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Introduction ⬇

Alpha-1 (α1) Antitrypsin (AAT); α1-Antitrypsin; A1A

Alpha-1 (α1) antitrypsin (AAT) is a protein produced by the liver that inhibits the protease released into body fluids by dying cells. This protein deficiency is associated with pulmonary emphysema and liver disease, both at an early age. Human serum contains at least three inhibitors of protease. Two of the best known are AAT and α2-macroglobulin. Total antitrypsin levels in blood are composed of about 90% AAT and 10% α2-macroglobulins.

This is a nonspecific method to diagnose inflammation, severe infection, and necrosis. AAT measurement is important for diagnosing respiratory disease and cirrhosis of the liver because of its direct relation to pulmonary and other metabolic disorders. Pulmonary problems such as emphysema occur when persons with antitrypsin deficiency are unable to ward off the action of endoproteases. Those who are deficient in AAT develop emphysema at a much earlier age than do other emphysema patients.

Normal Findings ⬆ ⬇

Adults: 110–200 mg/dL or 1.1–2.0 g/L

If result is <125 mg/dL (<1.25 g/L), phenotype should be determined to confirm homozygous and heterozygous deficiencies.

Newborn: 145–270 mg/dL or 1.45–2.70 g/L

Procedure ⬆ ⬇

  1. Obtain a 1-mL serum sample. Use a red-topped SST.

  2. Observe standard precautions. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

Clinical Implications ⬆ ⬇

  1. Interpretation of AAT levels is based on the following:

    1. High levels are generally found in normal persons.

    2. Intermediate levels are found in persons with a predisposition to pulmonary emphysema.

    3. Low levels are found in persons with obstructive pulmonary disease and in children with cirrhosis of the liver.

  2. Increased AAT levels occur in the following conditions:

    1. Acute and chronic inflammatory disorders

    2. After injections of typhoid vaccine

    3. Cancer

    4. Thyroid infections

    5. Oral contraceptive use

    6. Stress syndrome

    7. Hematologic abnormalities

    8. Pregnancy

  3. Decreased AAT levels are associated with these progressive diseases:

    1. Adult, early-onset, chronic pulmonary emphysema

    2. Liver cirrhosis in infants (neonatal hepatitis)

    3. Pulmonary disease

    4. Severe hepatic damage

    5. Nephrotic syndrome

    6. Malnutrition

Clinical Alert

Patients with serum levels 70 mg/dL (0.70 g/L) are at risk for early lung disease and should be monitored

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure. Fasting is required.

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

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Advise patients with decreased levels to avoid smoking and, if possible, occupational hazards such as dust, fumes, and other respiratory pollutants.

  2. Because AAT deficiencies are inherited, genetic counseling may be indicated. Follow-up AAT phenotype testing can be performed on family members to determine the homozygous or heterozygous nature of the deficiency.

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

Interfering Factors ⬆

AAT in an acute-phase reactant and any inflammatory process will elevate serum levels.