Comparative Evaluation of Procalcitonin and Interleukin-6 as Diagnostic and Prognostic Biomarkers for Sepsis

Introduction: Diagnosis of sepsis is based on host's systemic inflammatory response to infection including life-threatening organ dysfunction. Various biomarkers are available for diagnosis and prognostication of patients with sepsis, Procalcitonin (PCT) and interleukin-6 (IL-6) being most reliable. Aim: To compare PCT and IL-6 as diagnostic and prognostic biomarkers of sepsis in patients admitted with Systemic Inflammatory Response Syndrome (SIRS). Materials and Methods: After taking Ethical Committee Approval, a total of 51 patients aged 15-65 years admitted in ICU with SIRS were identified. Patients with baseline Sequential Organ Failure Assessment (SOFA) score of 0 and 1 were categorised into non-infectious group and SOFA of greater than 2 into infectious group. Procalcitonin and IL-6 were measured on day 1 and 3 using enzyme-linked immunosorbent assay. Collected data were analysed using SPSS software version 22.0. Parametric data were compared using Student's t-test. Other tests used were Mann-Whitney U test, Pearson's chisquare test, Fisher's-exact test, Friedman's test, ANOVA. Results: PCT (day 1 and 3) was significantly higher in the infectious group than non-infectious group (p<0.001) and day 1 PCT was found to be better in diagnosing sepsis with Area Under the Curve (AUC) of 0.90 (95% CI, 0.789-1.000) (p=0.001). Unlike day 1 PCT, day 3 PCT was statistically significant in predicting mortality with AUC of 0.982 (95% CI, 0.956-1.000) (p<0.005). IL-6 was found to be better in predicting mortality with day 1 AUC of 0.987 (95% CI, 0.966-1.000) (p<0.005) and day 3 AUC of 0.981 (95%Cl, 0.953-1.000) (p<0.005). Multivariate analysis of mortality prediction showed day 1 IL-6 to have a better mortality prediction value (p=0.047). Conclusion: PCT on day 1 was found to be better in identifying sepsis and day 1 IL-6 and day 3 PCT in predicting mortality.