Procalcitonin as a rapid diagnostic biomarker to differentiate between culture-negative bacterial sepsis and systemic inflammatory response syndrome: a prospective, observational, cohort study

Abstract

Purpose: Differentiation between culture-negative sepsis and noninfectious systemic inflammatory response syndrome (SIRS) remains a diagnostic challenge for clinicians, both conditions having similar clinical presentations. Therefore, a swift accurate diagnostic tool, which helps differentiate these 2 conditions would immensely aid appropriate therapeutic continuum. This prospective study was conducted to evaluate the potential diagnostic role of biomarkers, procalcitonin (PCT) and interleukin 6 (IL-6), in culture-negative sepsis patients.

Methods: Enrolled patients (208) included 46 noninfectious SIRS, 90 culture-negative sepsis, and 72 culture-positive sepsis. Culture, PCT, and IL-6 estimations were performed on day 1 of intensive care unit admission.

Results: Procalcitonin and IL-6 levels were significantly higher (P < .001) in both culture-negative and culture-positive groups as compared with SIRS group. Procalcitonin was a better predictor of sepsis in both culture-negative (area under curves 0.892 vs 0.636) and culture-positive (area under curves 0.959 vs 0.784) groups as compared with IL-6. In culture-negative group, the best cutoff point for PCT was at 1.43 ng/mL (92% sensitivity; 83% negative predictive value), best cutoff point for IL-6 was at 219.85 pg/mL (47% sensitivity and 42% negative predictive value).

Conclusions: Procalcitonin can accurately differentiate culture-negative sepsis from noninfectious SIRS and thereby contribute to early diagnosis and effective management of these conditions.

Keywords: Culture negative; Interleukin 6 (IL-6); Negative predictive value (NPV); Procalcitonin (PCT); Sepsis; Systemic inflammatory response syndrome (SIRS).