Multiplex High-Definition Polymerase Chain Reaction Assay for the Diagnosis of Tick-borne Infections in Children.

Background: Ixodes scapularis ticks can carry Borrelia species as well as other pathogens that cause human disease. The frequency of tick-borne infections and coinfections in children with suspected Lyme disease is unknown, creating clinical uncertainty about the optimal approach to diagnosis. Methods: We enrolled children aged 1-21 years presenting to 1 of 8 Pedi Lyme Net emergency departments for evaluation of Lyme disease. We selected cases with serologically or clinically diagnosed Lyme disease (erythema migrans or early neurologic disease) matched by symptoms, age, gender, and center to control subjects without Lyme disease. We tested whole blood samples collected at the time of diagnosis using a multiplex high-definition polymerase chain reaction (HDPCR) panel to identify 9 bacterial or protozoan pathogens associated with human disease. We compared the frequency of tick-borne coinfections in children with Lyme disease to matched controls. Results: Of the 612 selected samples, 594 (97.1%) had an interpretable multiplex HDPCR result. We identified the following non-Borrelia tick-borne infections: Anaplasma phagocytophilum (2), Ehrlichia chaffeensis (1), and Babesia microti (12). Children with Lyme disease were more likely to have another tick-borne pathogen identified than matched controls (15/297 [5.1%] Lyme cases vs 0/297 [0%]; difference, 5.1% [95% confidence interval, 2.7%-8.2%]). Conclusions: Although a substantial minority of children with Lyme disease had another tick-borne pathogen identified, either first-line Lyme disease antibiotics provided adequate treatment or the coinfection was subclinical and did not require specific treatment. Further studies are needed to establish the optimal approach to testing for tick-borne coinfections in children.