Interleukin-1 receptor antagonist: A sensitive marker of instability in patients with coronary artery disease

Background: Increased plasma levels of acute phase reactants are correlated with acute coronary syndromes and increased risk of in-hospital events. Interleukin-1 receptor antagonist (IL-IRa) modulates the activity of IL-1, a cytokine associated with inflammatory response; we have prospectively investigated whether detection of increased levels of IL-IRa in patients may be useful in the characterization of coronary syndromes. Methods: Plasma levels of IL-IRa were measured in 118 consecutive patients undergoing coronary angiography with a clinical diagnosis of recent unstable angina (N = 57), chronic stable angina (N= 49) or atypical chest pain (N= 12). Results: Angiography showed significant coronary disease in the first two groups and was normal in the latter group. Patients with unstable angina had significantly higher levels of IL-IRa than stable patients [158 (110-224) vs 108 (95-154) pg/ml, P = 0.002] and individuals with chest pain and normal coronary angiogram [110 (97-123) pg/ml, P = 0.038]. In contrast, while C-reactive protein levels were significantly higher in patients with stable and unstable angina vs those without coronary disease (0.29 vs 0.06 mg/dl, P = 0.022), they did not discriminate between stable and unstable angina patients (0.22 vs 0.32 mg/dl, P = 0.66). Conclusions: These results indicate that IL-IRa may be a sensitive marker of clinical instability in patients with coronary artery disease.