ESSENTIALS OF DIAGNOSIS
Serum cholesterol values greater than ideal for the prevention of atherosclerotic cardiovascular disease (ASCVD).
Patients with clinical ASCVD or low-density lipoprotein (LDL) cholesterol ≥190 mg/dL, diabetic patients age 40–75, or those with an elevated 10-year risk for ASCVD require treatment.
The Framingham Heart Study firmly established an epidemiologic link between elevated serum cholesterol and an increased risk of morbidity and mortality from ASCVD. Although the benefits of lowering cholesterol were assumed for many years, not until 2001 had enough evidence accumulated to show unequivocal benefits from using lifestyle and pharmacologic therapy to lower serum cholesterol. Evidence in support of using statin agents is particularly strong and has revolutionized the treatment of dyslipidemias.
The efficacy of lipid reduction for the secondary prevention of ASCVD (reducing further disease-related morbidity in those with manifest disease) is supported by multiple trials and is appropriate in all patients with ASCVD. The efficacy of primary prevention (reducing the risk of disease occurrence in those without overt cardiovascular disease) is now supported by growing evidence that has been reviewed by the Cochrane Collaboration and led to 2016 guidelines for primary prevention from the US Preventive Services Task Force (USPSTF). The USPSTF now endorses the use of statins in adults age 40–75 years with a calculated 10-year risk of 10% or greater.
The American College of Cardiology (ACC) and American Heart Association (AHA) released new integrated guidelines for cardiovascular disease reduction in 2013. These guidelines emphasize aggressive treatment of dyslipidemias and other cardiovascular risk factors with lifestyle interventions and targeted use of statin medications, with the intensity of treatment titrated to the patients risk status. These guidelines form the foundation for the approach to the treatment of dyslipidemias.
Serum cholesterol is carried by three major lipoproteins: high-density lipoprotein (HDL), LDL, and very-low-density lipoprotein (VLDL). All clinical laboratories can measure the total cholesterol, total triglycerides (TG), and the HDL fraction, and most can now directly measure the LDL fraction.
The triglyceride fraction and, to a lesser extent, the HDL level vary considerably depending on the fasting status of the patient. The ACC/AHA guidelines recommend that fasting measurements of total cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol be used to guide management decisions unless a direct measure of LDL cholesterol is available.
Different populations have different median cholesterol values. For example, Asian populations tend to have total cholesterol values 20–30% lower than those of populations living in Europe or the United States. It is important to recognize that unlike a serum sodium electrolyte value, there is no normal cholesterol value. Instead, there are cholesterol values that predict higher morbidity and mortality from ASCVD if left untreated and lower cholesterol values that correlate with less likelihood of cardiovascular disease.
Atherosclerosis is an inflammatory ...