Is procalcitonin useful in diagnosing septic arthritis and osteomyelitis in children?

Abstract

BACKGROUND: Early diagnosis of septic arthritis (SA) and osteomyelitis (OM) 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. METHOD: All children under 14 years of age presenting with signs and symptoms of SA or OM from 1 June 2009 to 31 June 2010 were subjected to standard blood tests with the addition of PCT. The definitive diagnosis was made by clinical, surgical and microbiologic data obtained. A cut-off level of 0.2 ng/mL was used. RESULTS: Thirty-three patients were included from which 12 were subdivided into the SA/OM group and 21 into an Other diagnosis group which acted as a control. Of the 12 patients in the SA/OM group, eight patients were diagnosed with SA and four with OM. In the SA/OM group, 11 from 12 patients had an increased PCT level compared to four in the Other diagnosis group. The calculated sensitivity of PCT was 92% with a confidence interval of 62-100%; 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 SA and OM in this study was 85%. CONCLUSIONS: The calculated sensitivity and specificity in this study has proved that PCT testing can aid in the diagnosis of SA/OM in children by using 0.2 ng/mL as cut-off level. PCT is also more specific for bacterial infections in this study compared to CRP. Staphylococcus aureus is the most common organism isolated in this series with no resistant organisms seen. Further research is needed with larger numbers to conclusively prove that this specific cut-off for PCT is significant.