Usefulness of White Blood Cell Differential for Early Diagnosis of Surgical Wound Infection Following Spinal Instrumentation Surgery

Study Design. The white blood cell (WBC) count and WBC differential were measured prospectively in patients after spinal instrumentation surgery with or without surgical wound infection. Objectives. To investigate the usefulness of WBC differential for early diagnosis of surgical wound infection after spinal instrumentation surgery. Summary of Background Data. Renewed elevation of C-reactive protein (CRP) or WBC, gallium scan, and CRP/transthyretin mass concentration ratio were reported for early diagnosis of surgical wound infection. Methods. A total of 39 patients were enrolled in this study: 13 patients who developed wound infection within 2 weeks after spinal instrumentation surgery (infection group) and 26 patients who were comparable with those patients included in the infection group with regard to age, sex, and surgical techniques used (control group). The WBC count and WBC differential were determined before and after surgery. Results. In both groups, WBC and percentage and number of neutrophils showed nearly same change until postoperative 4 days (day 4). However, in the infection group, these parameters had increased after day 4. In both groups, the percentage and number of lymphocytes decreased to 10% or less and 1,000/&mgr;L or less on day 1, respectively. These lymphocyte parameters began to gradually normalize on day 4 and returned to the preoperative level 3 weeks after surgery in the control group. On the other hand, these parameters remained 10% or less and 1,000/&mgr;L or less until day 11 in the infection group. In patients with infection, the percentage and number of lymphocytes significantly decreased as early as on day 4. Conclusion. Lymphopenia represents immunodepression status, thus indicating the increased susceptibility to infection, which may lead to the development of postoperative infection. If lymphopenia is diagnosed as early as possible, surgical wound infection can be treated promptly without removing the instruments.