Lyme disease diagnosis: waiting for the next gold standard

Lyme disease is caused by Borrelia spirochaetes: predominantly Borrelia burgdorferi in North America (but also present in Europe), and predominantly B. afzelii and B. garinii in Europe and Asia and is spread to people via infected deer ticks. Infection occurs after only a minority of tick bites, but is typified by three stages. Stage 1, early localized lyme disease is characterized by the bull’s eye rash (erythema migrans (EM)). Stage 2, early disseminated infection occurs within days to weeks after the local infection as the bacteria begin to spread through the bloodstream. Stage 3, late disseminated infection, where the infection has spread throughout the body, can occur several months later in untreated or inadequately treated patients involving chronic symptoms that can be severe and disabling. Treatment by antibiotics is effective in the early localized stage of the disease but this is often hampered by late diagnosis. Diagnosis can be delayed for a number of reasons: there is a lack of awareness in the general public (as well as GPs outside of what are thought to be the high-risk areas); approximately 25% of people do not get the typical bull’s eye rash; and symptoms can be so varied and vague that, when occurring weeks or months later, are difficult to relate back to the time of the tick bite. Knowledge of a tick bite and an associated EM rash is sufficient for diagnosis. However, in cases where there is a clinical suspicion of Lyme disease but no EM rash, laboratory testing is advised. Testing for antibodies is done via a two-tiered approach, starting with a sensitive ELISA, which, if positive or equivocal, is followed by a more specific immunoblot. However, the overall sensitivity of the two-tiered tests is only 64% when done in the early stages of infection, which is when accurate diagnosis is most needed. Because of these diagnostic limitations, the prevalence of Lyme disease is likely to be far higher than is currently thought. With increasing incidence and geographic spread of the disease, better testing for diagnosis, particularly in the early stages of infection, is perhaps required. Research is ongoing into PCR methods as well as and for the detection of OspA antigens that are shed into urine. An LLT-MELISA (lymphocyte transformation test-memory lymphocyte immunostimulation assay) has been developed and is suggested to be a useful supportive diagnostic tool, particularly in infections acquired in Europe. In the USA, next-generation sequencing (NGS) has been used for specific pathogen identification and to guide treatment decisions. With technological advances making NGS quicker and cheaper, could this eventually become the next gold standard test for Lyme disease?