STUDY OBJECTIVE: Children with a bacterial musculoskeletal infection (MSKI) require prompt identification and treatment. In Lyme disease endemic areas, children with an MSKI can present similarly to those with Lyme arthritis. Our goal was to derive a clinical prediction rule to accurately identify children at a low risk for an MSKI.

METHODS: We enrolled children with monoarthritis presenting to 1 of 6 Pedi Lyme Net centers and performed a procalcitonin (PCT) and a first-tier Lyme C6 enzyme immunoassay (EIA) test. Our primary outcome was an MSKI (septic arthritis, osteomyelitis, or pyomyositis). Using recursive partitioning with k-fold cross validation, we derived a clinical prediction rule to identify children at a low risk of an MSKI. We calculated the accuracy of our novel rule in a derivation cohort.

RESULTS: Of the 735 children in the derivation cohort with an available research biosample, 39 (5%) had an MSKI (18 had septic arthritis, 20 had osteomyelitis, and 1 had pyomyositis), 260 (37%) had Lyme arthritis, and 436 (53%) had other inflammatory arthritis. Children with a PCT level of more than or equal to 0.50 ng/mL and those with a C-reactive protein (CRP) level of more than or equal to 0.6 mg/dL with a negative Lyme C6 EIA were classified as not low risk for an MSKI. Of the 451 (61%) children categorized as low risk, none had an MSKI (sensitivity 100%, 95% confidence interval 91.0% to 100%; specificity 74.2%, 95% confidence interval 70.5% to 77.6%).

CONCLUSION: A novel clinical decision rule that includes PCT, CRP, and a first-tier Lyme EIA was highly sensitive for MSKIs. Although broader external validation is required, the application of this rule may safely reduce invasive testing, procedures, and treatment for low risk children.

<p><strong>OBJECTIVE: </strong>To examine the association between electrocardiographic (ECG) evidence of carditis at the time of Lyme disease evaluation and a diagnosis of Lyme disease.</p>

<p><strong>STUDY DESIGN: </strong>We performed an eight-center prospective cohort study of children undergoing emergency department evaluation for Lyme disease limited to those who had an ECG obtained by their treating clinicians. The study cardiologist reviewed all ECGs flagged as abnormal by the study sites to assess for ECG evidence of carditis. We defined Lyme disease with the presence of an erythema migrans lesion or a positive two-tier Lyme disease serology. We used logistic regression to measure the association between Lyme disease and AV block or any ECG evidence of carditis.</p>

<p><strong>RESULTS: </strong>Of the 546 children who had an ECG obtained, 214 (39%) had Lyme disease. Overall, 42 children had ECG evidence of carditis of which 24 had atrioventricular (AV) block (20 first degree). Of the patients with ECG evidence of carditis, only 21 (50%) had any cardiac symptoms. The presence of AV block (odds ratio 4.7, 95% confidence interval 1.8-12.1) and any ECG evidence of carditis (odds ratio 2.3, 95% confidence interval 1.2-4.3) were both associated with diagnosis of Lyme disease.</p>

<p><strong>CONCLUSIONS: </strong>ECG evidence of carditis, especially AV block, was associated with a diagnosis of Lyme disease. ECG evidence of carditis can be used as a diagnostic biomarker for Lyme disease to guide initial management while awaiting Lyme disease test results.</p>

<p>The Lyme PCR is a direct detection test, but has not been rigorously evaluated in children undergoing evaluation for acute Lyme disease. We performed a six-center prospective cohort study of children aged 1 to 21 years undergoing acute evaluation for Lyme disease. For this planned secondary analysis, we limited our cohort to children undergoing evaluation for Lyme disease who had any Lyme PCR test obtained by a treating clinician (blood, synovial fluid, or cerebrospinal fluid). We defined a case of Lyme disease with a positive two-tier Lyme disease serology: a positive or equivocal enzyme immunoassay followed by a positive supplemental immunoblot interpreted using standard criteria. We report the test characteristics of Lyme PCR for the diagnosis of Lyme disease. We identified 124 children of whom 54 (43.5%) had Lyme disease. Overall, 23 had a positive PCR test (sensitivity 41.8%; 95% confidence interval [CI] 29.7-55.0; specificity 100%, 95% CI: 94.2-100). All children with a positive Lyme PCR also had a positive two-tiered Lyme disease serology. The Lyme disease PCR test did not improve the diagnosis of children undergoing evaluation for acute Lyme disease. Given the additional costs of this low utility test, clinicians should not order Lyme PCR testing in the acute care setting.</p>

<p><strong>OBJECTIVES: </strong>In Lyme disease endemic areas, initial management of children with arthritis can be challenging because diagnostic tests take several days to return results, leading to potentially unnecessary invasive procedures. Our objective was to examine the role of the C6 peptide enzyme immunoassay (EIA) test to guide initial management.</p>

<p><strong>METHODS: </strong>We enrolled children with acute arthritis undergoing evaluation for Lyme disease presenting to a participating Pedi Lyme Net emergency department (2015-2019) and performed a C6 EIA test. We defined Lyme arthritis with a positive or equivocal C6 EIA test result followed by a positive supplemental immunoblot result and defined septic arthritis as a positive synovial fluid culture result or a positive blood culture result with synovial fluid pleocytosis. Otherwise, children were considered to have inflammatory arthritis. We report the sensitivity and specificity of the C6 EIA for the diagnosis of Lyme arthritis.</p>

<p><strong>RESULTS: </strong>Of the 911 study patients, 211 children (23.2%) had Lyme arthritis, 11 (1.2%) had septic arthritis, and 689 (75.6%) had other inflammatory arthritis. A positive or equivocal C6 EIA result had a sensitivity of 100% (211 out of 211; 95% confidence interval [CI]: 98.2%-100%) and specificity of 94.2% (661 out of 700; 95% CI: 92.5%-95.9%) for Lyme arthritis. None of the 250 children with a positive or equivocal C6 EIA result had septic arthritis (0%; 95% CI: 0%-1.5%), although 75 children underwent diagnostic arthrocentesis and 27 underwent operative joint washout.</p>

<p><strong>CONCLUSIONS: </strong>In Lyme disease endemic areas, a C6 EIA result could be used to guide initial clinical decision-making, without misclassifying children with septic arthritis.</p>