A Clinical Prediction Rule for Bacterial Musculoskeletal Infections in Children with Monoarthritis in Lyme Endemic Regions

Pediatric musculoskeletal infections

“…Plain radiographs have low sensitivity for septic arthritis, but are frequently performed to evaluate for effusion and rule out other causes [15]. Blood biomarkers [peripheral white blood cell (WBC) count, absolute neutrophil count (ANC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and procalcitonin (PCT)] can aid in stratifying a child's risk of septic arthritis [9,10,15,16 ▪▪ ,17,18 ▪ ,19,20]. Blood biomarkers are often combined with the clinical factors from history and physical examination in clinical decision rules.…”

“…However, Lyme serologies can take days to return results if not performed in-house and Lyme arthritis is often difficult to distinguish from septic arthritis given the overlap in clinical presentation, serum biomarkers, and synovial fluid analyses [11,23,30]. Clinical prediction rules have been developed to aid in differentiating those children with Lyme arthritis from those with septic arthritis [11,16 ▪▪ ,31 ▪ ]. Although a positive Lyme PCR testing from the synovial fluid can confirm the diagnosis, it has low sensitivity and should only be performed in conjunction with a two-tier Lyme serology [22,23,29].…”

“…ESR had previously been the favored screening lab for AHO, recent studies favor CRP because of comparable diagnostic utility and more reflective of status during treatment [39 ▪▪ ,52]; therefore, ESR is no longer routinely recommended in AHO evaluation [39 ▪▪ ], though often included while evaluating for other osteoarticular infections [52]. PCT is increasingly utilized in infectious disease management [16 ▪▪ ]; however, in AHO, it is outperformed by CRP and is more expensive. Blood cultures are positive 40% of the time [42,53].…”

Outpatient Treatment of Lyme Disease

“…Children with a PCT of 0.50 ng/mL and higher, CRP greater than 0.6 mg/dL, and a negative Lyme were not at low risk of MSKI. Those with PCT less than 0.50 mg/mL and either a CRP less than 0.6 mg/dL or a CRP of 0.6 mg/dL or higher with a positive or equivocal Lyme were at low risk for MSKI 10 . The decision to treat for septic arthritis, osteomyelitis, or pyomyositis necessitates IV antibiotics, whereas Lyme arthritis can be treated with oral antibiotics (doxycycline, amoxicillin, or cefuroxime) for 28 days.…”

“…Those with PCT less than 0.50 mg/mL and either a CRP less than 0.6 mg/dL or a CRP of 0.6 mg/dL or higher with a positive or equivocal Lyme were at low risk for MSKI. 10 The decision to treat for septic arthritis, osteomyelitis, or pyomyositis necessitates IVantibiotics, whereas Lyme arthritis can be treated with oral antibiotics (doxycycline, amoxicillin, or cefuroxime) for 28 days. In cases where the diagnosis is not clear, the child can be admitted to the hospital for IV antibiotics and, if cultures are negative but Lyme serology is positive, switched to an oral antibiotic to complete a 28-day course.…”