Comparison of C-reactive protein and procalcitonin as predictors of postoperative infectious complications after elective colorectal surgery

Abstract

Aim: To assess diagnostic value of perioperative procalcitonin (PCT) levels compared to C-reactive protein (CRP) levels in early detection of infectious complications following colorectal surgery.

Methods: This prospective observational study included 79 patients undergoing elective colorectal surgery. White blood cell count, CRP, and PCT were measured preoperatively and on postoperative days (POD) 1, 2, 3, 5, and patients were followed for postoperative complications. Diagnostic accuracy of CRP and PCT values on each day was analyzed by the receiver operating characteristics (ROC) curve, with infectious complications as an outcome measure. ROC curves with the largest area under the curve for each inflammatory marker were compared in order to define the marker with higher diagnostic accuracy.

Results: Twenty nine patients (36.7%) developed infectious complications. CRP and PCT concentrations increased in the early postoperative period, with a significant difference between patients with and without complications at all measured postoperative times. ROC curve analysis showed that CRP concentrations on POD 3 and PCT concentrations on POD 2 had similar predictive values for the development of infectious complications (area under the curve, 0.746 and 0.750, respectively) with the best cut-off values of 99.0 mg/L for CRP and 1.34 μg/L for PCT. Diagnostic accuracy of CRP and PCT was highest on POD 5, however the cut-off values were not considered clinically useful.

Conclusion: Serial postoperative PCT measurements do not offer an advantage over CRP measurements for prediction of infectious complications following colorectal surgery.

Figure 1

C-reactive protein (CRP) concentrations the day before surgery and on postoperative days (POD) 1-5 in patients with and without complications after colorectal surgery. The box represents 25th-75th percentiles and line within the box is the median value. P = 0.026 on POD 1, P = 0.002 on POD 2, P < 0.001 on PODs 3 and 5 (Mann-Whitney test). Asterisk indicates the group without complications n = 50; group with complications n = 29. Dagger indicates the group without complications n = 42; group with complications n = 27.

Figure 2

Perioperative procalcitonin (PCT) concentrations in patients with and without complications after colorectal surgery. The box represents 25th-75th percentiles and line within the box is the median value. P = 0.003 on postoperative day (POD) 1, P ≤ 0.001 on PODs 2-5 (Mann-Whitney test). Asterisk indicates the group without complications n = 49; group with complications n = 29. Dagger indicates the group without complications n = 37; group with complications n = 21.

Figure 3

Diagnostic accuracy of early postoperative (postoperative day [POD] 1-3) C-reactive protein (CRP) and procalcitonin (PCT) concentrations with regard to infectious complications expressed by the receiver operating characteristic (ROC) curves. Comparison of ROC curves with the largest area under the curve for each biomarker on PODs 1-3 shows similar diagnostic accuracy of CRP on POD 3 and PCT on POD 2 with the area under the curve of 0.746 and 0.750, respectively.