Alpha1-Antitrypsin and Alpha1-Antitrypsin Phenotyping
Synonym/Acronym
Alpha1-antitrypsin: A1 AT, alpha1-AT, AAT; alpha1-antitrypsin phenotyping: A1 AT phenotype, alpha1-AT phenotype, AAT phenotype, Pi phenotype.
Rationale
To assist in the identification of chronic obstructive pulmonary disease (COPD) and liver disease associated with alpha1-antitrypsin (alpha1-AT) deficiency.
Patient Preparation
There are no food, fluid, or activity restrictions unless by medical direction. Oral contraceptives should be withheld 24 hr before the specimen is collected, although this restriction should first be confirmed with the health-care provider (HCP) ordering the test.
Normal Findings
Method: Nephelometry for alpha1-AT, isoelectric focusing/high-resolution electrophoresis for alpha1-AT phenotyping.
Alpha1-Antitrypsin
| Age | Conventional Units | SI Units (Conventional Units × 0.01) |
|---|
| Newborn | 145–270 mg/dL | 1.45–2.7 g/L | | Child | 110–157 mg/dL | 1.1–1.579 g/L | | Adult | 100–190 mg/dL | 1–1.9 g/L |
|
Alpha1-Antitrypsin Phenotyping
There are three major protease inhibitor phenotypes:
- MM—Normal
- SS—Intermediate; heterozygous
- ZZ—Markedly abnormal; homozygous
The total level of measurable alpha1-AT varies with genotype. The effects of alpha1-AT deficiency depend on the patient’s personal habits but are most severe in patients who smoke tobacco.
Study type: Blood collected in a gold-, red-, red/gray-, or lavender-top [EDTA] tube; related body system: Digestive and Respiratory systems.
Alpha1-AT is the main glycoprotein produced by the liver. Elevated levels are found in normal individuals when an inflammatory process, such as rheumatoid arthritis, bacterial infection, tumor, or vasculitis is present. It has an inhibitory function directed against proteolytic enzymes, such as trypsin, elastin, and plasmin, released by alveolar macrophages and bacteria. In the absence of alpha1-AT, functional tissue is destroyed by proteolytic enzymes and replaced with excessive connective tissue.
Decreased levels are found in affected patients with COPD and in children with cirrhosis of the liver. COPD develops at an earlier age in alpha1-AT–deficient patients with COPD than in other patients with COPD. Deficiency of alpha1-AT is the most common cause of liver disease in the pediatric population. Typically, alpha1-AT–deficient patients have circulating levels less than 50 mg/dL (0.5 g/L). Patients who have alpha1-AT values less than 100 mg/dL (1 g/L) should be phenotyped.
Inherited deficiencies are associated early in life with development of lung and liver disorders. Alpha1-AT deficiency is passed on as an autosomal recessive trait. In the pediatric population, the ZZ phenotype usually presents as liver disease, cholestasis, and cirrhosis. Greater than 80% of ZZ-deficient individuals ultimately develop chronic lung or liver disease. It is important to identify inherited deficiencies early in life. alpha1-AT levels may be falsely elevated (i.e., reflect normal values) in patients who are heterozygous alpha1-AT–deficient during concurrent infection, pregnancy, estrogen therapy, steroid therapy, cancer, and postoperative periods. Patients who are homozygous alpha1-AT–deficient do not show such an elevation.
Knowledge of genetics assists the nurse in identifying patients and family members who may benefit from additional education, risk assessment, and counseling. Genetics is the study and identification of genes, genetic mutations, and inheritance. For example, genetics provides some insight into the likelihood of inheriting a medical condition such as a deficiency of alpha1-AT.
Factors That May Alter the Results of the Study
- Drugs and other substances that may increase serum alpha1-AT levels include aminocaproic acid, estrogen therapy, oral contraceptives (high-dose preparations), streptokinase, tamoxifen, and typhoid vaccine
- Rheumatoid factor causes false-positive elevations.
Other Considerations
- Alpha1-AT is an acute-phase reactant protein, and any inflammatory process elevates levels. If a serum C–reactive protein is performed simultaneously and is positive, the patient should be retested for alpha1-AT in 10 to 14 days.
Before the Study: Planning and Implementation
Teaching the Patient What to Expect
- Discuss how this test can assist in identifying lung and liver disease.
- Explain that a blood sample is needed for the test.
After the Study: Implementation & Evaluation Potential Nursing Actions
Avoiding Complications
- Assess for fluid retention that can lead to pulmonary edema.
- Discuss the ramifications of abnormal findings to facilitate protection of the lungs (e.g., avoid contact with persons who have respiratory or other infections; avoid the use of tobacco; avoid areas having highly polluted air; and avoid work environments with hazards such as fumes, dust, and other respiratory pollutants).
- Assess for changes in work of breathing and use of accessory muscles.
Treatment Considerations
- Instruct the patient to resume usual medication as directed by the HCP.
- Monitor respiratory rate and effort based on assessment of patient condition.
- Frequently assess lung sounds and suction secretions as deemed necessary to maintain a clear airway.
- Facilitate use of pulse oximetry to monitor oxygen saturation, and titrate ordered oxygen to patient needs as ordered.
- Elevate the head of the bed 30 degrees to ease breathing and facilitate gas exchange.
- Monitor IV fluids, avoid aggressive fluid resuscitation, and observe for abdominal ascites.
Nutritional Considerations
- Note that malnutrition is commonly seen in alpha1-AT–deficient patients who have severe respiratory disease for many reasons, including fatigue, lack of appetite, and gastrointestinal distress.
- Explain that poor dental health may also be a contributing factor to malnutrition.
- Recognize daily caloric intake required for respiration in patients with COPD is estimated as 10 times higher than that required in healthy individuals.
- Consider how inadequate nutrition can result in hypophosphatemia, especially in respirator-dependent patients. During periods of starvation, phosphorus leaves the intracellular space and moves outside the tissue, resulting in dangerously decreased phosphorus levels.
- Administer multivitamin as prescribed; adequate intake of vitamins A and C is important to prevent pulmonary infection and to decrease the extent of lung tissue damage.
- Stress the importance of following the diet prescribed by the HCP.
- Consider how a dietary consult with assessment of cultural food selections can be helpful toward improving nutrition.
- Monitor water balance closely in alpha1-AT–deficient patients with COPD.
- Consider strategies to improve dietary intake, document food intake, calorie count, assess barriers to eating, consider using a food diary, consume frequent small meals, and complete a daily weight.
- Discourage alcohol use as it is a barrier to adequate nutrition.
- Monitor and trend liver function tests (Alb, ALT, ALP, AST, TBil, TP), glucose, folic acid, thiamine, electrolytes.
- Facilitate parenteral and enteral nutrition as needed.
Clinical Judgement
- Consider which common sense solutions can ease respiratory distress and facilitate improved nutrition. If the patient can’t breath they can’t eat.
Follow-Up and Desired Outcomes
- Acknowledges the importance of smoking cessation to overall health management.
- Understands the necessity to keep scheduled laboratory appointments to monitor liver function and disease progress.
- Maintains specific home oxygen therapy to manage ineffective gas exchange.
- Successfully demonstrates diaphragmatic breathing and pursed-lip breathing to enhance breathing patterns as appropriate.
- Acknowledges that because decreased alpha1-AT can be an inherited disorder, it may be appropriate for the HCP to recommend resources for genetic counseling if levels less than 100 mg/dL (1 g/L) are reported. Patient is aware that alpha1-AT phenotype testing can be performed on family members to determine the homozygous or heterozygous nature of the deficiency.