ASSESSMENT OF CURRENT NATIONAL CHOLESTEROL EDUCATION-PROGRAM GUIDELINES FOR TOTAL CHOLESTEROL, TRIGLYCERIDE, HDL-CHOLESTEROL, AND LDL-CHOLESTEROL MEASUREMENTS

We examine the effect of systematic bias and random error, quality con trol, and intraperson biological variation on the National Cholesterol Education Program (NCEP) clinical classifications for reported lipid measurements. We consider misclassification to occur if a true lipid h omeostatic set point is within a desirable range but the reported lipi d value is in a high-risk range, or if a hue Lipid homeostatic set poi nt is in a high-risk range but the reported Lipid value is in a desira ble range. To evaluate the overall adequacy of the NCEP guidelines to ensure correct patient classification, we construct operating characte ristic curves for total cholesterol, triglycerides, high-density lipop rotein cholesterol, and low-density lipoprotein cholesterol. We demons trate that if laboratories are meeting the NCEP guidelines for inheren t bias and analytic precision and are using standard quality-control ( QC) procedures incorporating at least two QC samples per analytical ru n from each of two QC pools (for a total of 4 QC samples), the current NCEP guidelines are adequate to ensure (probability >0.90) correct pa tient classifications regardless of the size of the systematic bias of the laboratory or increased random analytic error. Thus we suggest th at at least two concentrations of QC material be included in the QC sc heme to ensure that the measurement system is operating within desired specifications across the entire range of desirable and high-risk lip id concentrations and to ensure with high probability that patients ar e correctly classified.