Abstract 3608: Lipoprotein (a) Cholesterol, But Not Lp(a) Mass, Is An Independent Predictor Of Angiographic Coronary Artery Disease And Subsequent Cardiovascular Events In Patients Referred For Coronary Angiography.
Background: Elevated plasma levels of Lipoprotein (a) [Lp(a)] have been associated with increased risk for coronary artery disease (CAD) and cardiovascular (CV) events, but the association remains controversial. Differences in prospective studies may be partially explained by a lack of standardization of methods used to measure Lp(a) protein mass. Lp(a) mass and Lp(a) cholesterol were measured to determine the predictive value of each in assessing angiographic CAD and subsequent CV events.
Methods: Lp(a) cholesterol was measured by electrophoresis and enzymatic staining of cholesterol in separated Lp(a) particles (Helena Laboratories). Lp(a) mass levels were measured using an automated immunoturbidimetric method (Polymedco). Measures were obtained in 504 patients undergoing clinically indicated angiography.
Results: Median follow-up for events was 4.0 years and 58 CV events were observed in 49 of 466 contacted patients. Elevated Lp(a) cholesterol and Lp(a) mass were significantly associated with extent of angiographic CAD (P < 0.001). High Lp(a) cholesterol was also significantly associated with CV events (p= 0.01), while high Lp(a) mass approached but did not reach statistical significance (P=0.06). In a multiple regression analysis model adjusting for age, gender, LDL cholesterol, HDL, triglyceride, Lp(a) mass, and Lp(a) cholesterol; Lp(a) cholesterol remained a significant predictor of angiographic CAD (OR 1.54, 95% CI 1.24 –1.91, P <.001) and CV events (OR 1.34, 95% CI 1.06 –1.67, P = 0.01), while Lp(a) mass was no longer significantly associated with CAD (p=0.96) or events (p=0.28). Measurement of Lp(a) isoform size in selected patient samples (n=94) using western blotting revealed that the discrepancy between methods is due at least in part to the influence of isoform size on Lp(a) mass measures. Lp(a) cholesterol measures are not influenced by isoform size.
Conclusions: Lp(a) cholesterol was a strong independent predictor for angiographic CAD and CV events. Lp(a) cholesterol was a better predictor of angiographic CAD and events than was immunologic Lp(a) mass measurement. Lp(a) Cholesterol measurement may be used in the clinical laboratory as a more specific alternative to Lp(a) mass analysis for cardiovascular risk assessment.