Is there a blood test for lyme disease in humans? How accurate is blood test for lyme disease? how long does a blood test for lyme disease take? Is a new blood test for lyme disease? and many question that we want to know.
Before we talk about that, you should know that Lyme Disease is a clinical diagnosis. It is diagnosed based on your symptoms, medical history, and exposure to ticks. (Read more: lyme disease definition). If you undergo a test, a negative test result does not mean you do not have Lyme disease. Why? It is because the typical diagnostic tests for Lyme disease are so insensitive. There are many causes why someone who actually has Lyme disease in his body may have a negative test result. It may not have been time for antibodies to evolve, suppressed the immune system, or the person may be contaminated with a strain that the exam can not be measured. Lyme disease is known to inhibit the immune system, and 20-30% of patients have falsely negative antibody tests.
The tests can not only contribute on diagnosing a disease, but also to manage the illness. A good test can help a doctor evaluate the severity of sickness, estimate the prognosis of the patients, observe the progression of the disease, stability or resolution, detect relapse, and choose drugs or adjustment therapy. Unfortunately, a test like this capability does not exist for Lyme disease.
Lyme disease tests are used to assess if a person who experience specific symptoms and signs has been contaminated by the bacteria Borrelia mayonii or Borrelia burgdorferi. The tests can detect antibodies that are produced by the immune system in response to the infection.
Lab tests can find two different classes of antibody, IgM (immunoglobulin M) and IgG (immunoglobulin G).
- Borrelia IgM antibodies are usually detectable in the blood about two to three weeks after the infection. The levels of IgM gain to maximum concentrations at about six weeks and then it begins to decline.
- IgG antibodies are not detectable until several weeks after its exposure. It will increase to maximum levels at about four to six months, and may remain at high levels for several years.
Two Tier Blood Test for Lyme Disease in Humans
Today, the CDC suggests a two-step process when testing blood for the clue of antibodies against the bacteria of Lyme disease. Both steps can be performed using the same blood sample.
The first phase process uses a testing procedure called Enzyme Immunoassay (EIA) or rarely, an immunofluorescence assay (IFA). If the result of the first phase is negative, no further examination of the specimen is recommended. If the outcome is positive or indeterminate (sometimes called "equivocal"), the second move should be done. The second move uses an examination called an immunoblot test, commonly, a “Western blot” test. Results are counted positive only if the EIA or IFA test and the immunoblot test are both positive.
It is important to know that the two tier steps of Lyme disease examination are designed to be performed together. The CDC does not encourage skipping the first test and just doing the Western blot test. If the first test is not done, It will increase the frequency of false positive outcomes and may lead to misdiagnosis and inadequate treatment.
It is said that new tests may be developed as an alternative to one or both steps process. Before CDC will suggest new tests, its performance must be showed to be equal to or better than the results of the existing test. It also must be FDA approved.
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| two-tiered blood test for Lyme disease image source: cdc.gov |
The image above shows the steps required properly test for Lyme disease. The first required test is the EIA or IFA. If this trial gives negative outcomes, the physician should reconsider an alternative diagnosis. The physician may treat the patient and follow up with a convalescent serum in cases where the patient has had symptoms and signs for less than or equal to 30 days.
There are two options are available if the first test generates positive or equivocal outcomes. They are:
- IgM Western Blot can be performed if the patient has had symptoms for less than or equal to 30 days.
- IgG Western Blot may be done if the patient has had symptoms for more than 30 days. The IgM Western Blot should not be performed if the patient has been ill for more than 30 days.
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