Serum C-reactive protein levels correlate with clinical response in patients treated with antibiotics for wound infections after spinal surgery.

BACKGROUND CONTEXT: C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been used to diagnose postoperative infections after spinal surgery. However, it has not been demonstrated if resolution of the signs and symptoms of postoperative spinal wound infections in patients who are being treated with intravenous antibiotics correlates with these markers.

PURPOSE: The objective of this study was to determine if improvement of the signs and symptoms of postoperative wound infection after spinal surgery correlates with a decrease in serum CRP and ESR while intravenous antibiotics are administered.

STUDY DESIGN: Retrospective review.

PATIENT SAMPLE: The study consisted of 21 patients (mean age 63.8 years; 13 female, 8 male) with postoperative wound infections after spinal surgery. They were studied for a minimum of 20 weeks.

OUTCOME MEASURES: CRP and ESR were measured at the time of diagnosis and at serial time-points.

METHODS: All patients received intravenous antibiotic therapy for 6-8 weeks. Patients were monitored for clinical signs and symptoms of infection such as fever, drainage, erythema, or a need for continued wound packing at 4, 7, and 20 weeks after being diagnosed with a wound infection.

RESULTS: The average CRP for all 21 patients at time of diagnosis was 11.7+/-9.0 mg/dL (range 1.2 to 37.8 mg/dL). At the 4-week time-point, 16 patients ("early responders") showed clinical improvement with no fevers, no wound drainage, no erythema, and no need for wound packing. The average CRP of this group at the 4-week time-point decreased to 0.3+/-0.5 mg/dL. In contrast, at the 4-week time-point five patients ("late responders") still had signs and symptoms of infection (2 with continuing drainage requiring wound packing; 1 with vertebral osteomyelitis requiring irrigation and debridement; 2 with erythema without fevers). The average CRP for this group was still elevated at the 4-week time-point at 7.3+/-3.5 mg/dL. The CRP value difference was statistically significant between the two groups (p<.05). As treatment continued, at the 20-week time-point the average CRP of the late responders gradually decreased to 0.8+/-0.8 mg/dL, which was not statistically different from that of the early responders (average CRP=0.6+/-1.1 mg/dL). All 21 patients had resolution of infection at the 20-week time-point. The ESR did not correlate well with clinical improvement. At time of diagnosis, the ESR of both early responders (average=57.6+/-27.6 mm/hr) and late responders (average=64.0+/-21.9 mm/hr) was elevated. It remained elevated for both groups from the beginning of the study to the end at all time-points. The final ESR at the 20-week time-point was not different between the early responders and late responders (average=27.6+/-22.3 mm/hr vs. 31.0+/-2.6 mm/hr, respectively; p>.05).

CONCLUSIONS: Our data suggest that CRP may be of value in following the treatment response to antibiotics in wound infections after spinal surgery. The ESR can remain elevated in the presence of a normal CRP despite a resolution of clinical signs and symptoms of postoperative wound infection.