blot (IgG/IgM) reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
Create Free AccountAbout this page
Published: May 22, 2026
Last reviewed: May 22, 2026
- Lantos PM, et al. Clinical Practice Guidelines by the Infectious Diseases Society of America, American Academy of Neurology, and American College of Rheumatology: 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease. Clin Infect Dis. (2021)
- Mead P, et al. Revised CDC Recommendation for Serologic Diagnosis of Lyme Disease. MMWR Morb Mortal Wkly Rep. (2019)
- Steere AC, et al. Lyme borreliosis. Nat Rev Dis Primers. (2016)
- Wormser GP, et al. The Clinical Assessment, Treatment, and Prevention of Lyme Disease, Human Granulocytic Anaplasmosis, and Babesiosis: Clinical Practice Guidelines by the Infectious Diseases Society of America. Clin Infect Dis. (2006)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.