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Clinical utility of procalcitonin testing in critically Ill COVID-19 patients: a two-center retrospective cohort study

Year: 2026

Type: article

Abstract: Procalcitonin (PCT) is particularly sensitive to bacterial infections due to its response to specific bacterial cytokines. Even though viruses generally do not induce these cytokines, PCT levels are frequently ordered for viral infections in practice. However, among patients with COVID-19, it remains unclear whether baseline PCT measurements or change in PCT levels overtime are strongly associated with bacterial co-infection and clinical outcomes. Therefore, this study evaluated the association between baseline and dynamic procalcitonin (PCT) levels and microbiological and clinical outcomes in critically ill patients with COVID-19. A two-center retrospective cohort study included adult critically ill patients with COVID-19 who were hospitalized in intensive care units (ICUs) between March 2020 and December 2021. Eligible patients were divided into two sub-cohorts: those with PCT values < 0.25 ng/mL and those with values ≥ 0.25 ng/mL. The primary outcome was the rate of positive bacterial and fungal cultures within five days. Propensity score (PS) matching with a 1:1 ratio was used. Regression analyses were performed as appropriate. PCT monitoring was performed as part of routine clinical care rather than under a standardized prospective protocol, and dynamic PCT analyses were therefore based on clinically obtained follow-up values within the predefined window. A total of 553 patients were included. After PS matching, 184 patients were included in each group. Patients who had a baseline PCT ≥ 0.25 had higher odds for the positivity of bacterial and fungal cultures; however, this was not statistically significant (OR 1.36 (CI 0.75, 2.45); p-value = 0.29 and OR 2.07 (CI 0.60, 7.11); p-value = 0.24, respectively). In the subgroup analysis based on the change in PCT from baseline, 30-day mortality was significantly higher in the PCT increase group in both the crude and regression analyses (40.4% vs. 25%; p-value = 0.02 and OR 2.07 (CI 1.08, 3.92); p-value = 0.02, respectively). Our findings show that dynamic increases in procalcitonin correlate with higher mortality rates and poorer outcomes, while baseline PCT did not show a statistically significant association with early microbiological outcomes, limiting its utility as a stand-alone marker of bacterial or fungal co-infection. These findings support a cautious interpretation of PCT in critically ill COVID-19 patients, with greater emphasis placed on its dynamic trends rather than baseline values alone.

Source: Scientific Reports

DOI: 10.1038/s41598-026-71286-8