Abstract
Purpose
To evaluate the efficacy of Kocher's criteria to differentiate between transient synovitis and septic arthritis in children.
Methods and results
All children with a presentation of ‘atraumatic limp’ and a proven effusion on hip ultrasound between 2004 and 2009 were included. Patient demographics, details of the clinical presentation and laboratory investigations were documented to identify a response to each of the four variables (Weight bearing status, WCC >12,000 cells/m3, CRP >20mg/L and Temperature >38.5°C). SA was defined based upon culture and microscopy of the operative findings. 311 hips were included within the study. Of these 282 were considered to have transient synovitis. 29 patients met criteria to be classified as SA based upon laboratory assessment of the synovial fluid. The introduction of CRP eliminated the need for a four variable model as the prediction for two variables (CRP and weight bearing status) was of similar efficacy. Treating individuals who were non-weight-bearing and a CRP >20mg/L as SA correctly classified 94.8% individuals, with a sensitivity of 75.9%, specificity of 96.8%, positive predictive value of 71.0%, and negative predictive value of 97.5%. CRP was a significant independent predictor of septic arthritis.
Conclusion
Mathematical models using common variables used in clinical practice are a useful way of considering ‘risk’ in SA. However, whilst such models correctly classify the majority of individuals they are by no means failsafe. Such models are more reliable in excluding SA, than including SA, and therefore a clinician's acumen remains important in identifying SA in those individuals with a single abnormal variable.
