Hypolipoproteins and apolipoproteins are surface proteins of lipoprotein particles and are important in the study of atherosclerosis. Apolipoprotein A1 (Apo A1) is the main (90%) component of HDL. Apolipoprotein B (Apo B) is the main component of LDL and VLDL and is important in regulating cholesterol synthesis and metabolism.

This test is used to evaluate the risk for CAD. Apo A1 deficiencies are often associated with premature cardiovascular disease. Apo B plays an important role in LDL catabolism. The ratio of Apo A to Apo B correlates more closely with increased risk for CAD than do cholesterol levels or the LDL/HDL ratio. The lower the ratio, the higher the risk.

Apo A1:

• Men: 110–180 mg/dL or 1.1–1.8 g/L

• Women: 110–205 mg/dL or 1.1–2.0 g/L

Apo B:

• Men: 55–100 mg/dL or 0.55–1.00 g/L

• Women: 45–110 mg/dL or 0.45–1.10 g/L

Apo A1/Apo B Ratio:

• Men: lower risk: <0.7; average risk: 0.7–0.9; higher risk: >0.9

• Women: lower risk: <0.6; average risk: 0.6–0.8; higher risk: >0.8

1. Obtain a 5-mL venous blood sample (red-topped tube). Serum is needed.

2. Do not freeze the specimen. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

3. Fasting for 12 hours is needed.

1. Increased Apo A1 is associated with familial (inherited) hyper-α-lipoproteinemia.

2. Decreased Apo A1 is associated with the following conditions:

   1. Tangier disease (extremely low), hypo-α-lipoproteinemia

   2. β-Lipoproteinemia

   3. Apo C-II deficiency

   4. Apo A-I Milano disease

   5. Apo A-I–C-III deficiency

   6. Hypertriglyceridemia (familial)

   7. Poorly controlled diabetes

   8. Premature CAD

   9. Hepatocellular disease

   10. Nephrotic syndrome and kidney failure

3. Increased Apo B is associated with the following conditions:

   1. Hyperlipoproteinemia types IIa, IIb, and V

   2. Premature CAD Fredrickson type IIa

   3. Diabetes

   4. Hypothyroidism

   5. Nephrotic syndrome, kidney failure

   6. Hepatic disease and obstruction

   7. Dysglobulinemia

   8. Porphyria

   9. Cushing syndrome

   10. Werner syndrome (rare autosomal recessive progeroid syndrome, premature aging)

4. Decreased Apo B occurs with the following conditions:

   1. α-β-lipoproteinemia

   2. Hypo-α-lipoproteinuria (Tangier disease)

   3. Hypo-β-lipoproteinemia

   4. Type I hyperlipidemia

   5. Apo C-II deficiency

   6. Hypothyroidism

   7. Malnutrition/malabsorption

   8. Reye syndrome

Pretest Patient Care

1. Explain test purpose and procedure. A 12-hour fast is required, but water may be taken. Smoking is prohibited. Alcohol is prohibited.

2. Encourage relaxation.

3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. Decreased Apo A1 is associated with a diet high in polyunsaturated fats, smoking, and some drugs (see Appendix E).

2. Decreased Apo B is associated with a diet high in polyunsaturated fats and low-cholesterol diets and many drugs.

3. Increased apolipoprotein levels can be caused by various drugs.

4. Apolipoproteins are acute-phase reactants and should not be measured in ill patients (e.g., acute stress, burns, major illness, inflammatory diseases).