Lyme disease is the most common tick-borne illness in the United States. It is a complex multisystem disease caused by infection with the spirochete Borrelia burgdorferi (Bb), transmitted by the bite of the deer tick (Ixodes scapularis). This infection elicits a series of predictable host immune responses which provide the basis for current serologic tests, the principle laboratory method for documenting Lyme infection.
The most commonly used tests are relatively insensitive in the very early stages of infection. The traditional western blot test improves the specificity during later stages of infection, but it too may lack both sensitivity and specificity in early infection.
The clinical value of these tests depends upon both inherent lab test performance characteristics, as well as, the pre-test likelihood of disease in the population being tested.(1) Screening asymptomatic or nonspecifically symptomatic individuals in whom the a priori probability of Lyme disease is low (such as patients with chronic fatigue, headaches, depression, arthralgias, or back pain) is not recommended. A positive test result in such patients, even in a highly endemic area, may not significantly increase the post-test probability that these patients have Lyme disease.(2)
To address the performance limitations of routine testing, a combination of both Antibody Capture EIA and Immunoblotting (WB) with interpretations is offered to provide more information to clinicians. IgM, IgG, and IgA antibody capture EIA results combined with immunoblotting (WB) detects a wider array of host immune responses to B. burgdorferi infection. Furthermore, the laboratory utilizes two different strains of B. burgdorferi for immunoblotting (WB). One is a wild strain isolated from a North American patient with Lyme disease, and one is a tick isolate mutant strain lacking the gene for the B. burgdorferi OspA protein. This is essential in evaluating patients suspected of having Lyme disease who may have received past Lyme vaccine (which consisted of recombinant single protein OspA).
Clinicians are frequently confronted with patients presenting with unexplained febrile illnesses, rashes, swollen joints, or neurologic symptoms (such as cranial nerve palsies or suspected meningitis). There are also challenging patients with persistent nonspecific symptoms after being treated for well-documented Lyme disease, and patients who develop new symptoms raising the suspicion for re-infection. The combination of antibody capture EIA and immunoblotting (WB) in most cases can assist the clinician in assessing these situations and lead to the correct diagnosis.
Early Lyme disease, if presenting with classic features (EM rash) in an endemic area, is diagnosed straightforwardly. Diagnosis is more challenging however if symptoms are not typical, and laboratory testing is indicated. Most patients (~90%) symptomatic with B. burgdorferi infection are seropositive, demonstrating an initial IgM response best shown by antibody capture EIA. If a patient is suspected of having early Lyme disease is initially seronegative, repeat follow-up testing is very useful. The evolution of the host immune response to B. burgdorferi infection is typically very quick. In as short a time as a week or two, an initially seronegative patient can develop robust seropositivity. The IgA response on antibody capture EIA is noted in early infection as well. Unlike the IgM and IgG response (which may persist), IgA levels usually fall rapidly with effective treatment and infection resolution, often becoming undetectable within the first few months. In that early “window” of an infection, when a patient is sometimes acutely symptomatic but prior to developing a detectable serologic response, it is possible with PCR technology to detect the DNA of B. burgdorferi in a whole blood specimen. It has been our observation that this window of B. burgdorferi bacteremia is brief, and by the time the patient has developed the characteristic serologic response, whole blood PCR testing for Lyme will have become negative.
Late Lyme disease may present with various neurological or musculoskeletal symptoms, and lacks truly pathognomonic features. In these situations, laboratory confirmation of infection provides the clinician with invaluable assistance. By late in the infection, isotype switching has occurred and significant levels of IgG specific antibodies are easily detectable by both antibody capture EIA and immunoblotting (WB). IgM and IgA are variably present in late untreated patients. The serologic characteristics are usually unambiguous for most patients with late stage infection. In addition to serologic testing, B. burgdorferi DNA may be directly detected, especially in the synovial fluid (SF) of patients with Lyme arthritis, occasionally in the CSF in cases of neuroborreliosis, and rarely if ever in whole blood late in the infection.
No evidence of Lyme disease, a “negative” test, is manifest by the absence of significant laboratory findings by antibody capture EIA and by IgG immunoblotting (WB). It is not uncommon to observe reactivity to a few antigens (bands) by immunoblots, reflecting past exposure to other microbial infections. This faint cross-reactivity does not constitute serologic evidence of Lyme disease. Similarly, a borderline or low level of IgM response, as the sole laboratory finding, in patients with chronic symptoms (4-6 weeks or longer) does not constitute evidence of recent or active Lyme infection as an explanation of a patient’s symptoms. This finding is often due to cross-reactive antibodies induced by another infection or condition (e.g. EBV, VZV, syphilis, dermatomyositis).
In summary, in early Lyme infection, within a few weeks, an IgM antibody response is detected by antibody capture EIA. This is followed by isotype switching and the evolution of an IgA and IgG response.(3) The IgA levels decrease first with resolution, and depending on when treatment is instituted and other factors, the IgM and IgG response may persist for variable periods of time, up to decades. Recognition of these principles and patterns of antibody response and serologic findings can help clinicians avoid the problems and adverse consequences of misdiagnosis and overdiagnosis (and overtreatment) of Lyme disease.(4)
The Imugen laboratory offers a comprehensive Lyme Antibody Analysis which includes IgM, IgG, and IgA antibody capture EIA, IgG immunoblotting (WB) on 2 strains of B. burgdorferi, and PCR testing on SF, CSF, and whole blood.
The staff at the laboratory is highly trained in performing and interpreting these assays, has decades of experience in analyzing these test results in the context of various clinical situations, and is available to assist healthcare providers in interpreting tests and answering questions about the detection of tick-borne infections.
1. Nichol G, Dennis DT, Steere AC, Lightfoot R, Wells G, Shea B, Tugwell P. Test Treatment Strategies for Patients Suspected of Having Lyme Disease: A Cost Effectiveness Analysis. Ann Intern Med 1998;128:37-48
2. American College of Physicians Position Paper. Clinical Guideline, Part 1: Guidelines for the Laboratory Evaluation in the Diagnosis of Lyme Disease. Ann Intern Med 1997;127:1106-1108
3. Berardi VP, Weeks K, Steere AC. Serodiagnosis of Early Lyme Disease: Analysis of IgM and IgG Antibody Responses by an Antibody Capture Enzyme Immunoassay. J Infect Dis 1988;158:754-760
4. Reid MC, Schoen RT, Evans J, Rosenberg JC, Horwitz RI. The Consequences of Overdiagnosis and Overtreatment of Lyme Disease; An Observational Study. Ann Intern Med 1998;128:354-362