Description

The Diagnostic Automation, Inc Borrelia burgdorferi IgM ELISA kit is an enzyme-linked immunosorbent assay (ELISA) for the qualitative presumptive detection of IgM antibodies to Borrelia burgdorferi in human serum. This ELISA test should only be used for patients with signs and symptoms that are consistent with Lyme disease. Equivocal or positive results must be supplemented by testing with a standardized Western Blot procedure. Positive supplemental results are supportive evidence of exposure to B. burgdorferi and can be used to support a clinical diagnosis of Lyme disease.

Borrelia burgdorferi is a spirochete that causes Lyme disease. The organism is transmitted by ticks of the genus Ixodes. In endemic areas, these ticks are commonly found on vegetation and animals such as deer, mice, dogs, horses, and birds. B. burgdorferi infection shares features with other spirochetal infections (diseases caused by three genera in humans: Treponema, Borrelia, and Leptospira). Skin is the portal of entry for B. burgdorferi and the tick bite often causes a characteristic rash called erythema migrans (EM). EM develops around the tick bite in 60% to 80% of patients. Spirochetemia occurs early with wide spread dissemination through tissue and body fluids. Lyme disease occurs in stages, often with intervening latent periods and with different clinical manifestations.

In Lyme disease there are generally three stages of disease often with overlapping symptoms. Symptoms vary according to the sites affected by the infection such as joints, skin, central nervous system, heart, eye, bone, spleen, and kidney. Late disease is most often associated with arthritis or CNS syndromes. Asymptomatic subclinical infection is possible and infection may not become clinically evident until the later stages.

Patients with early infection produce IgM antibodies during the first few weeks after onset of EM and produce IgG antibodies more slowly. Although IgM only may be detected during the first month after onset of illness, the majority of patients develop IgG antibodies within one month. Both IgG and IgM antibodies can remain detectable for years.

Isolation of B. burgdorferi from skin biopsy, blood, and spinal fluid has been reported.
However, these direct culture detection methods may not be practical in the large scale diagnosis of Lyme borreliosis. Serological testing methods for antibodies to B. burgdorferi include indirect fluorescent antibody (IFA) staining, immunoblotting, and enzyme immunoassay (EIA). B. burgdorferi is antigenically complex with strains that vary considerably. Early antibody responses often are to flagellum which has cross reactive components. Patients in early stages of infection may not produce detectable levels of antibody. Also, early antibiotic therapy after
EM may diminish or abrogate good antibody response. Some patients may never generate detectable antibody levels. Thus, serological tests for antibodies to B. burgdorferi are known to have low sensitivity and specificity and because of such inaccuracy, these tests cannot be relied upon for establishing a diagnosis of Lyme disease.

The Diagnostic Automation, Inc. Borrelia burgdorferi ELISA Kit is designed to detect IgM class antibodies to B. burgdorferi in human sera. Wells of plastic microwell strips are sensitized by passive absorption with B. burgdorferi antigen. The test procedure involves three incubation steps:
1.Test sera are diluted with the Sample Diluent provided. The Sample Diluent contains
antihumanIgG which precipitates and removes IgG and rheumatoid factor from the sample leaving IgM free to react with the immobilized antigen. During sample incubation, any antigen specific IgM antibody in the sample will bind to the immobilized antigen. The plate is washed to remove unbound antibody and other serum components.
2. Peroxidase Conjugated goat anti-human IgM (μ chain specific) is added to the wells and the plate is incubated. The Conjugate will react with IgM antibody immobilized on the solid phase in step 1. The wells are washed to remove unbound Conjugate.
3. The microwells containing immobilized peroxidase Conjugate are incubated with peroxidase Substrate Solution. Hydrolysis of the Substrate by peroxidase produces a color change. After a period of time the reaction is stopped and the color intensity of the solution is measured photometrically. The color intensity of the solution depends upon the antibody concentration in the original test sample.

In 1994, the Second National Conference on Serological diagnosis of Lyme disease recommended a two-step testing system toward standardizing laboratory serologic testing for B. burgdorferi. Because EIA and IFA methods were not sufficiently specific to support clinical diagnosis, it was recommended that positive or equivocal results from a sensitive EIA or IFA (first step) should be further tested, or supplemented, by using a standardized Western Blot method (second step) for detecting antibodies to B. burgdorferi (Western Blot assays for antibodies to B. burgdorferi are supplemental rather than confirmatory because their specificity is less than optimal, particularly for detecting IgM). Two-step positive results provide supportive evidence of exposure to B. burgdorferi, which could support a clinical diagnosis of Lyme disease but should not be used as a sole criterion for diagnosis.