Researchers at Dartmouth Hitchcock Medical Center have developed a set of droplet digital polymerase chain reaction (ddPCR) assays that could allow for earlier and more accurate diagnosis of Lyme disease and related tick-borne infections. The new assays detect genetic material from Borrelia species, including Borrelia burgdorferi, the primary causative agent of Lyme disease in the United States, potentially overcoming limitations of conventional antibody testing.

 The project was led by Guohong (Grace) Huang, PhD, of the Laboratory for Clinical Genomics and Advanced Technology at Dartmouth Hitchcock in Lebanon, New Hampshire. The data were presented Friday during a poster session at the 2025 Association for Molecular Pathology annual meeting in Boston.

Huang’s team developed 3 ddPCR assays: one targeting all Borrelia species, one targeting all Borrelia species that cause Lyme disease, and one specific to B. burgdorferi. The assays were validated using both reference strains and clinical samples, including blood and formalin-fixed, paraffin-embedded skin biopsies. Results demonstrated high sensitivity, capable of detecting as few as 5 to 10 bacterial cells, as well as high specificity, avoiding false positives from nontarget organisms.

The research was motivated in part by a clinical case involving a 73-year-old female with chronic skin lesions and joint immobility. Conventional antibody testing indicated only prior exposure to Lyme disease, but the patient responded to doxycycline. Using the ddPCR assay, Huang’s team detected active B. burgdorferi DNA. The findings were later confirmed by sequencing.

By detecting bacterial DNA directly rather than relying on indirect immune markers, the ddPCR approach could shorten the time to diagnosis and allow for more prompt treatment, explained Dr. Huang. This would reduce the risk of long-term complications from Lyme disease.

The team has tested the assays on multiple ddPCR platforms, demonstrating consistent performance across instruments. This could facilitate adoption in clinical laboratories already equipped with standard ddPCR systems, she said. “To advance this work, the next step is to expand testing to a large number of cases and explore strategies to further enhance the assay sensitivity,” concluded Dr. Huang.