Systemic immune-inflammation index, and neutrophilto-lymphocyte and platelet-to-lymphocyte ratios can predict clinical outcomes in patients with acute coronary syndrome.

Objective: Inflammatory mechanisms play an important role in the pathogenesis of atherosclerosis and myocardial infarction. The clinical and prognostic importance of inflammatory parameters, such as neutrophil-lymphocyte (NLR) and platelet-lymphocyte ratios (PLR) in complete blood counts in acute myocardial infarction and other cardiovascular diseases has been demonstrated. However, systemic immune-inflammation index (SII) calculated from neutrophils, lymphocytes and platelets in the complete blood cell count has not been studied sufficiently and is thought to provide a better prediction. This study investigated whether haematological parameters such as SII, NLR and PLR were associated with clinical outcomes in acute coronary syndrome (ACS) patients.

Methods: We included 1 103 patients who underwent coronary angiography for ACS between January 2017 and December 2021. The association between major adverse cardiac events (MACE) that developed in hospital and at 50 months of follow up and SII, NLR and PLR was compared. Long-term MACE were defined as mortality, re-infarction and target-vessel revascularisation. SII was calculated using the formula: NLR × total platelet count in the peripheral blood (per mm).

Results: Of the 1 103 patients, 403 were diagnosed with ST-elevation myocardial infarction and 700 with non-STelevation myocardial infarction. The patients were divided into a MACE and a non-MACE group. In hospital and during the 50-month follow up, 195 MACE were observed. SII, PLR and NLR were found to be statistically significantly higher in the MACE group ( < 0.001). SII, C-reactive protein level, age and white blood cell count were independent predictors of MACE in ACS patients.

Conclusions: SII was found to be a strong independent predictor of poor outcomes in ACS patients. This predictive power was greater than that of PLR and NLR.