Utilizing the Laboratory for Diagnosis


 Vector-borne Disease Series
1998 Number I

Utilizing the Laboratory for the Diagnosis of Lyme Disease

Philip J. Molloy, MD, FACP
Medical Director

Lyme disease is the most common tick-borne disease in the United States. It is a complex multi-system disease which results in predictable host immune responses. These responses are the basis for all current valid serologic tests.

Due to both the disease's complexity and the performance characteristics of the tests most commonly used, sound principles of test ordering are essential. The most simple and available test, the ELISA, is both insensitive in the early stages of infection and lacks the required specificity to be used as a reliable diagnostic test. Immunoblotting, while improving the specificity for the diagnosis during the later stages of infection, also lacks both specificity and sensitivity in cases of early infection. In order to address these limitations, a combination of both antibody capture enzyme immunoassay (EIA) and immunoblotting, with proper interpretations, can provide highly useful information to the clinician. (Capture EIA testing evaluates IgM, IgG and IgA).

Is my patient's rash, febrile illness, swollen knee, Bell's palsy, or other neurologic complaint, a symptom of Lyme disease? What about my patient's joint pain or synovitis? Is it, too, a symptom of Lyme disease? Does my patient remain infected although he was diagnosed and treated a year ago? The combination of antibody capture and western blotting can, in most cases, help answer these common diagnostic questions.

The clinical usefulness of a test is determined not only by the test performance characteristics, but also by the pre-test likelihood of Lyme disease in the population being tested.(2) Neither screening asymptomatic subjects nor testing subjects in whom the prior probability of disease is exceedingly low (such as patients with chronic nonspecific fatigue, headache, depression, and back pain) is indicated. In such patients, the pre-test probability of Lyme disease is so low that a positive test result does not significantly increase the likelihood that these patients have Lyme disease.(3) This is true even in a highly endemic area.

Early Lyme Disease which presents with classical clinical features makes the diagnosis, especially in highly endemic areas, relatively straightforward. However, in many cases the classic clinical features are absent, making diagnosis more challenging. The typical serologic profile of a patient with early infection, is an elevated IgM capture Enzyme Immunoassay (EIA) response, seen in 91% of subjects with culture positive erythema migrans (EM).(1)

Late Lyme Disease lacks truly pathognomonic features, has varied manifestations, and may be confused with many other diseases. Because of this, laboratory confirmation oftentimes provides the clinician with invaluable assistance.

No Evidence of Lyme Disease

The typical serologic profile of a patient with no immune response to B. Burgdorferi (Bb) is the absence of significant Lyme specific antibodies of all three isotypes by antibody capture EIA. It is not uncommon to see weak immunoblot reactivity to a few antigens (i.e. "bands"), reflecting past exposure to other microbial antigens. These few weak bands do not constitute serologic evidence of Lyme infection. An isolated low IgM response in the capture assay, in patients with chronic non-specific symptoms, might reflect residual Bb antibody from a remote treated infection, or it may be reflective of cross reactivity with other infectious agents (e.g. EBV, VZV). When such an IgM response is due to a genuine early Lyme infection, the IgM level will quickly rise, typically followed by an "isotype switch" with the evolution of specific IgA and IgG responses. When an initial low IgM level is present and is due to cross-reactivity, it will remain low and there will be no evolution of additional Lyme specific antibodies.

Recognition of these principles and pattern of antibody responses can help the physician avoid the problems and adverse consequences of overdiagnosis (and overtreatment) of Lyme disease.(4)

The following is a classic example of a patient, diagnosed in February 1998, with late disseminated Lyme disease. He was referrred by his primary care physician to a specialist with acute synovitis (swollen knee). When appropriate laboratory tests were used, there was no reason for confusion regarding the diagnosis of late stage lyme disease. The typical serologic profile reveals a high IgG antibody response, variable capture responses by IgM and IgA, and an intense, expanded immunoblot response, as shown in the example below. A negative or equivocal serologic profile would virtually eliminate Lyme disease as the cause of this patient's swollen joint.
Antigen Antibody
Isotype		 Results
Serum #
98XXXX
Collection Date:
4/09/98
B. burgdorferi
G39/40
IgM <1
IgG <1
IgA <1
Normal Range: <1

Comments: No IgM, IgG, or IgA antibosy to B. burgdorferi detected by capture EIA. The IgG immunoblot finding are not significant.

Interpretation: These results fail to provide serologic evidence of infection with B. burgdorferi.

Immunoblot (IgG)
B. burgforferi
G39/40

Figure 2: Results of antibody capture EIA and western blot on a serum from a patient with chronic non-specific complaints. Immunoblot results reveal reactivity to a few borrelia proteins, a finding in itself, not consistent with B. burgdorferi infection.
Antigen Antibody
Isotype		 Results
Serum #
98XXXX
Collection Date:
2/23/98
B. burgdorferi G39/40
IgM 3.3
IgG 41.7
IgA 2.1

Immunoblot (IgG)
B. burgdorferi 39/40
Normal Range: <1

Comments: Significant levels of IgM, IgG, and IgA antibody to B. burgdorferi detected by capture EIA with significant IgG immunoblot findings.

Interpretation: These results are diagnostic of an active or recently active late stage infection with B. burgdorferi.
Figure 1: Results of capture EIA and western blot on a serum from a patient with active Lyme synovitis. Immunoblot results are molecular weights in kDa of borrelia proteins with which patient antibody is reactive.

REFERENCES:

1. Berardi VP, Weeks KE, Steere AC. "Serodiagnosis of Early Lyme Disease: Analysis of IgM and IgG Antibody Responses by an Antibody Capture Enzyme Immunoassay." J Infect Dis 1988;158:754-60

2. Nichol G, Dennis DT, Steere AC, Lightfoot R, Wells G, Shea B, Tugwell P. "Test Treatment Strategies for Patients Suspected of Havin Lyme Disease: A Cost Effectiveness Analysis." Ann Intern Med 1998;128:37-48

3. 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

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

In contrast, the results below do not suggest exposure to B. burgdorferi. This patient presented with chronic osteoarthritis and fatigue, but lacked specific Lyme symptoms. Healthy, asymptomatic controls from non-endemic regions exhibit similar test results. The appearance of a few "bands", without additional indicators, does not suggest infection with B. burgdorferi.


Questions related to the laboratory diagnosis of tick-borne diseases may be directed to the professional staff at IMUGEN.


 


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