Serum procalcitonin in the diagnosis of pneumonia in the neurosurgical intensive care unit

Procalcitonin (PCT) is a biomarker for bacterial infections, with controversial utility in diagnosing hospital-acquired pneumonia (HAP) in neurosurgical intensive care unit (NICU) patients. Establishing an optimal PCT cutoff value could enhance diagnostic accuracy. This retrospective single-center study included NICU patients hospitalized between January 1, 2021, and December 31, 2022, who underwent routine serum PCT measurement. HAP was diagnosed based on clinical, biochemical, microbiological, and radiological data. The optimal PCT cutoff value was identified using the Youden Index. Associations between PCT levels, radiological findings, sputum cultures, and confirmed HAP were analyzed using chi-square tests. A multivariate logistic regression was performed to identify independent predictors of elevated PCT. Among 2363 patients, 193 met inclusion criteria, and 148 were diagnosed with HAP. The optimal PCT cutoff value was 0.095 ng/mL, yielding a sensitivity of 89.2% and specificity of 93.3% (p < 0.001). This cutoff resulted in a positive likelihood ratio of 13.3 and a negative likelihood ratio of 0.116. Radiological signs of pneumonia and positive sputum cultures were observed in 48.4% and 78.4% of HAP cases, respectively, but neither showed a significant association with HAP (p = 0.135 and p = 0.056). Leukocytosis was significantly associated with HAP but had low specificity, while CRP showed a non-significant trend. In multivariate analysis, only confirmed HAP independently predicted PCT elevation. PCT, with a cutoff value of 0.095 ng/mL, shows high diagnostic accuracy for HAP in NICU patients and could enhance early identification and treatment. Our findings suggest that elevated PCT is primarily driven by HAP rather than non-infectious inflammatory triggers such as trauma or recent surgery. Further prospective studies are warranted to validate these findings.