Background: Atherosclerosis is known to be the most common underlying pathology of coronary artery disease (CAD). Leukocyte recruitment and proinflammatory cytokines were found to participate essentially in the process of atherogenesis. Systemic immune inflammatory index (SII) is derived by calculating both platelet counts and neutrophil/lymphocyte ratio (NLR) [ SII = platelets count *NLR]. SII is suggested to have prognostic value regarding mortality in patients with CAD, myocardial infarction (MI) and acute coronary syndromes (ACS).

Aim of the Work: to investigate the relation between the systemic inflammatory and immune state of the patient using SII and the extent of atherosclerosis of coronaries assessed by SYNTAX score in patients undergoing elective coronary angiography.

Patients and Methods: This cross-sectional study was conducted on 113 patients undergoing elective coronary angiography divided into three groups according to SII; Lower SII group (n=64), intermediate SII group (n=30), and High SII group (n=19).

Results: Our results showed statistically significant difference among the three groups regarding SYNTAX score being higher in intermediate SII group and high SII group compared to lower SII group with moderate positive correlation between SYNTAX score and SII. Moreover, SII was the most independent predictors for both low and high SYNTAX score.

Conclusion: SII is correlated with extent of CAD assessed by SYNTAX score among patients with chronic coronary syndrome (CCS) undergoing elective coronary angiography.