31Cholesterol

High blood cholesterol is an important modifiable risk factor for coronary heart disease (CHD) -- the leading cause of death for both men and women in the United States. This year, as many as 1.5 million Americans will have a new or recurrent myocardial infarction, and about one third of these individuals will die. Large, population-based studies have demonstrated that total cholesterol levels are directly related to the incidence of CHD. The Multiple Risk Factor Intervention Trial (MRFIT) found that the 6-year risk of death from CHD in normotensive, nonsmoking, middle-aged men with blood cholesterol levels less than 182 mg/dL was one fourth that of men with blood cholesterol levels of 245 mg/dL or higher. An analysis of 22 epidemiologic studies has shown that elevated cholesterol is also a risk factor for CHD in women and in individuals > 65 years of age. Epidemiologic studies have also shown that cholesterol lipoprotein subfractions play an important role in CHD. LDL-cholesterol is directly, and HDL-cholesterol is inversely, associated with the incidence of CHD.

No long-term study has compared interventions to reduce cholesterol levels and CHD incidence based on routine cholesterol screening with interventions based on selective case-finding or with universal dietary advice. Because the recent increase in cholesterol screening had been accompanied by an improved knowledge and public awareness of dietary risk factors, isolating the contribution of screening from other factors that may account for improved outcomes may be difficult. The major evidence to support cholesterol screening is the ability of cholesterol-lowering interventions to reduce the risk of CHD in patients with high cholesterol.

A meta-analysis of cholesterol-lowering trials performed mainly in middle-aged men found that lowering blood cholesterol levels through dietary management or drug therapy significantly reduces the risk of CHD death and nonfatal myocardial infarction. The West of Scotland Coronary Prevention Study Group, a primary prevention trial, showed a reduction in cardiovascular mortality associated with drug treatment with no difference between treatment groups in the rate of death due to noncardiovascular causes. Similarly, the Scandinavian Simvastatin Survival Study, a secondary prevention trial, showed that in patients with a history of myocardial infarction, the reduction in CHD mortality associated with drug treatment was accompanied by a reduction in total mortality.

See chapter 4 for information on cholesterol screening for children and adolescents.

Recommendations of Major Authorities

  • American Academy of Family Physicians --
  • Males aged 35 to 65 years and females aged 45 to 65 years should be screened periodically for high cholesterol levels.
  • American College of Obstetricians and Gynecologists --
  • Adults (19 years of age and older) should have cholesterol measured every 5 years until 64 years of age, then every 3 to 5 years thereafter. (These are currently under review for a possible change to recommendations consistent with the US Preventive Services Task Force.)
  • American College of Physicians --
  • Screening for total cholesterol in the primary prevention of CHD is appropriate but not mandatory in men between 35 and 65 years of age and for women between 45 and 65 years of age. Screening for total cholesterol is not recommended for men younger than 35 years of age or women younger than 45 years of age unless the history or physical examination suggests a familial lipoprotein disorder, or at least two other characteristics place them at increased risk for developing CHD. There is insufficient evidence to recommend for or against screening in men and women between the ages of 65 and 75. Screening of individuals over 75 years of age is not recommended. In those individuals who are screened for the primary prevention of CHD, the total cholesterol level should be measured once. It should be repeated periodically if the measured value is near a treatment threshold. All patients with known CHD or whose history of other kinds of vascular disease places them at very high risk of CHD should have measurements of total cholesterol.
  • Canadian Task Force on the Periodic Health Examination --
  • There is insufficient evidence for the inclusion or exclusion of universal screening for hypercholesterolemia in a periodic health examination. Nonetheless, case-finding through repeated measurements of the nonfasting total blood cholesterol level should be considered in men 30 to 59 years of age.
  • National Cholesterol Education Program (NCEP) of the National Heart, Lung, and Blood Institute --
  • Adults (20 years of age and older) should have a measurement of total blood cholesterol at least once every 5 years; HDL-cholesterol should be measured at the same time if accurate results are available. Lipoprotein analysis should be performed for all patients with CHD. In patients without CHD, lipoprotein analysis should be performed in any of the following circumstances: (1) if the total cholesterol is 240 mg/dL or above; (2) if the total cholesterol is 200 to 239 mg/dL and the patient also has two or more CHD risk factors; (3) if the patient has an HDL-cholesterol less than 35 mg/dL. See Tables 31.1 and 31.2 and Figures 31.1, 31.2, and 31.3 for NCEP recommendations on CHD risk factors and patient classification and identification.
Table 31.1. NCEP Coronary Heart Disease Risk Factors Other Than LDL-Cholesterol *.

Table

Table 31.1. NCEP Coronary Heart Disease Risk Factors Other Than LDL-Cholesterol *.

Table 31.2. Treatment Decisions Based on LDL-Cholesterol.

Table

Table 31.2. Treatment Decisions Based on LDL-Cholesterol.

Figure 31.1. Primary Prevention in Adults Without Evidence of CHD: Initial Classification Based on Total Cholesterol and HDL-Cholesterol.

Figure

Figure 31.1. Primary Prevention in Adults Without Evidence of CHD: Initial Classification Based on Total Cholesterol and HDL-Cholesterol. Adapted from: National Cholesterol Education Program. Second Report of the National Cholesterol (more...)

Figure 31.2. Primary Prevention in Adults Without Evidence of CHD: Subsequent Classification Based on LDL-Cholesterol.

Figure

Figure 31.2. Primary Prevention in Adults Without Evidence of CHD: Subsequent Classification Based on LDL-Cholesterol. *On the basis of the average of two determinations. If the first two LDL-cholesterol levels differ by more than 30 (more...)

Figure 31.3. Secondary Prevention in Adults With Evidence of CHD: Classification Based on LDL-Cholesterol.

Figure

Figure 31.3. Secondary Prevention in Adults With Evidence of CHD: Classification Based on LDL-Cholesterol. *Perform lipoprotein analysis when the patient is not in the recovery phase from an acute coronary or other medical event that (more...)

  • US Preventive Services Task Force --
  • Periodic screening for high serum cholesterol is recommended for all men 35-65 years of age and women 45-65 years of age. There is insufficient evidence to recommend for or against screening asymptomatic persons after 65 year of age, but screening may be considered on a case-by-case basis. Older persons with major CHD risk factors (smoking, hypertension, diabetes) who are otherwise healthy may be more likely to benefit from screening, based on their high risk of CHD and the proven benefits of lowering cholesterol in older persons with symptomatic CHD. Cholesterol levels are not a reliable predictor of risk after age 75, however. There is also insufficient evidence to recommend for or against screening of young adults, although this may be recommended on other grounds to young adults at high risk, such as the greater absolute risk attributable to high cholesterol and potential long-term benefits of early lifestyle interventions. Risk factors include: family history of very high cholesterol, premature CHD in a first-degree relative (before age 50 in men or age 60 in women), diabetes, smoking, or hypertension. The appropriate interval for periodic screening is not known. Periodic screening is most important when cholesterol levels are increasing (eg, middle-aged men, perimenopausal women, and persons who have gained weight). An interval of five years has been recommended by experts, but longer intervals may be reasonable for low-risk subjects (including those with previously desirable cholesterol levels). There is insufficient evidence to recommend for or against routine measurement of HDL-cholesterol or triglycerides at initial screening.

Basics of Cholesterol Screening

1.

Do not screen patients who are acutely ill, losing weight, pregnant, or breast-feeding, because their cholesterol levels may not be representative of their usual levels. Cholesterol levels in patients who have had a myocardial infarction within the past 3 months are likely to be lower than usual. Therefore, recheck any results obtained during this period.

2.

Inform patients that they need not vary their usual eating habits before undergoing screening for total blood cholesterol or HDL-cholesterol levels. Instruct patients undergoing lipoprotein analysis to fast for 12 hours before testing. Water and black coffee are acceptable, however.

3.

If possible, perform cholesterol tests on venous blood samples, because cholesterol concentrations measured from finger-stick blood samples may be unreliable. The NCEP cut-off values for diagnostic and therapeutic actions refer to venous serum samples.

4.

To prevent an effect of posture or stasis on the cholesterol value, perform venipuncture only after the patient has been in the sitting position for at least 5 minutes; apply the tourniquet for as brief a period as possible.

5.

When interpreting results, be aware of the effects of medications on blood cholesterol levels. Anabolic steroids, progestins, bile salts, and chlorpromazine increase blood cholesterol levels. Be knowledgeable about conditions that may cause increased cholesterol levels, such as hypothyroidism, nephrotic syndrome, diabetes mellitus, and obstructive liver disease.

6.

Cholesterol tests should be analyzed by an accredited laboratory that meets current standards for precision and accuracy. The Laboratory Standardization Panel of the National Cholesterol Education Program has set a goal that laboratories have systematic and precision errors of less than 3% each in processing total cholesterol samples. Inquire about a laboratory's performance history and its quality-control methods before using it for screening.

7.

Cholesterol values in plasma samples tend to be lower than serum samples because of the effects of EDTA in plasma samples. NCEP has determined cholesterol level cut-off values based on serum samples and has designated that cholesterol levels obtained from plasma samples be multiplied by 1.03 to arrive at a serum equivalent.

8.

Convert cholesterol values in mg/dL to mmol/L by multiplying by 0.02584. Convert triglyceride levels similarly by multiplying by 0.01129.

9.

See Table 56.3 for information about NCEP's Step I and Step II Diet for treatment of patients with elevated cholesterol levels.

10.

Provide dietary and weight-reduction counseling to all patients who are obese, regardless of their cholesterol levels (chapters 29 and 56). Provide advice about increasing physical activity to all patients who are physically inactive, regardless of their cholesterol levels (chapter 57).

Table 56.3. Examples of Foods To Choose or Decrease for the NCEP Step I and Step II Diets *.

Table

Table 56.3. Examples of Foods To Choose or Decrease for the NCEP Step I and Step II Diets *.

Patient Resources

  • Cholesterol: What You Can Do to Lower Your Level. American Academy of Family Physicians, 8880 Ward Parkway, Kansas City, MO 64114-2797; (800)944-0000; http://www.aafp.org
  • Cholesterol and Your Health. American College of Obstetricians and Gynecologists, 409 12th St, SW, Washington, DC 20024-2188; (800)762-2264. Internet address: http://www.acog.com
  • Cholesterol and Your Heart; Dietary Treatment of Hypercholesterolemia: A Manual for Patients; Eat Less Fat and High Cholesterol Foods; Heart Rx (a kit of materials for patients, providers, and staff). To order these and many other materials, contact the American Heart Association, 7320 Greenville Ave, Dallas, TX 75231. To receive the telephone number of your state office, call the main office at: (800)242-8721; materials vary by state. Internet address: http://www.amhrt.org
  • American Heart Association Low-Fat, Low-Cholesterol Cookbook. This publication is available at retail bookstores. Internet address: http://www.amhrt.org
  • Eat Right to Lower Your High Blood Cholesterol and Step by Step: Eating to Lower Your High Blood Cholesterol; So You Have High Blood Cholesterol. National Heart, Lung, and Blood Institute Information Center, PO Box 30105, Bethesda, MD 20824-0105; (301)251-1222. Internet address: http://www.nhlbi.nih.gov/nhlbi/nhlbi.htm. Information is available in both English and Spanish. The following materials are available in Spanish: Learn Your Cholesterol Number (Conozca su nivel de colesterol); Protect Your Health-Lower Your Blood Cholesterol (Proteja su corazon-baje su colesterol); and Heart-Healthy Latino Recipes (Platillos Latinos).

Provider Resource

  • Summary of the Second Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II). Full report: National Cholesterol Education Program: Second Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II). National Heart, Lung, and Blood Institute Information Center, PO Box 30105, Bethesda, MD 20824-0105; (301)251-1222. Information is available in both English and Spanish. Internet address: http://www.nhlbi.nih.gov/nhlbi/nhlbi.htm

Selected References

  1. American Academy of Family Physicians. Summary of Policy Recommendations for Periodic Health Examination . Kansas City, Mo: American Academy of Family Physicians; 1997.
  2. American College of Obstetricians and Gynecologists. Guidelines for Women's Health Care . Washington, DC: American College of Obstetricians and Gynecologists; 1996.
  3. American College of Physicians, Clinical Efficacy Assessment Project. Using serum cholesterol, high-density lipoprotein cholesterol, and triglycerides as screening tests for the prevention of coronary heart disease in adults. Ann Intern Med. In press.
  4. American College of Physicians. Guidelines. In: Eddy DM, ed. Common Screening Tests. Philadelphia, Pa: American College of Physicians; 1991:402-403.
  5. American Heart Association. Heart and Stroke Facts: 1996 Statistical Supplement. Dallas, TX: American Heart Association; 1995.
  6. Canadian Task Force on the Periodic Health Examination. Lowering the total blood cholesterol level to prevent coronary heart disease. In: The Canadian Guide to Clinical Preventive Health Care. Ottawa, Canada: Minister of Supply and Services; 1994: chap 54.
  7. Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Summary of the second report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II) JAMA . 1993; 269:3015–3023. [PubMed: 8501844]
  8. Greenland P, Bowley NL, Meiklejohn B, Doane KL, Sparks CE. Blood cholesterol concentration: fingerstick plasma vs venous serum sampling. Clin Chem . 1990; 36:628–630. [PubMed: 2323042]
  9. National Cholesterol Education Program. Second Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II) Bethesda, Md: National Heart, Lung, and Blood Institute. 1993. The full Adult Treatment Panel II report is also available in Circulation. 1994; 89:1329–1445.
  10. National Cholesterol Education Program. Report of the Expert Panel on Population Strategies for Blood Cholesterol Reduction . Bethesda, Md: National Institutes of Health, National Heart, Lung, and Blood Institute; 1990. US Dept of Health and Human Services, PHS publication NIH 90-3046.
  11. NIH Consensus Development Panel on Triglyceride, High-Density Lipoprotein, and Coronary Heart Disease. Triglyceride, high-density lipoprotein, and coronary heart disease. JAMA . 1993; 269:505–510. [PubMed: 8419671]
  12. Sempos CT, Cleeman JI, Carroll MD, et al. Prevalence of high blood cholesterol among US adults: an update based on guidelines from the second report of the National Cholesterol Education Program Adult Treatment Panel. JAMA . 1993; 269:3009–3014. [PubMed: 8501843]
  13. Shepherd J, Cobbe SM, Ford I, et al. Prevention of coronary heart disease with pravastatin in men with hypercholesterolemia. N Engl J Med . 1995; 333:1301–7. [PubMed: 7566020]
  14. US Preventive Services Task Force. Screening for blood cholesterol.In: Guide to Clinical Preventive Services. 2nd ed. Washington, DC: US Department of Health and Human Services; 1996: chap 2.