A threshold for concern? C-reactive protein levels following operatively managed neck of femur fractures can detect infectious complications with a simple formula

INTRODUCTION: C-reactive protein (CRP) rises in response to multiple stimuli, including surgical procedures and infections. Deviations from the predicted CRP response to a given procedure may be an early indication of a postoperative complication. METHODS: Three hundred and fifty-four patients with an operatively managed neck of femur fracture admitted over a 1-year period to an NHS Hospital Trust were included. CRP values collected during the postoperative period were retrospectively examined, and objective evidence of postoperative complications was sought. Data analysis explored daily CRP thresholds that maximised sensitivity and specificity for the detection of patients with a postoperative complication. RESULTS: From the 5th to the 30th postoperative day, a CRP value in excess of the threshold defined by the formula 500/d (where d represents the number of postoperative days) retrospectively detected patients with a postoperative complication with a sensitivity of 0.97 and specificity of 0.82. Patients with a CRP value above the 500/d threshold during this period had a significantly increased 30-day mortality (10.0% vs. 3.9%, RR=2.74, p=0.03). CONCLUSION: Following operatively managed neck of femur fractures, a CRP value in excess of the threshold defined by the formula 500/d may indicate the presence of a postoperative complication and defines a group with increased mortality. In this context, a prompt wound review and septic screen could promote the early detection and management of infectious postoperative complications.