Abstract
Background:
Early diagnosis of septic arthritis and osteomyelitis in children is essential to prevent long term sequelae. The diagnosis for these orthopaedic emergencies can be difficult and challenging especially in infants. Standard blood tests used for diagnosis have a low specificity. Procalcitonin (PCT) is significantly elevated in bacterial infections and remains low in viral infections and inflammatory conditions. Good positive predictive values for PCT have been obtained in various studies used in paediatric infections, but limited studies have examined the role in orthopaedic infections.
Aims:
To introduce PCT testing in the work up of Septic Arthritis (SA) and Acute Osteomyelitis (OM) and to see if the test is useful in the diagnosis. Also to determine whether 0.2 ng/ml is a suitable cutoff level as indicated by previous studies.
Method:
All children under 14 years presenting with signs and symptoms of SA/OM from 1 June 2009 to 31 June 2010 were subjected to standard blood tests with addition of PCT and compared to a control group. The definitive diagnosis was made by microbiologic examination obtained in theatre. A PCT cut-off level of 0.2 ng/mL was used.
Results:
A total number of 33 patients were included in the study. Eight patients were diagnosed as OM, 4 as SA and 21 had another diagnosis. Staphylococcus aureus was the most common organism isolated in this series with no resistant organisms seen.
In the SA/OM Group 11 of the 12 patients had an increased PCT level and 4 in the other diagnosis group had raised PCT. The calculated sensitivity of PCT was 92% with a confidence interval of 62–100% and the specificity was 81% with a confidence interval of 58–95%. In this study the sensitivity of CRP was 100% while the specificity 26%. The positive predictive value for PCT in this study was 73% and the negative predictive value was 94%. The accuracy for PCT in Septic Arthritis and Osteomyelitis in this study was 85%.
Conclusions:
The calculated sensitivity and specificity in this study has shown that PCT testing can aid in the diagnosis of SA/OM in children using 0.2 ng/ml as cut-off level. PCT was more specific for bacterial infections in this study than CRP. Further research is needed with larger numbers to conclusively prove that this specific cut-off for PCT is significant.
