Background <p>Fracture related infections (FRI) are more commonly associated with open fractures. Currently available diagnostic criteria for FRI can diagnose them once infection is clinically apparent. Novel biomarkers procalcitonin and interleukin-6 have established a role in periprosthetic joint infections. We conducted this study to determine their role in predicting FRI in patients with open fractures undergoing staged, early definitive fixation conversion.</p> Methods <p>this was prospective, cohort study included patients undergoing definitive fixation of long bones within 2 weeks of primary external fixation in open fractures. Serum IL-6 and PCT levels were evaluated on day 0, day 3, day 7 of primary external fixator and 1&#xa0;day prior to definitive internal fixation. Sensitivity, specificity, PPV, NPV, LR+, LR-, Diagnostic accuracy and AUC in ROC curve were determined for both biomarkers individually as well as in combination.</p> Results <p>total 86 patients underwent primary external fixator application. 10 patients developed infection before definitive fixation. 28 patients were excluded after the first surgery but prior to definitive fixation due to wound dehiscence, pin-tract infection, or unfit for second surgery. A total of 48 patients underwent definitive fixation, out of them 5 developed infections in follow-up. Hence a total of 15 patients were in infection cohort. PCT had better Sensitivity than IL-6 alone or with IL-6 and PCT combined whereas IL-6 and PCT combined had better specificity. Both biomarkers had poor PPV, but good NPV Both biomarkers had good diagnostic accuracy when used in combination (Table&#xa0;2). Combination of these two tests had better AUC then individually. (Table&#xa0;2, Figures 2,3,4)</p> Conclusion <p>Procalcitonin and IL-6 are good predictors of infection when used before definitive fixation while early (within 2 weeks) conversion from external fixation. However, these results require studies with larger sample size and higher number of cases in both groups.</p>