Dr Edward Raby1, Prof Fiona Wood1, A/Prof Laurens Manning1
1Fiona Stanley Hospital
C-reactive protein (CRP) is a widely used inflammatory biomarker but its utility in burns is complicated by the systemic response to injury. The routine threshold is not appropriate for the diagnosis of infection in burns and so novel approaches to interpretation are required.
Adults admitted with acute burns within the last two years were included. Burns specific data and CRP (mg/L) within 30 days of injury were recorded.
1,042 CRP results were available from 296 patients. Median CRP increased from 4 to 20, 90 and 134 over days of injury 0-3 respectively. Peak CRP occurred on day 4 with a significant separation of peak CRP between TBSA groups; 21, 60, 150 and 303 for <1%, 1-5%, 5-20% and >20% TBSA respectively (Kruskal-Wallis p = 0.0001). Combined antibiotic administration and CRP data within 72 hours of injury was available for only 54 patients. Median CRP was 90 in those that received early antibiotics, 34 in those that did without statistical significance (Wilcoxon rank p = 0.17).
The dynamic changes in CRP are predictable in the acute phase of burn injury so that an adjusted threshold could be determined based on TBSA and time since injury to improve accuracy for diagnosis of infection. A larger sample size is required to define the normal population and then to validate this theoretical approach. As there are rapid changes in CRP during this period analysis of CRP considering rate of change should also be considered.
Ed Raby is a microbiologist and infectious diseases physician who is studying towards a PhD focussing on infection and inflammation following acute burn injury.