Lyme Disease Testing Gap: 82% Untested in Non-Endemic Regions

Most patients with symptoms consistent with Lyme disease are not tested in non-endemic regions—creating a major diagnostic gap.

The Testing Gap in Non-Endemic Regions

Researchers from Duke University Health System in North Carolina reviewed the medical records of 1,621 patients with a clinical history consistent with Lyme disease who sought care between 2005 and 2010. The findings highlight a striking pattern in Lyme disease testing in non-endemic regions.

Only 297 patients (18%) of the 1,621 individuals were tested for Lyme disease. This means that 82% of patients with documented clinical histories consistent with Lyme disease were never tested. :contentReference[oaicite:0]{index=0}

These were not vague complaints—these were patients whose symptoms warranted consideration of Lyme disease, yet most never underwent diagnostic evaluation.

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Who Was Tested—and Who Wasn’t

The 297 patients who were tested had classic, late-stage Lyme disease presentations:

• 110 patients with large joint arthritis
• 98 patients with cranial nerve palsy
• 75 patients with meningitis
• 11 patients with both meningitis and cranial neuropathy
• 1 patient with arthritis plus cranial nerve palsy
• 1 patient with atrioventricular block alone
• 1 patient with atrioventricular block plus cranial nerve palsy

These are well-recognized Lyme disease manifestations. Large joint arthritis, facial nerve palsy, meningitis, and cardiac conduction abnormalities are textbook presentations.

Yet even among these classic cases, only a minority were tested.

This pattern reflects geographic bias. In endemic regions, clinicians often test broadly. In non-endemic regions, testing is limited to only the most obvious cases—and even then, inconsistently.

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The Narrow Focus Problem

The study focused only on conditions most frequently associated with Lyme disease and excluded many well-documented manifestations, including:

• Chronic neurologic Lyme disease
• Lyme encephalopathy
• Neuropsychiatric Lyme disease
• Post-treatment Lyme disease syndrome

These conditions are described extensively in the medical literature but were not included because they were not considered for testing in this setting.

While 82% of classic presentations were not tested, the rate for atypical presentations is likely even higher.

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Why Were 82% Not Tested?

The study did not examine why most patients were not tested. However, several likely factors contribute:

• Geographic bias—North Carolina is not widely considered endemic
• Lack of clinician awareness of Lyme presentations
• Alternative diagnoses pursued instead
• Reluctance to order testing for perceived low-risk conditions
• Symptoms attributed to stress or non-medical causes

These factors create systemic barriers to diagnosis in non-endemic regions.

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Consequences of Testing Delays

Delays in Lyme disease diagnosis have been well documented.

Treatment delays averaging 1.8 to 2 years have been reported in case series and studies of Lyme encephalopathy.

In one analysis, 60% of patients with delayed diagnosis had classic CDC-defined presentations, including:

• Erythema migrans rash
• Bell’s palsy
• Lyme arthritis

These were not atypical cases—they were textbook presentations that should have triggered immediate evaluation.

During these delays, patients may progress to more advanced disease, including neurologic and systemic complications.

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Geographic Expansion Matters

Lyme disease is no longer confined to traditionally endemic areas.

Tick populations are expanding due to climate change, migratory birds, and changes in land use.

North Carolina now has confirmed endemic counties, and neighboring states have documented increasing incidence.

Clinical practice has not kept pace with this geographic expansion.

As a result, patients in emerging regions may go undiagnosed because clinicians rely on outdated assumptions about where Lyme disease occurs.

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Frequently Asked Questions

How many patients were tested for Lyme disease?
Only 18% (297 of 1,621 patients) were tested. The remaining 82% received no testing despite having symptoms consistent with Lyme disease.

What symptoms triggered testing?
Testing was primarily limited to classic late-stage presentations such as arthritis, cranial nerve palsy, meningitis, and cardiac abnormalities.

Why were most patients not tested?
Likely reasons include geographic bias, lack of awareness, alternative diagnoses, and underestimation of Lyme disease risk.

How long are diagnosis delays?
On average, 1.8 to 2 years. Many patients with classic symptoms experienced prolonged delays before diagnosis.

Should Lyme disease be considered in non-endemic areas?
Yes. Lyme disease is expanding geographically, and testing should be based on clinical presentation rather than location alone.

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Clinical Takeaway

This study reveals a major Lyme disease testing gap in non-endemic regions. Of 1,621 patients with clinical histories consistent with Lyme disease, only 18% were tested. The remaining 82% received no diagnostic evaluation despite symptoms warranting investigation. :contentReference[oaicite:1]{index=1}

The patients who were tested had classic Lyme presentations:

• Large joint arthritis
• Cranial nerve palsy (Bell’s palsy)
• Meningitis
• Cardiac conduction abnormalities

Even among these textbook cases, testing occurred in only a minority of patients.

The study excluded more complex presentations, including neurologic and psychiatric manifestations, where testing rates are likely even lower.

Why This Matters

• Geographic bias leads to missed diagnoses
• Patients with clear symptoms are not evaluated
• Diagnosis is delayed by up to 2 years
• Disease may progress to chronic complications

Clinicians should evaluate patients with symptoms consistent with Lyme disease regardless of geographic location.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention