Acute monoarthritis in children: clinical and laboratory factors distinguishing septic arthritis from noninfectious inflammatory arthritis

Ö. Bayrak Demirel, M. Demirel, R.N. Ömeroğlu, S. Hançerli Törün, F. Bilgili, A. Kılıç

Istanbul University, Institute of Child Health, Istanbul, Turkey. dr88.mehmet.demirel@gmail.com

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• Orthopedics

OBJECTIVE: Distinguishing septic arthritis from specific inflammatory arthritis in children with acute monoarthritis can be a clinical challenge. This study aimed to assess the diagnostic performance of presenting clinical and laboratory findings for distinguishing septic arthritis from common forms of noninfectious inflammatory arthritis in children with acute monoarthritis.

PATIENTS AND METHODS: Children presented for the first episode of monoarthritis were retrospectively reviewed and then divided into two groups: (1) the septic group, 57 children with true septic arthritis, and (2) the non-septic group, 60 children with several types of noninfectious inflammatory arthritis. Several clinical findings and serum inflammatory markers on admission were documented.

RESULTS: Univariate analyses demonstrated that body temperature, weight-bearing status, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood cell count (WCC), absolute neutrophil count (ANC), and neutrophil percentage (NP) levels were significantly higher in the septic group than in the non-septic group (p<0.001 for each variable). Based on the ROC analysis, optimum diagnostic cut-off values were 63 mg/L for CRP, 6,300/mm3 for ANC, 53 mm/h for ESR, 65% for NP, 37.1°C for body temperature, and 12,100/mm3 for WCC. While children with no presenting factor had a 4.3% risk of having septic arthritis, those with six predictors had a risk of 96.2%.

CONCLUSIONS: A CRP level of ≥63 mg/L is the best independent predictor of septic arthritis among the commonly used serum inflammatory markers (ESR, WCC, ANP, NP). It should be borne in mind that a child with zero predictors may still have a 4.3% risk of septic arthritis. Thus, clinical assessment is still imperative in managing children presenting with acute mono-arthritis.

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