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An investigational polymerase chain reaction (PCR) test that detects the presence of a viral gene in Lyme disease–causing bacteria can distinguish between early and late infection, according to the results of a study that the authors describe as "systematic and comprehensive."

"The current way of diagnosing Lyme disease is struggling to reflect the 'true' incidence of Lyme disease," study investigator Jinyu Shan, PhD, said in an interview with Medscape Medical News. Although there are tests for Lyme disease approved by the US Food and Drug Administration, they are based on the development of antibodies in the blood, and the problem is that antibodies might not develop until several weeks after an infection.

Diagnosis therefore still relies heavily on the clinician's experience. There are often tell-tale signs — such as a 'bullseye' skin rash or having been to an area known to be infested with ticks that carry Lyme disease — but this might not always be the case.

For the new test, "we're not targeting bacteria. We're targeting bacteriophages," said Shan, a research fellow in the Department of Genetics and Genome Biology at the University of Leicester, United Kingdom.

Fortunately, there's high correlation between the presence of the bacteriophage terminase large subunit (terL) gene and the presence Borrelia burgdorferi, the spirochete that causes Lyme disease. "If you find the bacteriophages, the bacteria are there," said Shan.

Importantly, there are ten times more bacteriophages compared to the bacteria, so you have a lot more targets," he added.

Although the novel test still needs evaluation in a clinical trial, it could represent a "step-change" in the detection of Lyme disease, Shan and associates suggest in their report published in Frontiers in Microbiology.