Diagnostic Tests for Lyme disease

Diagnostic Test list for Lyme disease: The list of diagnostic tests mentioned in various sources as used in the diagnosis of Lyme disease includes:

Tests and diagnosis discussion for Lyme disease: Lyme disease may be difficult to diagnose because many of its symptoms mimic those of other disorders. In addition, the only distinctive hallmark unique to Lyme disease-the erythema migrans rash-is absent in at least one-fourth of the people who become infected. The results of recent studies indicate that an infected tick must be attached to a person's skin for at least 2 days to transmit the Lyme bacteria. Although a tick bite is an important clue for diagnosis, many patients cannot recall having been bitten recently by a tick. This is not surprising because the tick is tiny, and a tick bite is usually painless.

When a patient with possible Lyme disease symptoms does not develop the distinctive rash, a physician will rely on a detailed medical history and a careful physical examination for essential clues to diagnosis, with laboratory tests playing a supportive role.¹

Blood Tests. Unfortunately, the Lyme disease microbe itself is difficult to isolate or culture from body tissues or fluids. Most physicians look for evidence of antibodies against B. burgdorferi in the blood to confirm the bacterium's role as the cause of a patient's symptoms. Antibodies are molecules or small substances tailor-made by the immune system to lock onto and destroy specific microbial invaders.

Some patients experiencing nervous system symptoms may also undergo a spinal tap. Using this procedure, doctors can detect brain and spinal cord inflammation and can look for antibodies or genetic material of B. burgdorferi in the spinal fluid.

The inadequacies of the currently available diagnostic tests may prevent physicians from firmly establishing whether the Lyme disease bacterium is causing a patient's symptoms. In the first few weeks following infection, antibody tests are not reliable because a patient's immune system has not produced enough antibodies to be detected. Antibiotics given to a patient early during infection may also prevent antibodies from reaching detectable levels, even though the Lyme disease bacterium is the cause of the patient's symptoms.

The antibody test used most often is called an ELISA test. When an ELISA is positive, it should be confirmed with a second, more specific test, called a Western blot.

Physicians must rely on their clinical judgment in diagnosing someone with Lyme disease even though the patient does not have the distinctive erythema migrans rash. Such a diagnosis would be based on the time of year, history of a tick bite, the patient's symptoms, and a thorough ruling out of other diseases that might cause those symptoms. Doctors may consider such factors as an initial appearance of symptoms during the summer months when tick bites are most likely to occur, and outdoor exposure in an area where Lyme disease is common.

New Tests Under Development. To improve the accuracy of Lyme disease diagnosis, NIH-supported researchers are developing a number of new tests that promise to be more reliable than currently available procedures.

NIH scientists are developing tests that use the highly sensitive genetic engineering technique, known as polymerase chain reaction (PCR), to detect extremely small quantities of the genetic material of the Lyme disease bacterium in body tissues and fluids.

A bacterial protein, outer surface protein (Osp) C, is proving useful for the early detection of specific antibodies in people with Lyme disease. ¹

The diagnosis of Lyme disease is based primarily on clinical findings, and it is often appropriate to treat patients with early disease solely on the basis of objective signs and a known exposure. Serologic testing may, however, provide valuable supportive diagnostic information in patients with endemic exposure and objective clinical findings that suggest later stage disseminated Lyme disease. When serologic testing is indicated, CDC recommends testing initially with a sensitive first test, either an enzyme-linked immunosorbent assay (ELISA) or an indirect fluorescent antibody (IFA) test, followed by testing with the more specific Western immunoblot (WB) test to corroborate equivocal or positive results obtained with the first test. Although antibiotic treatment in early localized disease may blunt or abrogate the antibody response, patients with early disseminated or late-stage disease usually have strong serological reactivity and demonstrate expanded WB immunoglobulin G (IgG) banding patterns to diagnostic B. burgdorferi antigens. Antibodies often persist for months or years following successfully treated or untreated infection. Thus, seroreactivity alone cannot be used as a marker of active disease. Neither positive serologic test results nor a history of previous Lyme disease assures that an individual has protective immunity. Repeated infection with B. burgdorferi has been documented. B. burgdorferi can be cultured from 80% or more of biopsy specimens taken from early erythema migrans lesions. However, the diagnostic usefulness of this procedure is limited because of the need for a special bacteriologic medium (modified Barbour-Stoenner-Kelly medium) and protracted observation of cultures. Polymerase chain reaction (PCR) has been used to amplify genomic DNA of B. burgdorferi in skin, blood, cerobro-spinal fluid, and synovial fluid, but PCR has not been standardized for routine diagnosis of Lyme disease. ²

Footnotes:
1. excerpt from Lyme Disease - The Facts, The Challenge: NIAID
2. excerpt from Lyme Diagnosis: DVBID

Last revision: June 2, 2003

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