Lyme diagnosis and testing can be very confusing. This confusion has contributed to false positive diagnoses and unnecessary treatment.
As in other infections like HIV, testing for Lyme disease involves looking for antibodies produced by the body’s immune system in response to infection. This is called serologic testing because the antibodies are found in blood serum.
Testing positive for antibodies is called seropositive and testing negative for antibodies is called seronegative.
Lyme disease testing: Useful when performed appropriately
One known problem is that we can produce antibodies for years or decades after a Lyme infection has been eradicated. Therefore, a seropositive test on its own is not necessarily indicative of active infection.
In addition, it can take a few weeks for detectable antibodies to build up in the body. Pseudoscience advocates frequently mislead about Lyme antibody testing by failing to differentiate testing performance in early infection from testing performance in late infection.
Below is a CDC-produced illustrative example of antibody production in Lyme disease, which triggers a positive test once a detection threshold is reached.
Two types of antibodies are shown: IgG and IgM. Typically, a detectable IgM antibody response is produced first, followed by a detectable IgG response.
Some guidelines from CDC:
- Patients who have had Lyme disease for longer than 4-6 weeks, especially those with later stages of illness involving the brain or the joints, will almost always test positive.
- A patient who has been ill for months or years and has a negative test almost certainly does not have Lyme disease as the cause of their symptoms.
- Serologic testing is generally not useful or recommended for patients with single EM rashes. For this manifestation, a clinical diagnosis (alone) is recommended.
Since IgG antibodies are detectable after 4-6 weeks of infection, experts echoed CDC in concluding:
Immunoglobulin G (IgG) seronegativity in an untreated patient with months to years of symptoms essentially rules out the diagnosis of Lyme disease, barring laboratory error or a rare humoral immunodeficiency state.
Beware IgM false positives
IgM Lyme testing is notorious for producing false positive results, which is why it is only used in very limited circumstances, i.e. during the first 30 days of illness before detectable IgG antibodies would be produced in the event of a Lyme infection.
The CDC diagnosis and testing page states:
Positive IgM results should be disregarded if the patient has been ill for more than 30 days.
The CDC Lyme FAQ addresses how to interpret long-lasting symptoms where an IgG test was negative but the IgM test was positive:
If you have been infected for longer than 4 to 6 weeks and the IgG Western Blot is still negative, it is highly likely that the IgM result is incorrect (e.g., a false positive). This does not mean that you are not ill, but it does suggest that the cause of illness is something other than the Lyme disease bacterium.
Experts agree around the world
A strong scientific consensus is evident about Lyme disease diagnosis and testing.
A 2018 French review of 16 Lyme diagnostic guidelines from 7 countries “revealed a global consensus regarding diagnosis at each stage of the infection.” The only outlier was the pseudoscience group German Borreliosis Society (Deutsche Borreliose-Gesellschaft, DBG), a German counterpart to the pseudoscience group ILADS.
Independent studies show testing accuracy in late stage
A 2016 systematic review  that included 8 studies of CDC-recommended two tier test performance in “Late Lyme” showed Lyme antibody testing to be 99.4% sensitive and 99.3% specific** in North America.
In other words, out of 100 people with Late Lyme disease, 99-100 of them will test positive. Out of 100 people who may believe they have Late Lyme disease but do not, 99-100 of them will test negative.
Misinformation can convince patients to ignore or misinterpret negative tests to justify a false “Chronic Lyme” diagnosis.
Avoid unnecessary and unscientific testing
Don’t test for Lyme disease as a cause of musculoskeletal symptoms without an exposure history and appropriate exam findings. 
As discussed in the CDC video below, determining the pretest probability of Lyme disease is very important:
Experts also warn against unvalidated testing [5, 9]. Quackwatch  and Science-Based Medicine  both provide accessible explanations about the differences between validated and unvalidated tests.
How Lyme antibody testing works
Antibody testing for Lyme disease requires two different tests to establish a positive result. If either the first tier test or the second tier test is negative, the test result is negative overall.
But in the event of a negative result, Dr. Adriana Marques of the NIH states:
For patients with signs or symptoms consistent with Lyme disease for less than or equal to 30 days, the provider may treat the patient and follow up with testing of convalescent-phase serum.
The first tier of the “two-tiered testing” system is an Enzyme Immunoassay (EIA aka ELISA).
The second tier of the well-established Standard Two-Tiered Testing (STTT) involves IgM and IgG Western Blot tests, which can be complicated to understand. The Western Blot is also called an immunoblot or a line blot.
New tests FDA-cleared and CDC-recommended!
In 2019, CDC added a second test system to its recommended tests, the Modified Two-Tiered Test (MTTT). In the MTTT, the second tier is a different ELISA that is FDA-cleared specifically for the MTTT.
By using the MTTT, testing is simpler, costs may be reduced, and Lyme disease is more likely to be detected in the first weeks of infection.
A drawback of the MTTT is that potentially useful information is no longer determined about which types of antibodies are being produced by the body.
See also: Lyme testing algorithm flow charts by Dr. Adriana Marques
More about Western Blot testing in North America
The IgG Western Blot test is designed to detect antibodies specific to Borrelia burgdorferi, the bacteria that cause Lyme disease. For Lyme disease in North America, a positive IgG Western Blot test requires at least 5 of 10 measured “bands” to be positive (or reactive).
The scored IgG bands are 18 kDa, 24 kDa (OspC)†, 28 kDa, 30 kDa, 39 kDa (BmpA), 41 kDa flagellin (Fla), 45 kDa, 58 kDa (not GroEL), 66 kDa, and 93 kDa.
The Lyme IgM Western Blot test measures 3 different types of antibodies. The North American IgM Western Blot is considered positive only if 2 of 3 IgM bands are positive (or reactive).
The scored IgM bands are 24 kDa (OspC)†, 39 kDa (BmpA), and 41 kDa (Fla).
As discussed above, the IgM Western Blot should only be used in the first 30 days of illness.
† According to CDC, “Depending upon the assay, OspC could be indicated by a band of 21, 22, 23, 24 or 25 kDA.”
Important: Don’t misinterpret a negative test as positive
Many people without Lyme disease will test positive for some bands. Therefore, CDC cautions:
It is not correct to interpret a test result that has only some bands that are positive as being “mildly” or “somewhat” positive for Lyme disease.
For example, in one study, 43% of healthy people and 75% of syphilis patients tested positive for IgG band 41. In a study of US veterans in New York, 76% of those without Lyme disease tested positive for IgG band 41. In a 1996 study, in healthy people, 55% and 21% tested positive for IgG band 41 and IgM band 41, respectively.
Even without a Borrelia burgdorferi infection, many of us produce antibodies that will react on a Lyme test. Notably, harmless bacteria found naturally in our mouths can cause us to test positive for band 41.
Both tiers are important
A positive Lyme antibody test requires both tiers to be positive, as many without Lyme infections can test positive on single tests. For example, one study found up to 40% of patients with Lupus and other rheumatic diseases test positive on the first tier ELISA test. The second tier test is necessary to stop a false positive diagnosis.
The American Society for Microbiology recommends against ordering the Western blot without a positive ELISA screening:
The Lyme immunoblot test is designed only as a confirmatory test, so it is important not to test screen-negative samples.
LymeScience recommends against:
- Tests from any of the following labs: IgeneX, DNA Connexions, Galaxy Diagnostics, Medical Diagnostic Laboratories (MDL), Milford Molecular Diagnostics Laboratory, Advanced Lab, Fry Laboratories, Ceres Nanosciences (Nanotrap), Global Lyme Diagnostics, Pharmasan Labs (iSpot Lyme), Coppe Laboratories (myLymeTest), ArminLabs, BCA-Lab (also known as InfectoLab), Australian Biologics, Melisa Labs, Moleculera Labs (Cunningham Panel), R.E.D. Labs, Immunosciences Lab, Aperiomics, Te?ted Oy (Tezted Limited, TICKPLEX), Lyme Diagnostics Ltd. (DualDur cell technology), ProGene (DX Genie), Ionica Sciences (IonLyme), T Lab Inc., Veramarx, Vibrant America/Vibrant Wellness, Research Genetic Cancer Centre (RGCC)/Biocentaur (PaLDiSPOT, PrimeSpot), Nordic Laboratories
- Any lab on Quackwatch’s list of “Laboratories Doing Nonstandard Laboratory Tests“
- CD57 testing
- Diagnosis with microscopy, e.g. Live Blood Cell Analysis.
- Diagnosis based on magical beliefs, for example applied kinesiology a.k.a Autonomic Response Testing (ART)
- Urine tests
- Electrodermal testing
- Lymphocyte Transformation Test (LTT)
- ELISpot and interferon gamma tests
- MELISA testing
- Phelix Phage tests
- Failing to follow testing strategies recommended by CDC or local infectious diseases organizations
- Failing to perform and acknowledge both tests of the established two-tiered test
- Using testing that is not cleared or approved by the FDA
- Clinical diagnosis without a science-based rationale
- Diagnosis via a questionnaire of non-specific symptoms
- Diagnosis from an unscientific practitioner, including those who market themselves using the following terminology: Lyme literate (especially those affiliated with ILADS), integrative, functional, alternative, complementary, Traditional Chinese Medicine, holistic, natural, Biological, Ayurvedic, chiropractic, naprapathic, homeopathic, and naturopathic
- Diagnosis from a psychic, energy healer, shaman, or practitioner of muscle testing (aka ART-Autonomic Response Testing or applied kinesiology)
- Direct-to-consumer testing that hasn’t been ordered by a medical provider
- Relying on Clinical Laboratory Improvement Amendments (CLIA) certification as an indication that a test result is legitimate (see CDC discussion)
- Any testing not recommended by CDC
Scenarios for which Lyme disease serologic testing is NOT recommended include:
- Presence of erythema migrans in high incidence areas.
- Absence of likely Ixodes tick exposure (CDC: Regions Where Ticks Live)
- Lack of travel to, or residence in a Lyme disease endemic area (CDC: Lyme Disease Maps).
- Following completion of one or more antibiotic course(s) for Lyme disease:
- Testing should not be used to monitor response to therapy or determine ‘cure.’
- Due to pressure from patient or patient representatives in the absence of clinical criteria supporting risk for Lyme disease infection.
Experts from the American College of Rheumatology, American Academy of Neurology, and Infectious Diseases Society of America also recommend against† routine Lyme testing for people with various non-Lyme conditions such as:
- Asymptomatic person following a tick bite
- Amyotrophic lateral sclerosis
- Relapsing-remitting multiple sclerosis
- Parkinson’s disease
- Dementia or cognitive decline
- New onset seizures
- Psychiatric illness
- Developmental or behavioral disorders of children
- Chronic cardiomyopathy of unknown cause
† list via Wormser et al
See also the following LymeScience pages:
- How chronic Lyme recruits followers
- Lyme misdiagnosis illustrated
- Red flags of chronic Lyme quackery
- CDC scientist: Why bands 31 and 34 aren’t used to test for Lyme disease
- When do symptoms mean Lyme disease?
- UK warns about inappropriate Lyme disease testing
Other misconceptions about Lyme disease diagnosis and testing are discussed below.
Table excerpted and reformatted*** from the longer 2013 paper (ref 2 below, which is worth reading):
There is substantial evidence supporting the accuracy of FDA-cleared tests once antibodies build up in the body (4-6 weeks post-infection).
The CDC concurs:
You may have heard that the blood test for Lyme disease is correctly positive only 65% of the time or less. This is misleading information. As with serologic tests for other infectious diseases, the accuracy of the test depends upon the stage of disease. During the first few weeks of infection, such as when a patient has an erythema migrans rash, the test is expected to be negative.
Several weeks after infection, currently available ELISA, EIA and IFA tests and two-tier testing have very good sensitivity.
It is possible for someone who was infected with Lyme disease to test negative because:
- Some people who receive antibiotics (e.g., doxycycline) early in disease (within the first few weeks after tick bite) may not develop antibodies or may only develop them at levels too low to be detected by the test.
- Antibodies against Lyme disease bacteria usually take a few weeks to develop, so tests performed before this time may be negative even if the person is infected. In this case, if the person is retested a few weeks later, they should have a positive test if they have Lyme disease. It is not until 4 to 6 weeks have passed that the test is likely to be positive. This does not mean that the test is bad, only that it needs to be used correctly. 
** 99.4% sensitive (95% confidence interval: 95.7–99.9) and 99.3% (95% confidence interval: 98.5-99.7%) specific.
*** LymeScience reformatted the table and added punctuation, emphasis, a note, and changed the word “evidence” to “science”. Excerpted for educational and commentary purposes.
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Updated May 5, 2022