Clinical Microbiology and Antimicrobial Chemotherapy. 2025; 27(1):11-17
To determine role of ferritin (FT), procalcitonin (PCT) and their ratio (FT/PCT) in the differential diagnosis of viral lung injury and bacterial community-acquired pneumonia (CAP).
A prospective multicenter study included adult patients with CAP hospitalized in multidisciplinary hospitals from July to November 2023. All patients had their PCT and FT levels determined in addition to the standard examination protocol. Etiological diagnostics included microbiological examination of a respiratory sample and blood (in severe cases), rapid tests for pneumococcal and legionella antigenuria, and molecular testing of respiratory samples to detect DNA/RNA of the most common respiratory viruses and difficult-to-culture or non-cultivate bacterial pathogens.
Of the 152 patients included, the etiology of CAP was established in 96 cases: viral in 28 (29%), bacterial in 52 (54%), bacterial-viral coinfections in 16 (17%). Among bacterial pathogens, Mycoplasmoides pneumoniae accounted for a significant share – 62%. Comparative analysis of patients with CAP of viral and bacterial etiology revealed a lower level of FT in viral (127.5 versus 242 μg/L, p = 0.013), no significant differences were obtained in assessing PCT and the FT/PC ratio. After excluding cases of M. pneumoniae infection, significant differences remained: FT – 127.5 vs. 338.5 μg/L (p = 0.002), as well as PCT 0.1 vs. 0.4 ng/mL (p = 0.01). The cutoff values of FT >146 μg/L (AUC = 0.76; OR = 8.0) and PCT >0.15 ng/mL (AUC = 0.70; OR = 5.4) had a prognostic value for the diagnosis of bacterial CAP, when excluding cases of M. pneumoniae infection. Doubling the level of FT and PCT was associated with an increase in the likelihood of bacterial CAP by 1.8 (95% CI: 1.3-2.9) and 1.23 (95% CI: 1.05-1.48) times, respectively.
The study of the FT/PCT ratio did not have sufficient diagnostic accuracy in differentiating viral lung damage from bacterial CAP in adult patients in our study population; statistically significant but not clinically significant values were obtained when assessing PCT, and the determination of FT demonstrated some value; however, larger studies with groups of patients comparable in severity are needed for reliable use of this biomarker in clinical practice.