NRL News

Edition 2, 2019

NRL News

Performance of Serological Assays Used for Lyme Disease Testing in Australia

 

Lyme Disease (LD) caused by the spirochaetes Borrelia burgdorferi is transmitted to humans by infected ticks and is known to be prevalent in parts of Europe, North America and North Asia. LD causes a variety of symptoms that can proceed through 3 distinct stages and be very debilitating. Rash, fever and flu-like symptoms are experienced in the early localised stage, which is followed by headaches, severe fatigue, pain and swelling in joints and lymph glands in the early disseminated stage. According to CDC approximately 60% of patients with untreated LD infection will further progress to the late disseminated stage experiencing intermittent bouts of arthritis with severe joint pain and swelling. Further, some of these individuals will develop severe chronic neurological complaints months to years after infection.

Lyme Disease has not been identified in Australia despite the existence of Australia patients who have never been overseas experiencing symptoms consistent with “chronic Lyme Disease”. Testing of these patients in Australia and overseas laboratories has sometimes yielded conflicting results in identifying the causative agent as B.burgdorferi. Affected patients have questioned the validity of results from Australian laboratories and sought assistance from the Australian government to clarify such discrepancies. The significant controversy as to whether LD can be acquired locally in Australia led to a Senate inquiry commencing in November 2015: The growing evidence of an emerging tick-borne disease that causes a Lyme Disease‑like illness for many Australian patients.

The Australian Government Department of Health contracted NRL to undertake an investigation to examine the performance of a range of different serological assays used to detect B.burgdorferi antibodies in specimens collected from Australian individuals. This full study entitled: Investigation of the performance of serological assays used for Lyme disease testing in Australia authored by Drs Susan Best, Kim Wilson and Marlene Tschaepe of NRL, has recently been published in PLOS ONE 9. They found that when using the same assay, discordance between study and clinical laboratories’ results occurred less than 2% of the time and that the assays agreed on positive results approximately 80% of the time and on negative results approximately 90% of the time. These findings suggest that discordance in results between laboratories is most likely due to variation in algorithms or in different assays’ sensitivities or specificities rather than different results being reported from the same assay between laboratories. In the known negative population, specificities of the immunoassays ranged between 87.7% and 99.7%. In Australia’s low prevalence population, this would translate to a positive predictive value of <4%.

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