Establishing the diagnosis of an infectious disease is not always easy. The essence of it is to identify the agent causing the disease in the patient, whether it be a virus, bacteria, fungus, or parasite. Unfortunately, this presence is not always easy to detect.
In the case of Lyme disease, which is linked to the Borrelia burgdorferi bacteria transmitted by ticks, such detection is even more exceptional. The diagnosis is based on a combination of epidemiological (exposure to tick bites), clinical (skin, joint, neurological symptoms), and biological (blood tests, lumbar or joint punctures) criteria. However, with more or less certainty, not only because many symptoms are not specific, but also because other factors, such as cognitive biases, can disrupt the diagnostic process. Here’s why.
A Bacteria
The B. burgdorferi bacteria is not easy to detect in patients who may have been infected for several reasons:
– It is present in very low numbers in the human body;
– It is found in tissues that are difficult to access, such as the nervous system, joints;
– In the laboratory, it is very difficult to cultivate: its growth is slow and tedious.
The diagnosis of Lyme disease can only be based on indirect evidence. However, taken individually, these elements each have little diagnostic value.
Difficult Symptoms to Identify
During the early phase of Lyme disease, a red spot may appear at the site of the tick bite, which spreads out centrifugally over several weeks. This «erythema migrans» is very specific and does not suggest many other diagnoses.
Unfortunately, it is not always present. The bite can go unnoticed, and patients may present directly with characteristic joint or neurological symptoms of the later phases.
Some of these subjective symptoms are difficult to identify, leading to a questioning of the patient’s health status and a potential breakdown of trust between the doctor and the patient. This breakdown, a source of anxiety, can be further exacerbated by other factors.
Questionnaires, Tools to Handle with Care
In the absence of a medically confirmed diagnosis, patients may embark on a personal diagnostic journey influenced by their readings or surroundings, attributing their symptoms to a specific cause. This includes using questionnaires to test the hypothesis of having Lyme disease, such as the Horowitz Lyme-MSIDS questionnaire. However, the lack of specificity of the symptoms makes it impossible to analyze them according to the usual diagnostic approach in medicine.
Such a process can lead to a misattribution of symptoms to Lyme disease, further eroding the trust between doctor and patient.
Other disruptive elements can increase the complexity of establishing a diagnosis. This includes cognitive biases related to the fear of ticks.
Disturbing Elements Affecting Diagnosis
The fear of ticks is rooted in real facts, but their overinterpretation can increase anxiety. Among these elements are:
– Ticks host numerous microorganisms, and while this makes them dangerous, not all the microbes they carry pose a risk to humans. Moreover, those that do mainly cause benign infections. Additionally, not all tick bites lead to disease transmission. In the case of Lyme, the transmission of the bacteria occurs in less than 5% of cases;
– The insidious nature of Lyme disease: the tick’s blood meal, which lasts several days, is generally painless and can go unnoticed. Similarly, Lyme disease symptoms can appear long after the initial infection (up to several years). This knowledge prevents some people from moving on from their tick bite. Even years later, they continue to fear suffering from its effects, interpreting any subsequent symptom as related to the bite, even if it is not due to Lyme disease.
When such a «confirmation bias» sets in, medical reasoning can be distorted, with the person focusing on elements that align with their perspective.
These cognitive deviations are exacerbated by the recognition by the High Health Authority of the existence of a condition known as «post-tick bite syndrome» without scientific basis. This recognition was denounced by all scientific societies involved in tick-borne disease management.
Another problematic point is the inability to objectify the disease through biology, despite its increasing importance in the field of infectious diseases.
The Role of Biological Analyses
Biological analyses identify anomalies that serve as «evidence» to reveal the cause of a disease. PCR tests during the Covid-19 pandemic are a well-known example of this. However, such analyses have limitations.
In France, the only biological test available for Lyme disease is based on serological analysis. This test does not directly detect the B. burgdorferi bacteria but the antibodies produced during exposure to it. This poses several problems.
Firstly, antibodies appear after varying durations. Their diagnostic value during the early stages of an infectious disease is limited (a «negative serology» cannot rule out the disease). Additionally, antibodies persist even after the elimination of the causal microorganism (sometimes for several years, or even a lifetime).
Their role is to maintain immune memory, mobilized upon reencounter with the same microbe to neutralize it quickly. A «positive serology» does not indicate the presence of the bacteria or that the patient is «sick.»
The interpretation of serological test results follows a process of «confirming» an initial hypothesis. This approach, where the biological examination plays a «secondary» role, is often misunderstood. For some patients, it may be difficult to understand why a «positive» test is not enough to confirm the diagnosis.
Due to its limitations, serology has faced criticism. However, these critiques are often unfounded, as regardless of the infection being sought, serology can only provide information on the presence or absence of specific antibodies, without confirming the presence of the microorganism.
New biological identification techniques for the disease are desired but have not undergone clinical validation. Despite this, some unscrupulous laboratories offer them to patients desperately seeking confirmation of their fears.
Unproven New Tests
In the absence of a definitive diagnosis, some suffering patients seek to confirm their belief in having Lyme disease by undergoing numerous biological tests that they trust more than the doctor.
New tests are proposed to confirm the diagnosis of Lyme disease, especially by laboratories in foreign countries like Germany. These tests, costly and borne by the patient, have either not been clinically evaluated in humans or have shown diagnostic qualities inferior to serology.
Using such tests can often be the point of no return, definitively distancing patients from evidence-based medicine. They see these tests as the ultimate proof confirming their intuition, giving meaning to their fight to have their disease recognized against a medical system that rejects the diagnosis. This raises questions about treatment, where abuses also exist.
Antibiotics and «Therapeutic Test»
In emergencies, infectious disease specialists may resort to an approach based on a «therapeutic test.» This involves initiating treatment without a confirmed diagnosis (known as empirical treatment).
This approach balances the potential benefits of therapy against the risks of not treating the patient while awaiting a diagnosis. It also considers the potential risks of adverse effects.
In practice, the more life-threatening a disease, the more tolerance there is for significant side effects (if the treatment is effective). Meningitis is a typical example: even if the responsible bacteria is unidentified, administering a massive dose of antibiotics early on is crucial to prevent a potentially fatal outcome.
However, Lyme disease does not exhibit these urgent criteria. Physicians have enough time to refine the diagnostic process to consider therapeutic testing only after careful consideration. Nevertheless, in reality, things often play out differently.
Antibiotics without a Diagnosis
In the absence of a confirmed diagnosis, a doctor may still prescribe antibiotics to eliminate a hypothetical B. burgdorferi infection.
The idea is that if symptoms disappear after antibiotic therapy, the diagnosis of a bacterial infection (responsive to antibiotics) will be confirmed retroactively. However, this reasoning and the resulting «default diagnostic» approach are subject to various biases.
This approach does not consider the possibility of symptoms improving spontaneously (unrelated to antibiotics), a placebo effect, or treatment effects of a different nature (which may interfere with symptoms: inflammation processes, pain pathways, microbiome effects…).
Despite the absence of scientific evidence, some doctors justify continuing prolonged antibiotic treatment, which can last for several months. However, there is no widespread evaluation of the actual risks of such treatments. Individually, antibiotics are never without adverse effects (especially digestive, and sometimes neurological, which can exacerbate the initial symptoms of Lyme disease).
This type of prescription further entrenches the belief of already psychologically vulnerable patients in being infected by a bacterium causing their suffering, even though scientific evidence is lacking. Dependent on treatment, they reject any idea of stopping it.
At the extreme, this process can lead some individuals to reject standard healthcare systems, isolating themselves and only listening to those who confirm their false diagnostic construction.
What to Do in Case of Tick Bite or Suspicion?
In cases of suspected Lyme disease, the High Health Authority’s care pathway guide outlines the course of action.
The treating physician should initially guide the patient based on both clinical and, if necessary, biological diagnostic criteria. In case of difficulty, they can refer the patient to a disease specialist by contacting a dedicated competence or reference center. These centers, established in 2019, are available throughout the country.