Procalcitonin ratio and on-demand relaparotomy for septic peritonitis: validation of the focus index (FI)

Purpose Secondary peritonitis remains challenging to manage and some recent evidence suggests that on-demand relaparotomy is more appropriate than planned relaparotomy. This study was designed to validate the predictive power of postoperative procalcitonin (PCT) changes in relation to elimination of the septic abdominal focus. Methods In this prospective trial, postoperative PCT serum levels were monitored in 234 surgical patients with secondary peritonitis. The PCT ratio on postoperative days (PODs) 1 and 2 (focus index; FI) was calculated and correlated with the success of the operation. Results A cutoff value of 1.1 was calculated for the FI. Values below 1.1 indicated insufficient elimination of the focus and values above 1.1 correlated with effective treatment. The optimal time for first PCT sampling was found to be 12–24 h after the index operation. After the respective data cleanup, successful elimination of the intraabdominal focus could be confirmed, with a sensitivity of 93 % and a specificity of 71 %. Conclusions The FI is a single parameter-based reliable predictor of successful surgical eradication and strengthens the on-demand relaparotomy concept as the method of choice to treat secondary peritonitis.