Diagnostic value of C-reactive-protein and transthyretin in infection after open fractures of the lower limb (preliminary study)

Purpose of the study The authors investigated the value of C-reactive prote in (CRP) and transthyretin (TTR) in the early diagnosis of infection after open fractures of the lower limb in an open, prospective study. Material and methods Eighty patients were treated with acute debridement an d bone fixation. Follow-up included clinical, radiological, bacteriological and biological assessment: white cell blood count (WBC), erythrocyte sedim entation rate (ESR), CRP and TTR. Diagnosis of infection was based on macro scopic presence of pus. Results Post-operative reference biological profiles were defined in 74 cas es without infection. Reference profiles of WBC and ESR showed unreliable i nterindividual variations and could not be considered for the diagnosis of infection. Reference profiles of CRP and TTR showed a respective increase ( for CRP) and decrease (for TTR) in the early post-operative course, with re turn to normal values after 12 days. In 6 infected patients, CRP concentrat ions were suddenly increased and TTR concentrations decreased at the time ( 3 cases) or even before (3 cases) clinical diagnosis of infection. These va riations were mostly simultaneous. No unusual profile was found. The ratio of CRP/TTR concentrations experienced also a sudden increase in infected ca ses. Discussion Because of unspecifical and unreliable variations in the post-op erative outcome of non infected patients, WBC and ESR cannot be considered for the early diagnosis of infection. CRP and TTR concentrations with a res pective cut-off value of 100 mg/L and 120 mg/L were found efficient for the early diagnosis of infection, and preceeded Clinical diagnosis in three of them. A CRP/TTR ratio over 60 p. 100, 8 days or more after initial surgery was found to be very specific (93 p. 100) and sensitive (100 p. 100) for t he diagnosis of infection. Conclusion Serial quantifications of CRP and TTR should be performed every four days during the follow-up of open fractures in order to early diagnose a post-operative infection. Comparison of both CRP and TTR could allow a h igher accuracy, because of the possible lack of variation of one of the two markers.