Sample taking during orthopedic surgery: sensitivity and specificity using the BACTEC blood culture system.

The use of blood culture systems for sterile body fluids other than blood has proven to be superior to routine culture methods. This study was conducted in order to assess the performance of the BACTEC blood culture system compared to swab/tissue sample collection for the detection of infection from intraoperative samples taken during surgical procedures. Sensitivity was determined by taking samples (BACTEC and swab/tissue samples) from patients with clinically evident infection (Infection group). Specificity was tested by taking the same sample sets from patients who had aseptic operations with no history of infection (Control group). The sensitivity was found to be much higher for the BACTEC group (50 isolates from 56 samples, sensitivity: 89%) compared to the swab/tissue samples (29 isolates out of 56 samples, sensitivity: 52%). The specificity was lower in the BACTEC group (32 isolates out of 44 samples, specificity: 27%) compared to the swab/tissue samples (1 isolate out of 44 samples, specificity: 98%). We conclude that BACTEC is useful for intraoperative sample collection in cases of low-grade infection. However, it is less specific and there is always the possibility for contamination. Therefore, it is advisable to use this technique in combination with regular tissue samples.