Novel Molecular Test Detects Lyme Disease Earlier

Lyme disease has increased across the United States over the past three decades, especially in the Northeast, where ticks carrying Borrelia burgdorferi are most active from late spring through early fall. Untreated cases can lead to complications affecting the joints, heart, and nervous system. Yet early detection remains difficult—fewer than one in four patients develop the telltale bull’s-eye rash, and many present with skin lesions resembling other conditions. Traditional antibody tests often fail in early infection, returning false negatives before the immune system produces measurable antibodies.

To address these challenges, a team at Dartmouth Hitchcock Medical Center developed a molecular method that identifies Borrelia burgdorferi directly, offering a faster and more accurate diagnosis. The work, led by Guohong Huang, will be presented at the Association for Molecular Pathology (AMP) 2025 Annual Meeting & Expo in Boston next week.

The development of the new test began after doctors treated a 73-year-old woman whose skin hardened and inflamed over four years, eventually limiting her mobility. Initially diagnosed with morphea, she failed to improve under immunosuppressive therapy. Although antibody testing showed only previous exposure to Lyme disease, her symptoms improved after taking doxycycline, a standard antibiotic for Lyme treatment. This case prompted the patient's care team to ask Huang’s department to create a new molecular diagnostic tool for confirmation.

Huang’s group designed three droplet digital PCR (ddPCR) assays. One detects all Borrelia species, another targets those responsible for Lyme disease, and a third identifies Borrelia burgdorferi specifically. Testing on a small number of confirmed and suspected Lyme samples showed the assays could detect as few as five to ten bacterial cells with high accuracy. The B. burgdorferi-specific test reached 90.9% sensitivity in FFPE tissue, and even higher sensitivity is expected in fresh or frozen samples with better DNA quality. 

“Using the ddPCR assay, we successfully detected B. burgdorferi DNA in this patient’s skin biopsy,” Huang said. “This finding was further confirmed by DNA sequencing, supporting the diagnosis of chronic Lyme disease.” She emphasized that antibody tests cannot separate active infection from past exposure, making the molecular approach valuable because it detects ongoing bacterial presence. Huang and her team plan to expand testing to more cases and enhance assay sensitivity to support earlier, more reliable diagnoses.