Plasma biomarkers were measured for nonfatal MI and fatal CHD cases and their controls. C-reactive protein concentrations were determined using an immunoturbidimetric high sensitivity assay using reagents and calibrators from Denka Seiken (Niigata, Japan) with assay day-to-day variability between 1 and 2%. This assay has a sensitivity of 0.1 mg/L, and the day-to-day variability of the assay at concentrations of 0.91, 3.07, and 13.38 mg/L were 2.8, 1.6, and 1.1%, respectively. The intra-assay coefficients of variation were <10% for both HPFS and NHS. Total, HDL, and directly assessed LDL cholesterol, and triglycerides were measured using standard methods with reagents from Roche Diagnostics (Indianapolis, IN) and Genzyme (Cambridge, MA). Study samples were sent to the laboratory for analysis in randomly ordered batches, and the laboratory was blinded to case-control status.
