Lyme Disease Diagnostic Blood Testing — What To Know
Lab Testing FAQs > All About Lyme Disease Testing
Lyme disease is the most common vector-borne disease (i.e. illness that is spread by mosquitoes, ticks, or fleas) in the United States. Each year, approximately 30,000 cases of Lyme disease are reported to the CDC, although experts estimate that the true number of cases diagnosed each year may be closer to 300,000.
Below, learn about Lyme disease transmission, symptoms, and testing options for patients.
What Is Lyme Disease?
Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted by infected Ixodes ticks, also known as deer ticks or black-legged ticks. These ticks can be as small as a poppy seed, making them very easy to miss after they have attached themselves to the body. Generally, ticks must be attached for at least 36 hours in order to transmit Lyme disease.
Early Lyme disease symptoms are flu-like in nature, and typically include fever, muscle aches, swollen lymph nodes, and fatigue. The characteristic bull’s-eye-shaped rash (known as erythema migrans) occurs in approximately 70 to 80 percent of infected persons, and begins at the site of the tick bite around 7 days after transmission.
As Lyme disease progresses, more severe symptoms may develop. These symptoms include facial palsy, arthritis with severe joint pain and swelling, nerve pain and numbness, inflammation of the brain and spinal cord, dizziness, and Lyme carditis (irregular heart beat).
Because of the nature of the symptoms associated with Lyme disease, patients are commonly misdiagnosed with fibromyalgia, rheumatoid arthritis, chronic fatigue syndrome, multiple sclerosis, depression, and various other conditions.
What Are the Most Common Lyme Disease Tests?
Lyme disease is notoriously difficult to diagnose. A combination of lab testing results, signs and symptoms, medical history, and risk of exposure to infected ticks should be considered when a patient is suspected of having Lyme disease.
The CDC recommends a two-step testing process for diagnosing Lyme disease, using blood tests that measure the patient’s antibody response. Both tests can usually be completed using the same blood sample:
- ELISA test: A screening test that detects antibodies to the bacterium Borrelia burgdorferi. This test may provide false-negatives (meaning the patient does in fact have Lyme disease, but received a negative test result), especially during the early stages of illness, when antibodies have not had time to develop.
- Western blot test: A secondary test that confirms the diagnosis of Lyme by detecting antibodies to several proteins of the bacterium Borrelia burgdorferi. Many experts consider this to be the most reliable Lyme disease test.
Keep in mind that these common Lyme diagnostic tests may yield both false-positives and false-negatives in certain instances. Antibodies can take several weeks to develop, so patients who are in fact infected with Lyme may receive a negative result if tested too early. Also, If patients are taking antibiotics at the time of the Lyme disease test, they may not produce enough antibodies to be detected by the test. It is estimated that 20-30% of Lyme-positive patients receive false-negative antibody tests.
On the other hand, various viral and autoimmune diseases may trigger a false-positive result for Lyme. This is why the two-step testing process is recommended, along with consideration of signs, symptoms, and exposure risk.
Are There Any Other Lyme Disease Tests?
There are three other tests that are sometimes used to diagnose Lyme disease, all of which are classified as “direct tests” because they detect the presence of the bacteria itself, rather than antibodies. These tests are:
- Polymerase chain reaction (PCR) test: Multiplies a key section of Lyme bacteria DNA so it can then be detected; however, many false negatives are reported.
- Antigen detection test: Detects a specific Lyme protein in body fluid (blood, urine, or joint fluid); can be useful for positively identifying patients who previously received a false negative.
- Culture testing: A sample of blood or other fluid is collected by the lab, who then attempts to grow Lyme spirochetes from the sample.
The above tests are less likely to be recommended by doctors than the ELISA test and the Western blot. If a patient suspects they may have Lyme disease but have received negative results on their antibody tests, it may be worthwhile to seek out a second opinion and acquire additional Lyme testing.
Who Should Get Tested for Lyme Disease?
If a patient believes they may have Lyme disease, it is important to receive a diagnosis and begin treatment quickly. Left untreated, Lyme disease may become chronic and could spread to other vital body systems. Any patient who has been bitten by a tick and is experiencing symptoms of Lyme disease should consult with their doctor as soon as possible.
Fortunately, most cases of Lyme disease can be treated successfully with a few weeks of antibiotics, and the majority of patients make a complete recovery. Lab testing is an important step in confirming or ruling out a Lyme disease diagnosis.
If a patient receives a negative initial test result but still suspects they may have Lyme, it is possible that they may have been tested too soon, before the antibodies had time to develop. In this case, the patient may consider retesting or pursuing other Lyme testing options.