DIRECT MEASUREMENT OF SERUM LOW-DENSITY-LIPOPROTEIN CHOLESTEROL IN PATIENTS WITH ACUTE MYOCARDIAL-INFARCTION ON ADMISSION TO THE EMERGENCY ROOM

In most clinical laboratories low-density lipoprotein (LDL) levels are estimated by use of a mathematic formula, the Friedewald equation, ra ther than measured directly.(1) Although the Friedewald estimate is re liable when the triglyceride level is <400, it is influenced by the fe d or fasting state. Postprandial elevation of triglycerides is respons ible for lowering LDL levels by the Friedewald estimate: 7% reduction of LDL 2 hours after a meal and 2.5% reduction of LDL 5 hours after a meal.(2) Lipid measurement during an acute myocardial infarction prese nts a number of problems to clinicians wanting to address secondary pr evention of disease: Lipid measurements are accurate only in the first 24 hours after the event, and patients are usually admitted to hospit als in the nonfasting state.(3) In addition, the triglyceride level ma y be elevated 25% over the baseline or preinfarction level early after myocardial infarction and may also yield falsely lower estimates of L DL cholesterol levels.(3) LDL cholesterol may be directly measured in nonfasting patients with the ultracentrifuge. Ultracentrifugation is a technically demanding procedure requiring 48 hours of preparation inv olving the analytic ultracentrifuge, a piece of equipment not usually found in most clinical laboratories.(4) In addition to ultracentrifuga tion, the newly developed immunoseparation method of LDL measurement 5 does not require a fasting specimen, may be performed in 3 hours, and is easier to use technically, The following study compares immunosepa ration, ultracentrifugation, and the Friedewald estimate of LDL in pat ients admitted to the hospital for treatment of an acute myocardial in farction.