Cholesterol is necessary for the formation of cell membranes and is a component of the materials that render the skin waterproof. Cholesterol also contributes to the formation of bile salts, adrenocorticosteroids, estrogens, and androgens.

Cholesterol has two sources: (1) that obtained from the diet (exogenous cholesterol) and (2) that which is synthesized in the body (endogenous cholesterol). Although most body cells can form some cholesterol, most is produced by the liver and the intestinal mucosa. Because cholesterol is continuously synthesized, degraded, and recycled, it is probable that very little dietary cholesterol enters directly into metabolic reactions. Altered cholesterol levels are associated with a variety of disorders and also are affected by hormones and certain drugs (Table 5-13).

Note: Values for total cholesterol may vary according to the laboratory performing the test. In addition, values have been found to vary according to gender, race, income level, level of physical activity, dietary habits, and geographic location as well as in relation to age, as shown here.

• Ingestion of alcohol 24 hours before and food 12 hours before the test may falsely elevate levels.
• Ingestion of drugs known to alter cholesterol levels within 12 hours of the test may alter results, unless the test is being conducted to evaluate such effects (see Table 5-13).

• As a component of a complete physical examination, especially for individuals over age 40 years or those who are obese, or both, to estimate the degree of risk for atherosclerotic cardiovascular disease:
  • In general, the desirable blood cholesterol level is less than 200 mg/dL.
  • Cholesterol levels of 200 to 240 mg/dL are considered borderline, and the person is considered at high risk if other factors such as obesity and smoking are present; for the latter individuals, additional tests such as lipoprotein and cholesterol fractionation should be performed.
  • Cholesterol levels of greater than 250 mg/dL place the person at definite high risk for cardiovascular disease and require treatment; additional tests such as lipoprotein and cholesterol fractionation should be performed.
• Family history of hypercholesterolemia or cardiovascular disease or both
• Known or suspected disorders associated with altered cholesterol levels (see Table 5-13)
• Monitoring of response to dietary treatment of hypercholesterolemia and support for decisions regarding need for drug therapy (Cholesterol levels may fall with diet modification alone over a period of 6 months, only to return gradually to previous levels.)
• Monitoring for response to drugs known to alter cholesterol levels (see Table 5-13) or lipid-lowering agents

Nursing Care Before the Procedure

General client preparation is the same as that for any procedure involving collection of a peripheral blood sample (see Appendix I).

• For this test, the client should abstain from alcohol for 24 hours and from food for 12 hours before the study.
• Water is not restricted.
• It also is recommended that drugs that may alter cholesterol levels be withheld for 12 hours before the test, although this practice should be confirmed with the person ordering the study.

A venipuncture is performed and the sample collected in a red-topped tube. The sample should be sent promptly to the laboratory.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Resume food and any drugs withheld before the test.