Evaluation Of IL-8 As A Diagnostic Marker In The Diagnosis Of Bacterial Pneumonia

Background Bacterial pneumonia remains a leading cause of morbidity and mortality worldwide, particularly in developing countries. Early and accurate diagnosis is essential for improving patient outcomes and reducing inappropriate antibiotic use. Interleukin-8 (IL-8), a pro-inflammatory chemokine, has been implicated in the host immune response to bacterial infections and may serve as a diagnostic biomarker. Method This case–control study included 82 patients (aged 18–65 years) with clinically and radiologically confirmed bacterial pneumonia admitted to Al-Saahb Hospital, Iraq, between April 2024 and January 2025. A total of 68 healthy individuals without respiratory disease served as controls. Patients with recent antimicrobial therapy, chronic respiratory illness, autoimmune disorders, pregnancy, or lactation were excluded. Serum IL-8 levels were measured using ELISA according to standardized protocols. Results Mean serum IL-8 levels were significantly higher in pneumonia patients (92.4 ± 20.6 pg/ml) compared to controls (35.7 ± 11.8 pg/ml) (p < 0.001). IL-8 levels also varied according to bacterial etiology, with the highest concentrations observed in patients infected with Klebsiella pneumoniae and Pseudomonas aeruginosa. Receiver operating characteristic (ROC) curve analysis demonstrated strong diagnostic accuracy of IL-8, with an area under the curve (AUC) of 0.902. At a cut-off value of 60.0 pg/ml, IL-8 achieved a sensitivity of 87.8% and specificity of 81.5% in distinguishing pneumonia patients from controls (p < 0.001). Conclusion Serum IL-8 is markedly elevated in bacterial pneumonia and shows strong potential as a diagnostic biomarker. Its high sensitivity and specificity suggest that IL-8 measurement could complement conventional diagnostic methods, supporting early detection and improved management of pneumonia in clinical setting.