Interleukin-6 and C-reactive protein prognostic value following acute coronary syndrome

BACKGROUND AND AIMS: After acute coronary syndrome (ACS), high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) levels have been associated with risk of major adverse cardiovascular events (MACE). Whether the prognostic information provided by hsCRP and IL-6 is independent and complementary after ACS is unclear. METHODS: The ODYSSEY OUTCOMES trial compared alirocumab with placebo in post-ACS patients on optimized statin therapy. In post hoc analyses, the relation between log-transformed hsCRP and IL-6 levels and risk of MACE and all-cause death was assessed in proportional hazards models. RESULTS: A total of 11 817 patients had baseline hsCRP and IL-6 data; 1306 had a MACE primary endpoint and 458 died. Median hsCRP, IL-6, and low-density lipoprotein cholesterol (LDL-C) were 1.54 mg/L, 5.00 pg/ml, and 86 mg/dl, respectively. hsCRP and IL-6 had moderate correlation (r = 0.52). In models for one biomarker adjusted for the other biomarker, treatment assignment, age, sex, diabetes, LDL-C, and time since index ACS, hsCRP was a significant independent predictor of MACE (P < .0001) and IL-6 was not (P = .21); both independently predicted death (P < .0001 for hsCRP and P = .0003 for IL-6). Relationships did not depend on treatment (all Pinteraction > .25). When dichotomized at 2 mg/L (hsCRP) and 5 pg/ml (IL-6), risks of MACE and death were significantly elevated when both, but not when one marker was elevated. CONCLUSIONS: In patients with recent ACS, hsCRP independently predicted MACE, while both hsCRP and IL-6 predicted death. Together, the two markers provided complementary prognostic information. hsCRP conveys independent information on inflammatory risk beyond that provided by IL-6.