Use of C-reactive protein after spinal surgery: comparison with erythrocyte sedimentation rate as predictor of early postoperative infectious complications.

STUDY DESIGN:
This is a prospective observational study of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in a cohort of patients undergoing spinal surgery.

OBJECTIVE:
We sought to characterize the normal kinetics of ESR and CRP after spinal surgery and compare their usefulness as predictors of infectious complications in the early postoperative period.

SUMMARY OF BACKGROUND DATA:
ESR and CRP are nonspecific markers of inflammation used to evaluate postoperative infection. CRP is a quantitative test that exhibits predictable kinetics consisting of a postoperative rise and a peak followed by a decrease toward the normal value. Deviation from normal kinetics may be an indicator of infection.

METHODS:
ESR and CRP were collected before surgery and daily after surgery in consecutive patients. All infectious complications were recorded.

RESULTS:
One hundred forty-nine patients met inclusion criteria. Infectious complications occurred in 20 patients. A postoperative peak, which is necessary to apply the test, was observed in 78% of patients for CRP and 48% for ESR. Multiple linear regression analysis revealed preoperative CRP, number of levels, and lumbar region as significant predictors of greater CRP peak value (r = 0.435, P = 0.001). After the peak, CRP showed an exponential decrease with a half-life of 2.6 days (r = 0.701, P < 0.001). No trend could be determined for ESR. A second rise or failure to decrease as expected had a sensitivity, specificity, positive predictive value, and negative predictive value of 82%, 48%, 41%, and 86% for infectious complications, respectively. Of 8 cases of deep wound infection, 7 exhibited substantial deviations from expected CRP values.

CONCLUSION:
CRP is more applicable, predictable, and responsive in the early postoperative period compared with ESR. The postoperative kinetics of CRP derived in this study seems to be conserved regardless of operation, magnitude, or region. Knowledge of the kinetics allows assessment of the degree of difference between actual and expected values. Using a second rise or failure to decrease as expected for CRP is sensitive for infection. A negative test is reassuring that infection is unlikely.