Lyme disease diagnosis: symptoms show the way
The most important indication of a Lyme disease diagnosis is the typical skin rash at the tick bite site: the “wandering redness” (erythema migrans). It is considered the leading symptom of early Lyme disease and occurs in many patients. For this reason, you should keep an eye on the surrounding skin area for several weeks after a tick bite. It often helps to make a small note in your calendar each week to check on the area again. If you notice any change in the skin, you should see a doctor.
Unfortunately, a tick bite also often goes unnoticed or forgotten. If you or your doctor nevertheless suspect Lyme disease, consider whether there is a fundamental possibility of a tick bite – for example, through frequent walks in the woods, picnics in the meadow, regular forest/garden work or jogging in the summer. Your doctor will ask about this as part of the anamnesis (medical history).
Lyme disease test for antibodies
If Lyme disease is suspected, laboratory tests are necessary for clarification. Various Lyme disease tests are available for this purpose. Many of them focus on specific antibodies against the Lyme disease pathogens (Borrelia). Physicians summarize these antibody tests under the term Borrelia serology.
Antibody detection in the blood
These Lyme disease tests (1st stage: ELISA, 2nd stage: immunoblot) look for specific antibodies against Borrelia in a blood sample from the patient. However, a positive result alone is not sufficient for the diagnosis of Lyme disease. Lyme disease symptoms must also be present. Moreover, both false-negative and false-positive test results are possible.
False negative result
A Lyme disease test for antibodies in the blood can show a Borrelia infection only a few weeks after infection. Only then has the immune system formed specific antibodies against the Borrelia. At the time of the characteristic skin rash (“wandering redness”), the Lyme disease test can therefore still be negative (in about half of the cases).
A Lyme disease test can also be falsely negative in patients who are being treated with immunosuppressants for another disease. Immunosuppressants are drugs that suppress the immune system.
False positive result
The antibody Lyme disease tests may also show false positive results. This is the case, for example, if the patient actually has syphilis (lues). This is because both syphilis and Lyme disease pathogens belong to the screw bacteria (spirochetes). The tests then confuse the pathogens due to their similar structure.
Viral infections with EBV (Pfeiffersches glandular fever), hepatitis or varicella (chickenpox and shingles) as well as some autoimmune diseases can also cause false-positive results.
Positive Lyme disease test alone is not conclusive
A Lyme disease blood test can also still be positive even if an infection occurred a long time ago and has long since been cured – either with the help of the body’s defenses alone or through antibiotic therapy. Borrelia antibodies are then often still detectable in the blood.
A positive Lyme disease blood test may only be interpreted as evidence of Lyme disease in conjunction with typical symptoms and the patient’s history (tick bite).
If there are no typical Lyme disease symptoms or only unspecific complaints such as fatigue, malaise, headache, aching limbs or fever, the physician normally does not perform a Lyme disease test. This is because the test result would have no consequences.
Neuroborreliosis: antibody detection in the CSF
If you suspect neuroborreliosis based on your symptoms and the information from the medical history interview, the doctor will take a sample of the cerebrospinal fluid (cerebrospinal fluid, CSF). This is done in the course of a CSF puncture. In the laboratory, the CSF sample is then tested for antibodies against Borrelia, among other things.
Direct pathogen detection
The detection of specific antibodies is very important for the diagnosis of Lyme disease. In support of this, the Borrelia bacteria can be detected directly in the patient’s sample material – on the one hand by culturing the bacteria, and on the other hand by detecting the Borrelia genome.
Borrelia culture
Here one tries to cultivate the bacteria from the patient’s sample. The sample can, for example, come from the pathologically changed skin or the cerebrospinal fluid (in the case of suspected neuroborreliosis).
If such a Borrelia cultivation from sample material succeeds, it is a sure proof of Lyme disease. However, this procedure is very time-consuming and labor-intensive and is only performed in some specialized laboratories.
Borrelia PCR
Alternatively, the genetic material of the Borrelia bacteria can be detected in the patient samples. Hereditary fragments can be amplified by PCR (polymerase chain reaction) and then detected. This is faster than a Borrelia cultivation. This form of Lyme disease test is initiated by the physician especially if the physician suspects a Lyme disease-related joint inflammation (Lyme arthritis) or neuroborreliosis.
The professional societies do not recommend a (routine) direct pathogen detection from blood or urine!
Borrelia detection in the tick
Some laboratories offer Lyme disease tests for submitted ticks. The detection is usually done by polymerase chain reaction (PCR), which is why it is often referred to as tick PCR for short.
However, a positive test result does not automatically mean that the bacteria have also been transmitted to humans. If an infected tick has sucked blood on a human for less than 24 hours, the probability of Borrelia transmission is very low. Thus, the affected person most likely does not have Lyme disease.
In addition, some laboratories test ticks in general for the genetic material of Borrelia burgdorferi sensu lato: this is a large group of closely related Borrelia genospecies, some of which cause Lyme disease, but others do not – at least according to current knowledge. So, in the case of a positive tick Lyme disease test, the affected tick may only be infected with Borrelia, which does not cause Lyme disease in humans.
Borrelia detection in ticks is not suitable for making therapy decisions.
Non-recommended Lyme disease tests
In addition to the detection of Borrelia in ticks, there are a number of other Lyme disease tests that are not recommended by the professional societies according to current knowledge. In most cases, there is a lack of conclusive scientific studies proving the benefit of the respective tests. These include:
- Lymphocyte transformation test (LTT-Borrelia; it can also be positive in people who have never been in contact with Borrelia)
- Lymphocyte population CD57+/CD3- (similar to LTT)
- Antigen detection from different body fluids (no reliable significance)
- Xenodiagnosis (here, shield tick larvae are allowed to suck blood from presumed Lyme disease infected persons and the larvae are then examined for Borrelia, not proven useful, very costly)
- Light microscopic detection (risk of confusion)
- Visual Contrast Sensitivity Test (gray scale test; measurement of the recognition of gray tones under the assumption that a special Borrelia nerve toxin harms the eye, but not proven)
- Freely available tests (too inaccurate)
Conclusion: Lyme disease diagnosis is difficult
For example, a supposed “wandering redness” may actually be a non-specific reaction of the skin to an insect bite, ringworm (in children) or erysipelas. Neurological symptoms, as they appear in neuroborreliosis, can also occur in TBE (early summer meningoencephalitis), a herniated disc or multiple sclerosis, among others.
This means that Lyme disease is first a suspected clinical diagnosis. The assumption in turn results from the patient’s symptoms and medical history. Positive results of Lyme disease test procedures substantiate the suspicion. If the physician can also rule out other possible causes for the symptoms, the diagnosis of Lyme disease is considered confirmed.
