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

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.Colorectal surgery leads to high rates of postoperative complications, varying between 28% and 38% (1-3). Early diagnosis and prompt treatment of complications is crucial for a favorable outcome. However, surgical trauma induces systemic inflammatory response syndrome (SIRS), which can hinder the diagnosis of postoperative infections (4). Therefore, it would be useful to find a biochemical marker that could accurately differentiate between infectious and non-infectious SIRS.C-reactive protein (CRP), the first of the acute phase proteins to be described, was discovered in 1930 and named for its capacity to precipitate a non-protein somatic fraction (Fraction C) of Streptococcus pneumoniae. It is a sensitive systemic marker of inflammation and tissue damage, but is not specific for infection (5,6). Surgical trauma induces a significant increase in CRP levels, which can reduce its predictive value for the diagnosis of infection in the early postoperative period (7-9). Despite this, an interest in CRP as an infection monitoring tool in the perioperative setting has increased since it was reported that in values higher than 140 mg/L on the postopertaive day (POD) 3-4 it well predicted infectious complications after colorectal surgery (10). Since then, several studies have found it to be a useful predictor of septic complications following colorectal and esophagogastric resections (11-15).Procalcitonin (PCT), the prohormone of calcitonin, was first described as a biochemical marker of infection in 1993 (16). Bacterial endotoxins are potent stimuli for PCT synthesis, which exhibits faster kinetics than CRP. PCT is released into the circulation 3-4 hours after an injection of endotoxin, reaching peak levels after 8-24 hours, while CRP peaks at 36-50 hours after stimulus (5,17). This would make PCT more suitable as an infection monitoring tool in the perioperative setting (18,19). A meta analysis of 33 studies, which included adults in intensive care units or after surgery and trauma, showed that PCT was a good diagnostic marker of sepsis, with greater diagnostic accuracy than CRP (20). Recent studies in surgical patients have also shown that after orthopedic, cardiac, and thoracic surgery PCT was better for detecting postoperative infections than CRP (21-23).To the best of our knowledge, no studies have compared the diagnostic accuracy of CRP and PCT for early detection of postoperative complications in patients undergoing colorectal surgery. The aim of this study was to assess the predictive value of serial postoperative determinations of CRP, PCT, and white blood cell (WBC) count for infectious complications after elective colorectal surgery and to compare the diagnostic accuracy of CRP and PCT.