White Blood Cell Count and C-Reactive Protein Variations After Posterior Surgery With Intraoperative Radiotherapy for Spinal Metastasis.

STUDY DESIGN: Retrospective case series.

OBJECTIVE: To evaluate the feasibility of blood test parameters [white blood cell (WBC) count and C-reactive protein (CRP)] for predicting and diagnosing postoperative infection after posterior surgery with intraoperative radiotherapy (IORT) for spinal metastasis.

SUMMARY OF BACKGROUND DATA: Posterior surgery with IORT is effective for treating spinal metastasis, as we previously reported. However, the procedure requires that the patient be transferred from the operating room to the irradiation room. In addition, the patient's general status is often poor, and the risk of postoperative infection is high.

MATERIALS AND METHODS: A total of 279 patients who underwent IORT for the treatment of spinal metastasis between August 2004 and June 2013 were included in this study. The WBC count (/10 μL) and CRP level (mg/dL) were recorded in all patients preoperatively and on alternative days for up to 7 days after surgery. We assessed the development of surgical-site infection (SSI) for up to 1 month after surgery.

RESULTS: SSI occurred in 41 patients (14.7%). The preoperative WBC count and CRP level did not differ between the infected and noninfected patients. The WBC counts on postoperative day (POD) 1 and POD 7 and the CRP levels on POD 7 were significantly higher in the infected patients (8.8 vs. 10.0, P=0.04; 6.1 vs. 8.8, P=0.002; 3.89 vs. 9.50, P<0.001). A receiver-operating characteristic curve analysis of the WBC count and CRP level for detecting SSI showed cutoff values of 9.6 (WBC count, POD 1), 6.5 (WBC count, POD 7), and 5.0 (CRP level, POD 7).

CONCLUSIONS: A high WBC count and CRP level on POD 7 may be used to predict or detect SSI. In particular, a CRP level of 5.0 mg/dL on POD 7 strongly suggests the future development of SSI (sensitivity: 78%, specificity: 74%).