Biomarkers for Pediatric Bacterial Musculoskeletal Infections in Lyme Disease–Endemic Regions

OBJECTIVES: Bacterial musculoskeletal infections (MSKIs) are challenging to diagnose because of the clinical overlap with other conditions, including Lyme arthritis. We evaluated the performance of blood biomarkers for the diagnosis of MSKIs in Lyme disease–endemic regions. METHODS: We conducted a secondary analysis of a prospective cohort study of children 1 to 21 years old with monoarthritis presenting to 1 of 8 Pedi Lyme Net emergency departments for evaluation of potential Lyme disease. Our primary outcome was an MSKI, which was defined as septic arthritis, osteomyelitis or pyomyositis. We compared the diagnostic accuracy of routinely available biomarkers (absolute neutrophil count, C-reactive protein, erythrocyte sedimentation rate, and procalcitonin) to white blood cells for the identification of an MSKI using the area under the receiver operating characteristic curve (AUC). RESULTS: We identified 1423 children with monoarthritis, of which 82 (5.8%) had an MSKI, 405 (28.5%) Lyme arthritis, and 936 (65.8%) other inflammatory arthritis. When compared with white blood cell count (AUC, 0.63; 95% confidence interval [CI], 0.55–0.71), C-reactive protein (0.84; 95% CI, 0.80–0.89; P < .05), procalcitonin (0.82; 95% CI, 0.77–0.88; P < .05), and erythrocyte sedimentation rate (0.77; 95% CI, 0.71–0.82; P < .05) had higher AUCs, whereas absolute neutrophil count (0.67; 95% CI, 0.61–0.74; P < .11) had a similar AUC. CONCLUSIONS: Commonly available biomarkers can assist in the initial approach to a potential MSKI in a child. However, no single biomarker has high enough accuracy to be used in isolation, especially in Lyme disease–endemic areas.