Interleukin-6 and high-sensitivity C-reactive protein for the prediction of outcomes in non-ST-segment elevation acute coronary syndromes

Abstract

Introduction and objectives: High baseline levels of interleukin-6 and C-reactive protein confer an increased risk of mortality in non-ST-segment elevation acute coronary syndrome. The aim of the study was to determine whether serial measurements of interleukin-6 and high-sensitivity C-reactive protein provide additional information to baseline measurements for risk stratification of non-ST-segment elevation acute coronary syndrome.

Methods: Two hundred and sixteen consecutive patients with non-ST-segment elevation acute coronary syndrome were prospectively included. Blood samples were obtained within 24 h of hospital admission and at 30 days of follow-up. The endpoint was a composite of all-cause death, nonfatal myocardial infarction, or acute decompensated heart failure.

Results: Both interleukin-6 and high-sensitivity C-reactive protein levels decreased from day 1 to day 30, regardless of adverse events (both P<.001). Interleukin-6 levels at 2 time points (interleukin-6 day 1, per pg/mL; hazard ratio=1.006, 95% confidence interval, 1.002-1.010; P=.002 and interleukin-6 day 30, per pg/mL, hazard ratio=1.047, 95% confidence interval, 1.021-1.075, P<.001) were independent predictors of adverse events, whereas high-sensitivity C-reactive protein day 1 and high-sensitivity C-reactive protein day 30 levels were not. Patients with interleukin-6 day 1≤8.24 pg/mL and interleukin-6 day 30≤4.45 pg/mL had the lowest event rates (4.7%), whereas those with both above the median values had the highest event rates (35%). After addition of interleukin-6 day 30 to the multivariate model, C-index increased from 0.71 (95% confidence interval, 0.63-0.78) to 0.80 (95% confidence interval, 0.72-0.86), P=.042, and net reclassification improvement was 0.39 (95% confidence interval, 0.14-0.64; P=.002).

Conclusions: In this population, both interleukin-6 and high-sensitivity C-reactive protein concentrations decreased after the acute phase. Serial samples of interleukin-6 concentrations improved the prognostic risk stratification of these patients.