Is a Drain Tip Culture Required After Spinal Surgery?

STUDY DESIGN: The efficacy of use of a drain tip culture for early detection of surgical-site infection (SSI) was investigated in 329 patients after spinal surgery.

OBJECTIVE: To examine the efficacy of a wound drain tip culture for detection of SSI in spinal surgery.

SUMMARY OF BACKGROUND DATA: A complication of SSI after spinal surgery has high associated morbidity and mortality, and is often difficult to treat.

MATERIALS AND METHODS: The subjects were patients who underwent spinal surgery at our institution between January 2010 and March 2013. All subjects were treated with antimicrobial prophylaxis based on evidence-based guidelines and were followed for at least 6 months after surgery. Data from culture studies using the distal tip of the wound drain were used for analysis.

RESULTS: Drain tip cultures were positive in 34 cases and there were 19 SSIs. Ten of the 34-tip culture-positive wounds developed SSI. Drain tip cultures had a sensitivity of 52%, specificity of 92%, positive predictive value (PPV) of 29%, and negative predictive value of 97% for predicting a wound infection. The association between a positive suction tip culture and wound infection was significant (P<0.05). The PPV for SSI was 60% in cases in which methicillin-resistant bacteria were detected in a drain tip, and the SSI rate in these cases differed significantly compared with those with non-methicillin-resistant bacteria (P=0.01).

CONCLUSIONS: A drain tip culture is useful for early detection of SSI caused by methicillin-resistant bacteria.