Value of C-Reactive Protein in the Assessment of Organ-Space Surgical Site Infections after Elective Open and Laparoscopic Colorectal Surgery

Background: Although C-reactive protein (CRP) has proved useful in the assessment of post-operative infections, its value at those time points useful to assess organ-space surgical site infection (OSI) after open and laparoscopic colorectal surgery has not been clarified. Methods: We compared values of CRP on post-operative days two and five and percentage of change between those days (Delta%D2-5) in patients with and without OSI, after open (OPEN) and laparoscopic (LAP) colo-rectal surgery. Receiver-operating characteristic analysis was performed and indices of test performance of sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, and likelihood ratios (LR+ and LR-) were assessed. Results: The best CRP predictive values for OSI were D5 > 120 mg/L (area under the curve [AUC] 0.959; 95% confidence interval [CI] 0.890-0.990) and Delta%D2-5 < 40% (AUC 0.968; 95% CI 0.901-0.994; p = 0.0001) in OPEN and D5 > 66 mg/L (AUC 0.921; 95% CI 0.841-0.969) and Delta%D2-5 < 48% (AUC 0.894-95% CI 0.806-0.952; p = 0.0001) in LAP. The best measure was NPV (100%; CI 93.6%-100% for D5 and D%D2-5 in OPEN and 98.4%, CI 91.3%-99.7% for D5 and 100%, CI 93.4%-100% for Delta%D2-5 in LAP). Conclusions: In patients with CRP < 120.66 mg/L on post-operative day 5 or a decay from post-operative day two to five of > 40%-48% in OPEN and LAP, respectively, OSI may be ruled out and the patient discharged safely. Careful workup is needed in those patients with higher postoperative CRP concentrations or lower apparent decay values.