Alpha1-Antitrypsin Test (AAT)

Test Description

Alpha1-antitrypsin (AAT) is a protein produced by the liver. It has a protective function,

in that it prevents the release of proteolytic enzymes that can damage tissues                   

such as that of the lung. AAT deficiency can be inherited or acquired. When an              

inherited problem, AAT deficiency is most often noted in individuals of                          

European descent and is first noted relatively early in life. Acquired AAT deficiency     

is seen in patients who have protein-deficiency syndromes such as liver disease,            

nephrotic syndrome, and malnutrition. Regardless of the type, the deficiency of AAT    

allows proteolytic enzymes to damage lung tissue, resulting in severe emphysema         

in young adulthood.

THE EVIDENCE FOR PRACTICE

Alpha1-antitrypsin (AAT) deficiency accounts for less than one percent of cases of chronic

obstructive pulmonary disease (COPD). However, it may be suspected and an AAT level

obtained in patients with moderate-severe COPD before the age of 50, a family history of

AAT, chronic bronchitis with airflow obstruction in a person who has never smoked,

bronchiectasis in the absence of clear risk factors, or cirrhosis without apparent risk

factors.

Normal Values

85–213 mg/dL (20–60 μmol/L SI units)

Possible Meanings of Abnormal Values

Increased                                                                   Decreased                                            

Acute inflammatory disorders                                 AAT deficiency

Cancer                                                                      Chronic liver disease

Chronic inflammatory disorders                              Emphysema

Chronic liver disease                                               Malnutrition

Hepatitis                                                                   Nephrotic syndrome

Infection                                                                   Severe hepatic damage

Pregnancy

Stress

Systemic lupus erythematosus (SLE)

Thyroid infection

Contributing Factors to Abnormal Values

• Drugs that may increase AAT levels: estrogens, oral contraceptives, steroids.

     Interventions/Implications

   Pretest 

• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.

• No fasting is required before the test unless the patient has hyperlipidemia. If so, the

patient should fast 8 to 10 hours before the test.

Procedure

• A 7-mL blood sample is drawn in a red-top collection tube.

• Gloves are worn throughout the procedure.

Post test

• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued

  bleeding.

• Label the specimen and transport it to the laboratory.

• Report abnormal findings to the primary care provider

Clinical alert                                                                                                          

• Patients who are AAT deficient need to be taught to avoid smoking and employment

   in occupations in which air pollutants are common.

• Genetic counseling should be offered to patients with positive test results.

   Testing of other family members should also be conducted.