What Is Lyme Disease?

Lyme disease is an illness caused by infection with a bacteria that is spread through the bite of certain kinds of ticks. Symptoms can affect the skin where the bite occurred or elsewhere on the skin and may progress to affect other parts of the body. A family of bacteria, known as Borrelia, causes Lyme disease.

The Role of Lyme Disease Tests

The purpose of the most common type of Lyme disease testing is to determine whether you have developed antibodies as a result of past exposure to the Borrelia bacteria that cause Lyme disease. Antibodies are proteins created by the immune system that target specific threats like bacteria and viruses.

Blood testing alone cannot determine whether you have Lyme disease. Instead, testing can provide helpful information that your doctor can consider along with other factors, such as any symptoms you’ve had and whether you’ve been exposed to ticks that can carry Borrelia, to determine if a diagnosis of Lyme disease is appropriate.

Beyond blood testing, it is possible to analyze fluid from the central nervous system for signs of the Borrelia bacteria.

Who should get testing?

Testing is usually indicated if a person has symptoms of Lyme disease and a known or possible exposure to ticks that can carry the Borrelia bacteria. However, because it takes time for antibodies to develop, the timing of testing is important to consider.

Lyme disease symptoms depend on the extent of the bacterial infection. Three phases are used to describe the infection:

  1. Early localized: In this initial phase, symptoms are normally found only near the tick bite. This early stage is called erythema migrans and involves a noticeable rash that typically develops within a few weeks after being bitten.
  2. Early disseminated: In this phase, the bacteria move through the blood to affect other parts of the body and can cause general symptoms like fever, headaches, and pain. In some cases, the bacteria can affect the heart or nervous system.
  3. Late disease: This phase occurs long after the initial tick bite and most often includes symptoms affecting the joints or nervous system.

It is important to understand these phases because testing is not equally valuable in each stage. With early localized disease and erythema migrans, blood testing is generally not helpful because antibodies have not had enough time to develop.

In people with symptoms of early disseminated or late disease, testing can help determine whether they have had a previous Borrelia infection. Blood testing alone, though, does not diagnose Lyme disease. It is one factor to be considered alongside symptoms and potential tick exposure.

Some symptoms of Lyme disease, like joint pain, can be caused by many other health conditions. For this reason, testing is not recommended if you only have these kinds of nonspecific symptoms and no other indications of Borrelia exposure. In these cases, a positive test can be misleading because antibodies could be the result of a past infection rather than an active condition causing your present symptoms.

Because of similar concerns about potential false positive results, random screening for Lyme disease in people without symptoms is not recommended even in areas that are known to have ticks that can carry the Borrelia bacteria.

Testing of the cerebrospinal fluid is most often indicated when a person has neurological symptoms consistent with Lyme disease and positive or inconclusive blood tests.

Getting test results

For a blood test or lumbar puncture, you will likely receive test results from your doctor. Your doctor may call you with results or schedule you for a follow-up office visit. Results may also be sent to you through an online health portal or in the mail.

For at-home blood tests that are sent to a lab, you usually get results a few business days after your sample is received. Results are often provided through a smartphone app or website.

Lyme disease tests are generally effective for determining whether someone has been exposed to Borrelia, but, like any medical test, they are not perfect. There are considerations that can affect the accuracy of tests and how they are interpreted.

  • Cross-reactivity: It is possible for antibodies to other bacteria to be detected by tests for antibodies to Borrelia. This is known as a false positive because the test shows Borrelia exposure when none actually occurred. A misleading positive result can also occur in patients who have previously had Lyme disease or who have received a vaccine for Lyme disease.
  • Standardization of interpretation: The CDC has issued guidelines for how to interpret antibody test results. Studies have found that laboratories that follow these guidelines produce more consistent and reliable analyses than laboratories that apply non-standard criteria.
  • Test timing: When the test is taken is important to consider because of the time it can take for different antibodies to develop and be detectable in the blood.

The laboratory and doctor can take these factors into account when interpreting your test results. Overall, testing is typically reliable in assessing bacteria exposure, but it is important to remember that this is distinct from a definitive diagnosis of Lyme disease.

Types of Lyme Disease Tests

Antibody titer tests for Lyme disease measure antibodies that are specific to the bacteria that can trigger the condition. Antibodies are part of the body’s immune response. Tests look for two types of antibodies, known as immunoglobulin M (IgM) and immunoglobulin G (IgG).

IgM antibodies usually peak within a few weeks after an infection with Borrelia bacteria and start to collapse 4-6 months after infection. IgG antibodies are slower to develop, beginning to show 4-6 weeks after exposure and may peak 4-6 months after exposure. While IgM tends to be associated with an active infection, both IgM and IgG can persist in the blood for many years.

The Centers for Disease Control and Prevention (CDC) recommends a two-stage or two-tiered test for these antibodies. If the initial blood test is positive for IgM or IgG antibodies associated with the Borrelia bacteria, a second test is done, often using different laboratory methods.

Testing for IgM and IgG can support the finding that you have been exposed to Borrelia, but this on its own does not prove whether or not you have Lyme disease.

Beyond blood testing, it is possible to analyze fluid from the central nervous system for signs of the Borrelia bacteria. This is also called cerebrospinal fluid (CSF) testing. CSF testing for Lyme disease is complex and cannot necessarily rule out a past or present Borrelia infection of the central nervous system. There are, however, many CSF findings which, combined with a patient’s history and physical exam, can be used by the physician to confirm the presence of a Lyme infection of the central nervous system. For the diagnosis of Lyme disease outside the central nervous system, blood testing is the preferred approach.

Follow-up testing may be necessary if testing is inconclusive. This could involve repeat blood tests or the use of different types of medical tests to rule out other health conditions. In people suspected of bacterial reinfection, imaging tests may be used to detect joint inflammation.

Getting Tested for Lyme Disease

Lyme disease testing is usually ordered by a doctor and is used when there are signs or symptoms consistent with Lyme disease.

A blood sample can be drawn in a doctor’s office or other medical setting. If a test of cerebrospinal fluid is needed, an outpatient procedure called a lumbar puncture can be done in a hospital. Samples are then analyzed in a credentialed laboratory.

At-home testing

Some options exist for at-home testing of antibodies related to Lyme disease. In general, these test kits require you to take a blood sample by pricking your fingertip. That blood sample is then sent to a laboratory where it is analyzed for IgM and IgG antibodies.

Comparing Tests

Blood samples analyzed with enzyme immunoassay, immunofluorescence assay, or the Western Blot method are the principal form of testing for Lyme disease. When appropriate, testing of cerebrospinal fluid may be beneficial.

The CDC has warned that some laboratories have offered unproven tests to detect Lyme disease. These tests have not been validated and have no demonstrated role in the diagnostic process. Examples of tests that may be faulty include:

  • PCR tests using blood or urine
  • Urine antigen tests
  • Lymphocyte transformation tests
  • Culture, immunofluorescence staining, or cell sorting of Borrelia bacteria
  • CD57 lymphocyte assays
  • IgG or IgM analysis other than with enzyme immunoassay, immunofluorescence assay, or the Western Blot method

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