Evaluation of a novel multiplex high-definition PCR (HDPCR) assay for the detection of tickborne pathogens in whole blood specimens

The prevalence of tickborne infections has been steadily increasing in both number and geographic distribution in the United States and abroad. This increase, in conjunction with the continued recognition of novel pathogens transmitted by ticks, has made accurate diagnosis of these infections challenging. Mainstay serologic tests are insensitive during the acute phase of infection and are often cross-reactive with similar pathogenic and non-pathogenic organisms. Further, they are unable to reliably differentiate active versus past infection which can lead to misdiagnosis and incorrect understanding of the epidemiology and incidence of specific tickborne pathogens. We evaluated a novel multiplexed high-definition PCR (HDPCR) Tickborne Panel (TBP) assay (ChromaCode, Carlsbad, CA) for the detection of 9 tickborne pathogens or groups associated with human illness. The HDPCR technology enables multiplex identification of multiple targets in a single fluorometric channel based on fluorescent signal modulation using a limiting probe design. A collection of 530 whole blood specimens collected from patients being evaluated for tickborne infections in addition to a panel of 93 simulated specimens were used to challenge the HDPCR TBP. Results were compared to a clinically validated traditional multiplexed PCR test with additional sequence analysis and clinical history collected to aid in resolving discrepancies. Among clinical specimens the TBP demonstrated 100% sensitivity for the identification of Anaplasma phagocytophilum, Borrelia miyamotoi, Borrelia mayonii, and Rickettsia rickettsii. The sensitivity for identification of B. burgdorferi was 44.4% when compared to a composite gold standard. Among simulated specimens containing single or multiple targets present at 103-105 copies/PCR reaction, the sensitivity of TBP was 100% for all targets with a combined specificity of 99.5%. Of note, an increased rate of false positive results was observed among simulated specimens that contained multiple targets. Based on these data, we find the HDPCR TBP to be a useful adjunct for the diagnosis of tickborne infections in patients with suspected tickborne illness.