Association of procalcitonin levels with multidrug-resistant bloodstream infections: a prospective cohort study

BACKGROUND: Procalcitonin (PCT) is widely used for early detection of bloodstream infections. However, limited data correlate PCT levels with infection aetiology, especially in identifying multidrug-resistant (MDR) pathogens. METHODS: This prospective study included patients with bloodstream infections (BSIs) from January 2022 to April 2024. Patients with positive blood cultures and simultaneous PCT testing were enrolled. The primary objective was to evaluate the association between PCT levels and MDR bacteremia. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of PCT. RESULTS: A total of 317 patients with positive blood cultures met the inclusion criteria. Of these, 186 (58.7%) had MDR bacteremia, while 131 (41.3%) were due to non-MDR pathogens. Gram-negative (GN) bacteremia accounted for 238 cases, and Gram-positive (GP) bacteremia for 79 cases. Median PCT values were significantly higher in MDR bacteremia (9.6, IQR: 3.4-17.1 ng/mL) compared to non-MDR (1.5, IQR: 0.5-4 ng/mL, p < 0.001). ROC analysis showed an area under the curve (AUC) of 0.71 for PCT and 0.47 for CRP in predicting MDR bacteremia. For GN bacteremia prediction, the AUC was 0.61 for PCT and 0.39 for CRP. PCT values were highest in urinary tract infections, followed by pneumonia and soft tissue infections (11.75, 5.65, and 5.1 ng/mL, respectively). CONCLUSIONS: PCT demonstrated moderate ability to discriminate MDR bacteremia. However, these results do not support its use as a standalone marker and must be interpreted with clinical and microbiological findings.