Episode 568: Lyme Disease Testing Is Failing Patients: Dr. Liz Horn Explains Why (And What Comes Next)

June 27, 2026

Episode 568: Lyme Disease Testing Is Failing Patients: Dr. Liz Horn Explains Why (And What Comes Next)

🎙️ Episode Summary: Lyme Testing Is Failing Early Patients

In this critical episode with special guest co-host Ali Moresco, we sit down with Dr. Liz Horn, Principal Investigator of the Lyme Disease Biobank, to break down her latest research:

👉 Evaluation of standard and modified two-tiered testing algorithms using well-characterized early Lyme disease samples

This study takes a hard look at the current FDA-cleared Lyme testing system — and the findings are clear:

👉 Most early Lyme disease cases are being missed

Dr. Horn explains why this is happening, what it means for patients, and why clinical judgment — not just testing — must guide early diagnosis and treatment.

🔬 The Study at the Center of This Episode

📄 View Dr. Liz Horn’s Research Publications

📊 Study Focus:

Compared Standard Two-Tier Testing (STTT) vs Modified Two-Tier Testing (MTTT)
Used real-world patient samples from early Lyme cases
Evaluated four FDA-cleared diagnostic algorithms
Focused primarily on patients within the first ~3 weeks of symptoms

🚨 Key Finding: Early Lyme Testing Is Deeply Flawed

Only 22–36% of early Lyme cases tested positive
That means 64–78% of cases were missed
Most people with early Lyme disease will test negative

📌 Easy-to-share summary for doctors and patients: New Bay Area Lyme Foundation Study Shows Common FDA-Cleared Lyme Tests Miss 64–78% of Early Cases

🧠 Why These Tests Fail

Current tests detect antibodies, not the bacteria itself
The immune system needs time to produce detectable antibodies
Early infections often test negative because the immune response has not developed yet
The two-tier system adds additional opportunities for false negatives

👉 Core issue: Testing measures the body’s response, not the infection

⏱️ The Critical Timing Problem

Within 1 week of symptoms, tests are almost always negative
Around 2 weeks, detection improves slightly
After 3–4 weeks, sensitivity increases but is still unreliable
Testing does not become fully accurate at any point

👉 Key insight: Testing remains inconsistent even after the early window

🎯 Even “Classic” Lyme Cases Are Missed

Patients with erythema migrans (EM rash) often tested negative
Very few patients present with a classic bullseye rash
A visible rash does not guarantee a positive test result

👉 Key takeaway: You can have Lyme and still test negative

⚠️ Major Issue: Test Inconsistency

The same patient can receive different results depending on the test used
One algorithm may detect Lyme while another misses it
Results depend on timing, immune response, and test design

👉 Result: Testing cannot reliably confirm or rule out Lyme disease

🧍‍♂️ Who Actually Tests Positive?

Patients with more symptoms were more likely to test positive
Longer duration of illness increased likelihood of detection
Stronger immune responses improved test sensitivity

👉 Translation: Testing tends to detect later-stage immune response, not early infection

💊 After Treatment: Testing Becomes Even Less Useful

This study focused on early Lyme within the first ~3 weeks, where testing already performed poorly
At approximately 3 months post-treatment, less than 5% of patients who still had an active infection tested positive
These patients were originally diagnosed with early Lyme and many continued to have symptoms consistent with active or ongoing infection

👉 Why this happens: