Direct assessment of plasma low density lipoprotein and high density lipoprotein cholesterol levels and coronary heart disease: results from the Framingham Offspring Study.

Background: We evaluated direct low density lipoprotein (LDL) cholesterol (C) and high density lipoprotein (HDL) cholesterol (C) versus standard methods using fasting plasma samples from participants in cycle 6 of the Framingham Offspring Study.

Methods: Direct LDL-C and HDL-C measurements were performed on fasting plasma from male (1335 controls, 173 CHD cases) and female (1606 controls, 74 cases) participants, and compared with LDL-C, as calculated with the Friedewald formula, and HDL-C, as measured after dextran-Mg(2+) precipitation.

Results: Values for direct LDL-C and HDL-C correlated well with standard methods (both about r(2)=0.94, p<0.001) with similar absolute values. Biases of >10% were present for 7.7% of samples for LDL-C, while for HDL-C this value was 8.5%. Despite higher use of cholesterol-lowering medication in CHD cases, calculated or direct LDL-C values were still well above recommended values [<2.6 mmol/L (100 mg/dL)] in CHD cases, especially in females.

Conclusions: Direct assays for both LDL-C and HDL-C provide an acceptable guide for lipid treatment. In Framingham Offspring Study participants most CHD cases had LDL-C levels above the recommended target.