Clinical usefulness of very high and very low levels of C-reactive protein across the full range of Framingham Risk Scores.

BACKGROUND: High-sensitivity C-reactive protein (hsCRP) is a strong independent risk factor for cardiovascular events, and levels of hsCRP of <1, 1 to <3, and > or =3 mg/L have been suggested to define low-, moderate-, and high-risk groups. However, the positive predictive value of very low (<0.5 mg/L) and very high levels of hsCRP (>10.0 mg/L) is uncertain. METHODS AND
RESULTS: Baseline levels of hsCRP were evaluated among 27 939 apparently healthy women who were followed up for myocardial infarction, stroke, coronary revascularization, or cardiovascular death. Crude and Framingham Risk Score (FRS)-adjusted relative risks (RRs) of incident cardiovascular events were calculated across a full range of hsCRP levels. Cardiovascular risks increased linearly from the very lowest (referent) to the very highest levels of hsCRP. Crude RRs for those with baseline hsCRP levels of <0.5, 0.5 to <1.0, 1.0 to <2.0, 2.0 to <3.0, 3.0 to <4.0, 4.0 to <5.0, 5.0 to <10.0, 10.0 to <20.0, and > or =20.0 mg/L were 1.0, 2.2, 2.5, 3.1, 3.7, 4.2, 4.9, 6.3, and 7.6, respectively (P for trend <0.001). After adjustment for FRS, these risks were 1.0, 1.6, 1.6, 1.7, 1.9, 2.2, 2.3, 2.8, and 3.1 (P for trend <0.001). All risk estimates remained significant in analyses stratified by FRS and after control for diabetes. Of the total cohort, 15.1% had hsCRP <0.50 mg/L, and 5.4% had hsCRP >10.0 mg/L.
CONCLUSIONS: Both very low (<0.5 mg/L) and very high (>10 mg/L) levels of hsCRP provide important prognostic information on cardiovascular risk. hsCRP is clinically useful for risk prediction across a full range of values and across a full range of FRS.