The Use of Procalcitonin in the Determination of Severity of Sepsis, Patient Outcomes and Infection Characteristics

Objective: The primary objective of this study was to determine the correlation between procalcitonin values and illness severity by evaluating the degree of end organ dysfunction using the Sequential Organ Failure Assessment score, length of stay and the severity of sepsis (sepsis alone vs. septic shock), The hypothesis that procalcitonin values would be higher in sicker patients was formulated before data collection began. Secondary outcomes studied in relation to procalcitonin levels included infection characteristics such as the site of infection, microbial agent and dialysis dependent CKD.

Design: Unblinded retrospective cohort study. September 2014-December 2016.

Setting: 364 patients with a diagnosis of sepsis or severe sepsis who were admitted to the general medical ward and ICU at Methodist Medical Center and Proctor Hospital in Peoria, Illinois, USA.

Results: This study demonstrates the following: Weak positive correlation between procalcitonin and SOFA score. Negligible correlation with length of stay. Higher values in patients who died than in patients who survived to discharge (p = 0.058). Sensitivity and specificity of procalcitonin for septic shock was 63 and 65% respectively. Sites typically infected by gram negative bacteria have higher procalcitonin values than sites infected by gram positive bacteria (p = 0.03). Higher procalcitonin in bacteremia than non-bacteremic infections (p = 0.004). Higher procalcitonin in dialysis-dependent CKD patients (p = 0.020).

Conclusions: Procalcitonin has a higher specificity for bacterial infections than other acute phase reactants. Although initial procalcitonin value may be helpful in the determination of illness severity, it is not always a reliable prognostic indicator and carries little significance as a standalone value. Procalcitonin values may be influenced by preexisting comorbid conditions such as chronic kidney disease, which are associated with higher procalcitonin values at baseline. Procalcitonin can provide invaluable information when viewed as one piece of a clinical puzzle, and is most powerful when the interpreting physician is aware of how values are influenced by the different clinical scenarios presented in this article.