Clinician Suspicion for Lyme Disease and Clinical Decision-Making in Children with Monoarthritis.

In this large multi-center cohort of children evaluated for Lyme disease in a Lyme-endemic emergency department, we assessed the diagnostic accuracy of clinician suspicion and subsequent clinical decision-making for children presenting with monoarthritis. Among 1,582 children with monoarthritis evaluated for Lyme disease, 623 (39%) had Lyme arthritis and 32 (2%) had septic arthritis. Overall, 313 (20%) had an invasive joint procedure (arthrocentesis or arthroscopy), 194 (12%) received parenteral antibiotics, and 376 (24%) were hospitalized. Clinician suspicion had moderate discriminative ability for Lyme disease (area under the receiver operating characteristics curve: 0.75, 95% confidence interval: 0.72-0.77). Children with higher clinician suspicion were less likely to receive parenteral antibiotics or to be hospitalized, although invasive procedure rates were similar. Our findings highlight the challenge of clinically distinguishing Lyme from septic arthritis. Better diagnostic tools are needed to improve timely diagnosis and minimize invasive testing among children with monoarthritis in Lyme-endemic regions.