Background: Procalcitonin (PCT) is a biomarker that can help identify bacterial infections but can be difficult to interpret in the presence of renal dysfunction, which can elevate PCT even in the absence of infection. Objective: To determine the optimal PCT threshold to identify infection in patients with renal dysfunction and pneumonia or sepsis. Methods: A retrospective analysis was performed for inpatients with creatinine clearance of ≤60 mL/min and PCT level from 2018 to 2019. A pharmacist blinded to study outcomes classified patients as infected or noninfected based on predetermined criteria. Receiver operating characteristic curve analysis was performed to establish the optimal PCT threshold overall, as well as in subgroups of patients with chronic kidney disease (CKD), acute kidney injury (AKI), and end-stage renal disease (ESRD). Institutional review board approval was obtained. Results: A total of 198 patients were included in the study (99 infected, 99 noninfected). The optimal threshold in the AKI, CKD, and ESRD subgroups was determined to be 1.5 ng/mL, 0.1 ng/mL, and 1.75 ng/mL, respectively. Conclusion: The results of this study show that PCT thresholds were specific to type of renal dysfunction. These results differ from the traditionally accepted PCT threshold of 0.5 ng/mL for sepsis and 0.25 mg/mL for pneumonia. Future studies should confirm the appropriate PCT threshold in ESRD and CKD patient populations.
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