Laboratory testing for Lyme disease: FAQs for general public
What is Lyme disease?
Lyme disease (Lyme borreliosis) is an infection caused by bacteria known as Borrelia (B. burgdorferi, B.garinii and B. afzelii). When this bacteria enters the body, the body’s defence system will attack and try to destroy it. The patient’s symptoms are the body’s attempts to get rid of the bacteria from the body.
What are the symptoms of Lyme disease?
Some people with Borrelia infection will have no symptoms. For those who have symptoms (Lyme disease) the illness is described as having three different stages.
1. Early localised disease:
In about three quarters of cases the patient develops a characteristic “bulls-eye” red rash (erythema migrans) spreading outwards from the site of a tick bite. The patient may also have vague 'flu-like' symptoms. The rash may be very faint and not easily noticed, especially if the bite was not in an obvious area. The rash and other symptoms can resolve even without antibiotics. However, treatment of Lyme disease with antibiotics at this stage is still advised to reduce the chance that the disease may progress.
2. Early disseminated disease:
During this stage the bacteria may spread around the body in the blood causing any of the following symptoms:
- severe flu-like illness
- multiple rashes like erythema migrans (usually smaller)
- facial nerve weakness, facial droop or other neurological problems in the head and neck
- meningitis (swelling of the layers around the brain)
- arthritis (swelling and pain in joints)
- heart problems
Treatment of Lyme disease with antibiotics at this stage is also advised.
3. Chronic disseminated disease:
Progress to this stage is uncommon but may occur in patients who did not receive enough treatment at an earlier stage. This stage most commonly involves joints, particularly the knee. A skin condition known as acrodermatitis chronica atrophicans (ACA) may occur at this stage. ACA is most evident on the hands and feet. It begins with bluish red discoloration of the skin and skin swelling. AC may last several months or years. As ACA progresses the skin may become thin, translucent and begins to wrinkle. Patients with chronic disseminated Lyme disease may not remember a tick bite as the bite may have occurred years previously at this late stage of infection.
How is Lyme disease spread?
The Borrelia bacteria are carried by infected ticks that feed on blood when they bite a person. The tick injects the bacteria into the person’s blood while feeding and this leads to infection.
How is Lyme disease treated?
Common antibiotics (such as doxycycline or amoxicillin) are effective at clearing the infection and early symptoms and in helping to prevent the development of complications. If untreated, the disease will progress to a longer-term form in about half of patients. Antibiotics are generally given for up to three weeks. If complications develop, intravenous antibiotics may need to be used to treat the infection. The bacteria can survive for long periods in the body even if no symptoms develop. If untreated, the bacteria can cause chronic irritation in in a number of the body’s organs. That is why early diagnosis and treatment with antibiotics is important.
How is Lyme disease diagnosed?
In general, if a patient attends their doctor with erythema migrans (Early Localised Disease) the doctor will be able to diagnose Lyme disease from this distinctive rash. Lyme blood tests are not necessary and at this stage of early infection tests may be negative. This is because blood tests for Lyme work by detecting antibodies to the Borrelia bacteria in the person’s bloodstream, and the body takes 2-4 weeks to produce these antibodies.
Antibodies are produced by the body's immune system when it detects harmful substances, such as bacteria. People have a wide variety of antibodies; each type of antibody is different and defends the body against a specific kind of infection. A person with Lyme disease will develop antibodies that recognise different parts of the Borrelia bacteria. However it can take about 2-4 weeks for this to happen. If a blood sample is taken at this early stage and is negative, then retesting in 2-4 weeks may be useful.
For Lyme disease at a later stage (Early Disseminated Disease/Chronic Disseminated Disease) the person’s immune system will have had time to develop antibodies which can be detected by laboratory tests. The current advice is that the diagnosis of Lyme disease should be made only after careful review of the patient's symptoms as well as the laboratory tests results and tick bite history. This is because many of the symptoms of these later stages of Lyme disease can be due to other illnesses or factors.
It is recommended to test for Lyme disease using two different types of blood tests, EIA (Enzyme immune assay) testing and Western Blot testing. The United States’ Centers for Disease Control and Prevention has an excellent explanation of the two-tier testing system.
1. Enzyme Immune Assay (EIA) testing:
This test detects antibodies to the different kinds of bacteria that are known to cause symptoms of Lyme disease. Different strains of Borrelia are found in the USA (B. burgdorferi senso stricto) and Europe (B. garinii, B. afzelii, B burgdorferi senso stricto) but the tests are designed to detect all of the Borrelia that cause symptoms.
The EIA is the first test performed as it is designed to be very “sensitive” (i.e. to correctly identify those people who have Lyme disease). If the EIA test is negative for Lyme disease, this can be relied upon to exclude Lyme disease in the patient, especially if the sample is taken when symptoms have been present for several weeks.
The disadvantage of the EIA is because it is very sensitive it can give “false positive” results. This means that the EIA test is reacting with something else present in the blood sample which is not related to Lyme disease. False positive EIA results can happen when there are infections with other bacteria or viruses, or in certain inflammatory /automimmune conditions. This is why a positive EIA test should be confirmed by a second test – the Western Blot.
In Ireland, 2.5% of over 4,800 people who were tested by the National Virus Reference Laboratory in a single year had a positive Lyme test result. In Europe, between 3- 5% of the general population show evidence of infection with Borrelia bacteria at some point in their lifetime while a study in Ireland previously found that the background rate of infection in the Irish population was 3.4%.
2. Western Blot:
If a patient’s EIA blood test results are positive (or questionable) for Lyme disease, the same blood sample is then tested using the Western Blot method. The Western Blot test is more specific to Lyme disease than the EIA test. The Western Blot confirms the presence of antibodies to a number of different parts (antigens) of the Borrelia bacteria. The presence of a variety of antibodies to different parts of the Borrelia bacteria confirm that the screening EIA result is a true positive. If a patient’s blood test results are negative by Western Blot, this can be relied upon to exclude Lyme disease in the patient. Other causes of the patient’s symptoms should be investigated.
Antibodies which develop following infection with Borrelia bacteria can remain detectable for life, even after the person has received treatment. Therefore, even a positive result confirmed by Western Blot showing that a person has been infected with Borrelia at some stage, may not be the reason for their symptoms at the time the test is performed. It is for this reason, that when blood tests are carried on a patient for Lyme disease, the symptoms and clinical features of the patient must always be considered by the physician.
How do patients test negative for Lyme disease in Ireland, but test positive for Lyme disease in another country?
Laboratories in Ireland generally follow the laboratory testing recommendations of the US Centres for Disease Control and Prevention (CDC), the Infectious Disease Society of America (IDSA), the European Federation of Neurological Societies (EFNS) and the British Infection Association (BIA).
The antibody tests used in Ireland are made by commercial companies and meet strict quality criteria. Irish laboratories have their own quality assurance methods to make sure the tests are working correctly as well as being accredited by the Irish National Accreditation Body (INAB) to perform the test correctly.
Testing which is performed abroad may be performed in laboratories which have not met National or International Accreditation (Quality Standards). In some cases they may use tests which are made in the laboratory rather than purchased from commercial companies. These tests may not have the same or consistent levels of quality as commercial tests which must meet specific European criteria called CE marking. These tests may be more likely to give a “false positive” result for those reasons.
Laboratories abroad may also interpret the results of tests using rules that are different than those used by laboratories in Ireland. These laboratories may diagnose Lyme disease on the basis of a single positive EIA test only without a second confirmatory test or on a pattern seen in the Western blot which does not meet the criteria for a positive test. Such diagnoses are not in agreement with international guidelines or the test’s manufacturer.
Some laboratories abroad do not use antibody tests like the EIA and western blot and instead will use other types of tests. For example, testing for levels of a specific white blood cell (CD-57) or lymphocyte transformation tests (tests to measure how specific cells in your immune system respond when exposed to B. burgdorferi antigens). These types of tests are not currently recommended by international groups such as the CDC, IDSA or BIA for a number of reasons:
- There is not enough scientific evidence that they are suitable tests to diagnose Lyme disease.
- There is no standard method to perform and interpret these kind of tests
- Positive results in these kinds of tests may be due to other underlying illnesses or conditions and not just Borrelia
Can I be assured that the type of Lyme disease testing carried out in Ireland is accurate?
Yes. Irish laboratories operate to a very high standard of quality. Laboratories in Ireland follow the testing guidelines of the US Centres for Disease Control and prevention (CDC), Infectious Disease Society of America (IDSA), European Federation of Neurological Societies (EFNS) and British Infection Association (BIA). These guidelines provide information on which of the currently available laboratory tests have enough evidence to accurately diagnose Lyme disease.
It is important that patients who are concerned about Lyme disease seek help and receive a firm diagnosis in Ireland to ensure continued medical care. It is important to ensure that your symptoms and lab results are considered together to make sure your diagnosis is as correct as possible.
If I am worried about Lyme disease who can I talk to?
Lyme disease is being increasingly recognised as causing illness and hardship, if the diagnosis is missed. Over the last number of years, there has been a marked increase in awareness of the condition among GPs and hospital doctors in Ireland. Each of the HSE’s Hospital Groups have a number of Infectious Disease Consultants who are expert in the diagnosis and management of Lyme disease. If you have been bitten by a tick or have other reasons to strongly suspect you may have Lyme disease, you should visit your GP for advice.
Last updated: 13 April 2017