Diagnostic and prognostic values of selected biomarkers as a vital indicator in critically ill patients

Objectives: The accurate diagnosis and prognostic assessment of Critically ill patients with pneumonia remain challenging, necessitating the evaluation of multiple biomarkers to enhance clinical decision-making. This study aimed to investigate the diagnostic and prognostic value of interleukin-6 (IL-6), procalcitonin (PCT), C-reactive protein (CRP), selenium, lactate, soluble urokinase plasminogen activator receptor (suPAR), and peptidyl arginine deiminase 2 (PAD2), and to determine their associations with disease severity and mortality. Methods: A prospective observational cohort study was conducted on 130 critically ill pneumonia patients and 45 non-critically ill outpatient controls. Biomarker levels were assessed using ELISA, PCR, and standard biochemical assays, and correlated with severity indices and clinical outcomes. Results: Lactate, PCT, CRP, IL-6, and PAD2 levels were significantly elevated in patients versus controls (p < 0.001), with higher levels observed in non-survivors (p < 0.001) except for PAD2 levels were not significantly associated with survival status (p = 0.346). Although suPAR and selenium differed between patients and controls, they did not distinguish survivors from non-survivors. suPAR correlated positively with PCT, while PAD2 showed significant associations with inflammatory markers and severity scores. No biomarker demonstrated superior prognostic accuracy. Conclusion: Lactate, PCT, CRP, IL-6, and PAD2 exhibit diagnostic relevance in pneumonia. Several biomarkers, including IL-6 gene expression, IL-6, CRP, PCT, and lactate, demonstrated excellent prognostic discrimination (AUC >0.95). However, comparative ROC analysis revealed no statistically significant superiority of any single biomarker over the others, suggesting that a multimarker approach may provide greater clinical value than reliance on an individual marker.