Evaluating the systemic immune-inflammation index for in-hospital and long-term mortality in elderly non-ST-elevation myocardial infarction patients

Abstract

This investigation aimed to evaluate the predictive value of the systemic immune-inflammation index (SII) for in-hospital and long-term mortality in elderly patients with non-ST-elevation myocardial infarction (NSTEMI). This retrospective investigation included 314 consecutive elderly NSTEMI patients in a tertiary center. SII is computed as (neutrophils × platelets)/lymphocytes. Based on the increased SII values, we classified the research sample into three tertile groups as T1, T2, and T3. The in-hospital and long-term mortality were defined as the primary outcomes. Patients in the T3 group had lower chances of survival in the in-hospital and long-term periods compared with those in the T2 and T1 groups. According to the multivariable Cox regression models, SII independently related with in-hospital (hazard ratio (HR): 1.001, 95% CI: 1.000-1.1003, p = 0.038) and long-term mortality (HR: 1.004, 95% CI: 1.002-1.006, p < 0.001). To predict long-term mortality, the optimal SII value was > 2174 with 80% sensitivity and 85.4% specificity. SII had a slightly lower but statistically non-inferior discriminative ability for long-term mortality compared with the Charlson comorbidity index (CCI) in the receiver operating characteristic curve comparison (AUC: 86.2 vs. AUC: 890, p > 0.05). Additionally, combining SII with traditional risk factors and the CCI revealed a significant improvement in C-statistics. This investigation may be the first to demonstrate that SII is independently linked with in-hospital and long-term mortality in elderly NSTEMI patients.