Background: Serum amyloid-alpha (SAA) is a sensitive marker of an acute inflammatory state. Like high-sensitivity C-reactive protein (hs-CRP), SAA has been linked to atherosclerosis. However, prior studies have yielded inconsistent results, and the independent predictive value of SAA for coronary artery disease (CAD) severity and cardiovascular events remains unclear.
Methods and results: A total of 705 women referred for coronary angiography for suspected myocardial ischemia underwent plasma assays for SAA and hs-CRP, quantitative angiographic assessment, and follow-up evaluation. Cardiovascular events were death, myocardial infarction, congestive heart failure, stroke, and other vascular events. The women's mean age was 58 years (range 21 to 86 years), and 18% were nonwhite. SAA and hs-CRP were associated with a broad range of CAD risk factors. After adjustment for these risk factors, SAA levels were independently but moderately associated with angiographic CAD (P=0.004 to 0.04) and highly predictive of 3-year cardiovascular events (P<0.0001). By comparison, hs-CRP was not associated with angiographic CAD (P=0.08 to 0.35) but, like SAA, was strongly and independently predictive of adverse cardiovascular outcome (P<0.0001).
Conclusions: Our results show a strong independent relationship between SAA and future cardiovascular events, similar to that found for hs-CRP. Although SAA was independently but moderately associated with angiographic CAD, this association was not found for hs-CRP. These results are consistent with the hypothesis that systemic inflammation, manifested by high SAA or hs-CRP levels, may promote atherosclerotic plaque destabilization, in addition to exerting a possible direct effect on atherogenesis.