THE USEFULNESS OF C REACTIVE PROTEIN AND ERYTHROCYTE SEDIMENTATION RATE IN DIAGNOSING LONG BONE OSTEOMYELITIS IN CHILDREN – ARE WE BEING FALSELY REASSURED?

Purpose To assess the initial rise in inflammatory markers in paediatric patients presenting with long bone osteomyelitis and whether this is comparable with that in septic arthritis, and diagnostic. Methods All radiologically confirmed cases of long bone osteomyelitis without septic arthritis, joint effusion or abscess, in paediatric patients, presenting to one hospital over an eighteen-month period were included. These patients were compared with all culture positive septic arthritides presenting to the same hospital within the same period. Inflammatory markers taken on the day of admission were studied. Results Thirty-seven patients with osteomyelitis and thirteen with culture positive septic arthritis were identified. The two groups were comparable with regards to age and gender. At presentation 65% of the osteomyelitis patients had an ESR, (erythrocyte sedimentation rate), less than 40mm/hour, 48% below 20mm/hour and 19% within the normal range. 23% of the septic arthritis patients had an ESR below 40mm/hour, and none had an ESR below 20mm/hour or in the normal range. The CRP, (C reactive protein), was in the normal range in 46% of the osteomyelitis patients and none of the septic arthritis patients. The average ESR and CRP in the osteomyelitis patients were 47mm/hour and 35mg/L respectively, while in the septic arthritis group these were 72mm/hour and 107mg/L, (P Conclusion The initial rise in inflammatory markers due to long bone osteomyelitis is significantly less than that in septic arthritis. A proportion of patients with osteomyelitis have normal inflammatory markers at presentation. A high index of suspicion is required, and inflammatory markers, while a useful adjunct to monitoring treatment, may offer false reassurance regarding the initial diagnosis.