Interleukin-6 and high-sensitivity C-reactive protein in chronic coronary syndromes: pathophysiological rationale and clinical interpretation in stable angina

Chronic coronary syndromes (CCS) are driven by atherosclerosis in which inflammation contributes to plaque progression and adverse events. Interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hs-CRP) are linked, non-equivalent bio-markers along the IL-6 → hepatic acute-phase response → CRP axis. This narrative review summarizes the biological rationale and clinical evidence on IL-6 and hs-CRP as diagnostic and prognostic biomarkers in CCS, emphasizing stable cohorts assessed with invasive coronary angiography or coronary CT angiography. Available data suggest IL-6 is more consistently associated with the presence and burden of coronary atherosclerosis, whereas hs-CRP is more robustly validated for prognostic risk stratification but shows heterogeneous associations with anatomic stenosis severity. Both markers are nonspecific and influenced by metabolic comorbidity and background therapy; therefore, they should be interpreted as adjuncts rather than standalone diagnostic tests. Standardized studies with uniform angiographic endpoints are needed to define incremental diagnostic value and clinically relevant thresholds.