Lyme Disease Tests: Purpose, Test Details & Results

Lyme disease is one of the most commonly reported tick-borne illnesses in North America and Europe. Yet, diagnosing it can be a confusing and stressful journey for patients and physicians alike. Laboratory tests are crucial for confirming Lyme disease, guiding treatment, and providing peace of mind. This article unpacks the purpose of Lyme disease tests, explores the latest testing details, and explains how to interpret results and next steps, all based on current scientific evidence.

Purpose of Lyme Disease Tests

Lyme disease testing is more than just a laboratory checkbox—it's a vital tool that helps clinicians differentiate Lyme disease from other conditions with similar symptoms. Testing also ensures that patients receive appropriate treatment, while avoiding unnecessary antibiotics when Lyme is unlikely. But tests are not perfect, and their role must always be framed within the larger context of a patient’s symptoms and risk factors.

Table 1: Purposes of Lyme Disease Tests

Why Testing Is Needed

Lyme disease can mimic many other illnesses, making clinical diagnosis alone challenging. Testing serves several key purposes:

• Confirming a diagnosis: When a patient presents with suggestive symptoms (like erythema migrans rash, joint pain, or neurological signs) and a reasonable likelihood of exposure, laboratory tests help confirm or rule out infection 2 5 6.
• Supporting treatment decisions: Accurate diagnosis ensures that antibiotics are prescribed to those who need them, and withheld from those who don’t, minimizing unnecessary medication and antibiotic resistance 2 6.
• Surveillance and epidemiology: Testing data helps public health authorities monitor Lyme disease trends and respond to outbreaks 6 9.
• Patient reassurance: For patients with low risk but high concern, negative testing can provide reassurance and prevent unnecessary treatments 2 10.

Clinical Judgment Remains Essential

It’s important to remember that no test is perfect. The value of a Lyme disease test depends greatly on the pre-test probability—which is how likely a patient has Lyme disease before testing, based on symptoms, tick exposure, and geography. Testing is most useful when the likelihood of disease is moderate to high; in low-risk scenarios, false positives may cause confusion and overtreatment 2 10.

Lyme Disease Tests Details

Understanding the different types of Lyme disease tests—and their strengths and limitations—is key for both patients and clinicians. The current standard continues to evolve, with new technologies promising better accuracy.

Table 2: Lyme Disease Test Types and Characteristics

The Two-Tiered Testing Approach

The most widely used diagnostic protocol is the two-tiered serologic testing algorithm:

1. First tier: A sensitive enzyme-linked immunosorbent assay (ELISA) or immunofluorescence assay (IFA) screens for antibodies to Borrelia burgdorferi.
2. Second tier: If the first test is positive or equivocal, a more specific Western blot is used to confirm the result 2 5 6 9 10.

This combination increases specificity—meaning it’s unlikely to give a false positive—but can miss cases early in infection when antibodies have not yet developed 1 2 5 7 9. Sensitivities as low as 50% have been reported in patients with early Lyme disease (e.g., those with an erythema migrans rash), but increase in later stages 7 9.

ELISA and Immunoblot Details

• ELISA is generally used as the screening test. It’s sensitive but can produce false positives, especially in people with other infections or autoimmune conditions 2 7 11.
• Western Blot provides confirmation by detecting antibodies against specific Borrelia proteins. However, interpretation can be challenging, and false positives may occur due to cross-reactivity with other infections (notably viral infections like EBV or CMV) 2 9 11.

Direct Detection Methods

Direct detection methods—such as culturing the bacteria from blood or tissue, or using PCR to find Borrelia DNA—are considered the gold standard for proving active infection. Unfortunately, these are rarely used in clinical practice due to low sensitivity, high cost, and lack of standardization. They are more often used in research or extraordinary clinical circumstances 2 3 4 9.

Advances and Alternative Testing

Recent research has led to the development of new test formats:

• Multiplex bead-based assays: These use a combination of Borrelia antigens to increase the likelihood of detecting antibodies at all disease stages. Some have shown higher sensitivity than standard ELISA or two-tiered tests but may sacrifice specificity 1.
• Novel biomarkers and cytokine assays: Tests like CXCL-13 (for neuroborreliosis) and metabolic profiling are being investigated, but are not widely available or standardized 4 5.
• VlsE antigen-based assays: Use recombinant proteins to improve specificity, particularly in IgG detection, and may help distinguish true infections from vaccine-induced antibodies 8.

Limitations and Challenges

• Window period: Antibodies take time to develop after infection, so very early disease may yield false-negative results 1 2 7 9.
• Cross-reactivity: Other infections (especially viral) and autoimmune diseases can cause false positives due to non-specific antibody responses 11.
• Geographic strains: Some tests may not detect all Borrelia species, especially in regions with diverse strains 2 8.
• Non-validated tests: Many commercial and in-house tests have not undergone rigorous evaluation and may be unreliable 9.

Lyme Disease Tests Results & Follow-Up

Test results for Lyme disease don’t always provide a simple “yes” or “no” answer. Understanding what results mean—and what to do next—is essential for patient care.

Table 3: Lyme Disease Test Results and Clinical Actions

Interpreting Results

• Positive tests: Generally mean the patient has been exposed to Borrelia burgdorferi, but cannot distinguish between current, past, or even reinfection. Clinical context and timing are critical to interpretation 2 9 10.
• Negative tests: If performed early (days after tick bite or symptom onset), may be falsely negative due to the “window period” before antibodies develop. Retesting after a few weeks is recommended if suspicion remains high 1 2 7 9.
• Indeterminate or equivocal results: Not uncommon, especially with Western blot. Repeat testing or additional clinical evaluation is often necessary 2 10.

False Positives and Negatives

• False positives: Can occur due to antibodies from other infections (like EBV, CMV, or BK virus) cross-reacting with Borrelia antigens, or from past Lyme infection. This can lead to unnecessary treatments if not interpreted carefully 11.
• False negatives: Most common in early disease or immunocompromised patients who may not mount a detectable antibody response 1 2 7.

What Happens Next?

If Lyme Disease Is Confirmed

• Begin or continue appropriate antibiotic treatment.
• Monitor for symptom improvement, as antibody levels may remain elevated even after successful treatment 2 9 10.

If Lyme Disease Is Ruled Out

• Reassess symptoms: Consider alternative diagnoses.
• Avoid unnecessary antibiotics, which can lead to side effects and antibiotic resistance 2 10.

If the Result Is Unclear

• Repeat testing after several weeks if clinical suspicion remains high.
• Use clinical judgment: Testing should always be considered alongside symptoms, exposure risk, and epidemiological context 2 10.

Conclusion

Diagnosing Lyme disease is a nuanced process that requires both laboratory evidence and clinical insight. While current tests have improved, they are not perfect, and results must always be interpreted in the context of a patient’s symptoms and risk of exposure.

Key points:

• Testing is most valuable when pre-test probability is moderate to high, based on symptoms and exposure.
• The two-tiered serologic approach (ELISA + Western blot) remains the standard, but has limited sensitivity in early disease and can be affected by cross-reactivity 1 2 5 7 9 10 11.
• Direct detection methods and novel biomarkers are promising but not yet standard 1 3 4 5.
• False positives and false negatives are possible; always use clinical judgment in interpreting results 2 7 9 10 11.
• Patient follow-up should be individualized, with repeat testing or alternative diagnoses considered when appropriate.

By understanding the strengths and limits of Lyme disease tests, patients and providers can make more informed decisions—leading to better care, less anxiety, and improved outcomes.