Lyme serology in non-endemic countries: Why do we request it and what do we find?

The primary objectives of our research were to analyze Lyme serology results from pediatric patients, identify the clinical reasons for ordering these tests, and assess the clinical relevance of the serology results in the context of Lyme disease.

Our study, conducted at a reference pediatric hospital in a non-endemic region for Lyme disease, included all pediatric patients for whom Lyme serology was requested. ELISA and Western blot results were documented. Presenting complaints and findings at the time of admission were recorded. Diagnostic tests were categorized as first-step tests if conducted during the initial visit. Subsequent tests, sent due to the inability to establish a diagnosis based on the results of the first-line tests, were defined as second and third-step tests, respectively.

219 patients, for whom Lyme serology had been requested for varying reasons, were included in our study. The most prevalent complaints and indications observed in the presentations of patients with serology requests were as follows: headache(24.7%), paresis/paresthesia(14.6%), and painful or blurred vision(13.2%). Serology was primarily requested in the presence of neurological(59.4%) and ocular symptoms(13.2%). 68% of the tests were requisitioned during the initial consultation. Nevertheless, it was discerned that no patient received a diagnosis of Lyme disease.

According to the guidelines, Lyme serology should only be performed when there is a realistic possibility of exposure to infected ticks, particularly in patients who have had untreated erythema migrans or those with a history of a tick bite presenting with unexplained joint or neurological symptoms. Our data, in line with these guidelines, suggests that unnecessary Lyme serology testing in non-endemic areas, where exposure is highly unlikely, may lead to false-positive results and unnecessary follow-up testing, as illustrated by the high rate of false-positive ELISAs in our cohort.