LAUSR

BACKGROUND It is uncertain whether measurement of circulating total atherogenic lipoprotein particle cholesterol mass [non-HDL cholesterol (nonHDLc)] or particle concentration [apolipoprotein B (apo B) and LDL particle concentration (LDLp)] more accurately reflects risk of incident coronary heart disease (CHD). We evaluated CHD risk among women in whom these markers where discordant. METHODS Among 27533 initially healthy women in the Women's Health Study (NCT00000479), using residuals from linear regression models, we compared risk among women with higher or lower observed particle concentration relative to nonHDLc (highest and lowest residual quartiles, respectively) to individuals with agreement between markers (middle quartiles) using Cox proportional hazards models. RESULTS Although all 3 biomarkers were correlated (r ≥ 0.77), discordance occurred in up to 20.2% of women. Women with discordant high particle concentration were more likely to have metabolic syndrome (MetS) and diabetes (both P < 0.001). Over a median follow-up of 20.4 years, 1246 CHD events occurred (514725 person-years). Women with high particle concentration relative to nonHDLc had increased CHD risk: age-adjusted hazard ratio (95% CI) = 1.77 (1.56-2.00) for apo B and 1.70 (1.50-1.92) for LDLp. After adjustment for clinical risk factors including MetS, these risks attenuated to 1.22 (1.07-1.39) for apo B and 1.13 (0.99-1.29) for LDLp. Discordant low apo B or LDLp relative to nonHDLc was not associated with lower risk. CONCLUSIONS Discordance between atherogenic particle cholesterol mass and particle concentration occurs in a sizeable proportion of apparently healthy women and should be suspected clinically among women with cardiometabolic traits. In such women, direct measurement of lipoprotein particle concentration might better inform CHD risk assessment.