Multiplexed high-definition PCR 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 co-infections in children with suspected Lyme disease is unknown, creating clinical uncertainty about the optimal approach to diagnosis.

Methods

We enrolled children aged 1 to 21 years presenting to one of eight 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 high-definition multiplex polymerase chain reaction (HDPCR) panel to identify 9 bacterial or protozoan pathogens associated with human disease. We compared the frequency of tick-borne co-infections 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% CI 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 co-infections in children.

Accuracy of Clinician Suspicion of Lyme Disease in the Emergency Department

BACKGROUND

To make initial management decisions, clinicians must estimate the probability of Lyme disease before diagnostic test results are available. Our objective was to examine the accuracy of clinician suspicion for Lyme disease in children undergoing evaluation for Lyme disease.

METHODS

We assembled a prospective cohort of children aged 1 to 21 years who were evaluated for Lyme disease at 1 of the 5 participating emergency departments. Treating physicians were asked to estimate the probability of Lyme disease (on a 10-point scale). We defined a Lyme disease case as a patient with an erythema migrans lesion or positive 2-tiered serology results in a patient with compatible symptoms. We calculated the area under the curve for the receiver operating curve as a measure of the ability of clinician suspicion to diagnose Lyme disease.

RESULTS

We enrolled 1021 children with a median age of 9 years (interquartile range, 5-13 years). Of these, 238 (23%) had Lyme disease. Clinician suspicion had a minimal ability to discriminate between children with and without Lyme disease: area under the curve, 0.75 (95% confidence interval, 0.71-0.79). Of the 554 children who the treating clinicians thought were unlikely to have Lyme disease (score 1-3), 65 (12%) had Lyme disease, and of the 127 children who the treating clinicians thought were very likely to have Lyme disease (score 8-10), 39 (31%) did not have Lyme disease.

CONCLUSIONS

Because clinician suspicion had only minimal accuracy for the diagnosis of Lyme disease, laboratory confirmation is required to avoid both under- and overdiagnosis.