2005, Volume 16, Number 1
By David F. Keren, MD
Background on CRP
For several decades, CRP has been the most reliable marker of early inflammation. It is a hepatocyte-derived, 135 kDa protein that increases quickly to levels above 5 mg/L (when the standard CRP assay is used) in patients with acute inflammation. The name, C-reactive protein derives from the fact that it reacts with the capsular polysaccharide of Streptococcus pneumoniae.
hs-CRP and cardiovascular risks
In the past few years, several studies have shown that a new, much more sensitive assay (hs-CRP) for detecting low quantities of CRP can identify patients who are at increased risk for recurrent cardiovascular disease and stroke, or death in a variety of clinical situations. Recent work further indicates that higher levels of hs-CRP can be used to predict which patients are most likely to have vessels opened by balloon angioplasty reclose.
By dividing the level of hs-CRP into thirds (<1.0 mg/L, 1.0-3.0 mg/L, and >3.0 mg/L), studies have shown that individuals who have >3.0 mg/L are twice as likely to develop a heart attack as those who have values <1.0 mg/L.
As far as cardiovascular risk is concerned, in patients with acute coronary syndrome hs-CRP values >10 mg/L within 6-24 hours after the onset of symptoms may indicate increased risk for recurrent cardiac events within 30 days to 1 year. Further, in patients with unstable angina, hs-CRP values >10 mg/L may predict a higher rate of myocardial infarction or mortality than in patients with hs-CRP <10 mg/L.
American Heart Association/Centers for Disease Control Recommendation
In performing studies on hs-CRP, however, one should also recall that levels can also increase greatly in individuals who have acute inflammation not related to cardiovascular risk.
Because of this, the American Heart Association and the Centers for Disease Control recommend that “if after repeat testing, patients have persistently unexplained, marked elevated hs-CRP levels (>10.0 mg/L), other evaluations should be considered to exclude noncardiovascular causes.”
- Pearson, TA, et al. Markers of inflammation and cardiovascular disease application to clinical and public health practice. A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation 2003;107:499-511.
- Heeschen, C et al. Predictive value of C-reactive protein and troponin T in patients with unstable angina. A comparative analysis. J Am Coll Cardiol 1000;35:1535-42.
- Skowasch, D et al. Progression of native coronary plaques and in-stent restenosis are associated and predicted by increased pre-procedural C-reactive protein. Heart 2005;91:535-6.