Lipoprotein-associated phospholipase A2 activity improves risk discrimination of incident coronary heart disease among women.

BACKGROUND: This study sought to determine the relation between and discriminative capability of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) and coronary heart disease (CHD) in a large population of disease-free women. METHODS: Among participants of the Nurses' Health Study who provided a blood sample, there were 421 cases of incident myocardial infarction during 14 years of follow-up. Controls were matched to cases 2:1 using risk set sampling based on age, smoking, and blood draw date. RESULTS: After conditioning on the matching factors, Lp-PLA(2) activity was significantly associated with myocardial infarction (relative risk [RR] 2.86 for extreme quartiles, 95% CI 1.98-4.12). Upon additional adjustment for lipid, inflammatory, and clinical risk factors, the RR remained statistically significant (RR 1.75, 95% CI 1.09-2.84). The discriminative capability of Lp-PLA(2) was assessed by comparing the area below the receiver operating characteristic curves for models with and without Lp-PLA(2) and by calculating the net reclassification improvement index. The addition of Lp-PLA(2) activity to a multivariable-adjusted model increased the receiver operating characteristic curves from 0.720 to 0.733 and significantly improved the net reclassification improvement index (P = .004). CONCLUSIONS: Levels of Lp-PLA(2) activity were significantly associated with incident CHD among women. In addition, Lp-PLA(2) activity added significantly to CHD risk discrimination.