The novel role of serum IL-6 and IL22 Levels as diagnostic biomarkers for the infection caused by Mycobacterium tuberculosis

Abstract

Interleukin-6 (IL-6) and interleukin-22 (IL-22) are major immunoregulatory cytokines that mediate inflammatory activation and affect antimicrobial defence mechanisms. This study aims to investigate the role of serum IL-6 and IL-22 levels as diagnostic biomarkers in patients with Mycobacterium tuberculosis. This is a hospital-based case–control study that consisted of 48 patients with Mycobacterium tuberculosis infection and 62 apparently healthy control subjects recruited from Al-Hussein Teaching Hospital at Karbala City, Iraq for the period between April (2025) to March (2026). Patients were grouped as active tuberculosis (n = 39) and latent tuberculosis infection (n = 9). Severe tuberculosis-related disease was also associated with significantly increased circulating levels of IL-6 and IL-22. The cytokine levels were higher in patients with active TB compared to individuals that showed latent TB infection. Both biomarkers were acceptable for their diagnostic performance as assessed by ROC curve analysis. Interleukin-6 had an area under the curve of 0.741 with sensitivity and specificity at 76.4% and 72.5%, respectively, at a cut-off value of 32.8 pg/mL. IL-22 was shown to have a slightly better diagnostic value, with an AUC of 0.768 (sensitivity 77.0%, specificity 74.2% cut-off, 46.7 pg/mL). IL-6 and IL-22 are upregulated, especially in active TB where inflammatory and immune responses predominate. Both , especially IL-22 , may also be helpful as supplement biomarkers for the differentiation of tuberculosis patients from healthy subjects, and active disease from latent infection.