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Alpha-fetoprotein (AFP)

Definition

Alpha-fetoprotein (AFP)
is a glycoprotein produced by fetal tissue and tumors that differentiate from midline embryonic structures. During fetal development, AFP levels in serum and amniotic fluid rise; because this problem crosses the placenta, it appears in maternal serum. In late stages of pregnancy, AFP levels in fetal and maternal serum and in amniotic fluid begin to diminish. During the first year of life, serum AFP levels continue to decline and usually remain how low thereafter.
High maternal serum AFP levels may suggest fetal tube defects, such as spina bifida and anencephaly; but positive confirmation requires amniocentesis and ultrasongraphy. Other congenital anomalies, such as Down syndrome and other chromosomal disorders, may be associated with low maternal serum AFP concentrations.
Elevated serum AFP levels in 70% of nonpregnant persons may indicate hepatocellular carcinoma (although low AFP levels don’t rule it out) or germ cell tumor of gonadal, retroperitoneal, or mediastinal origin.
Serum AFP level rises in patients with ataxiatelangiectasia and in patients with cancer of the pancreas, stomach, or biliary system. Transient modest elevations can occur in nonneoplastic hepatocellular disease, such as alcoholic cirrhosis and acute or chronic hepatitis. Elevation of AFP levels after remission suggests tumor recurrence.

Purpose
  • To monitor the effectiveness of therapy in malignant conditions, such as hepatomas and germ cell tumors, and certain nonmalignant conditions such as ataxiatelengiectasia.
  • To screen those patients needs amniocentesis or high-resolution ultrasonography during pregnancy.

Procedure
Preparation
  1. Explain that the AFP tests helps in monitoring fetal development, screens for a need for further testing, helps detect possible congenital defects in the fetus, and monitors the patient’s response to therapy by measuring a specific blood protein, as appropriate.
  2. Inform the patient that she need not restrict food, fluids, or medications.
  3. Tell the patient that the test requires a blood sample. Explain who will perform the venipuncture and when.
  4. Explain to the patient that she may experience slight discomfort from the tourniquet and needle puncture.
Implementation
  1. Perform a venipuncture and collect the sample in a 7 ml clot-activator tube.
  2. Record the patient’s age, race, weight, and week of gestation on the laboratory request.
  3. Handle the sample gently to prevent hemolysis.
Nursing Interventions
  1. Place the patient in comfortable position.
  2. Encourage deep breathing exercise to alleviate fear.
  3. Apply direct pressure to the venipuncture site until bleeding stops.

Interpretation
Normal Results
  • When testing by immunoassay, AFP values are less than 15 ng/ml (SI, <15 mg/l) in male patients and nonpregnant female patients.
  • Values in maternal serum normally are less 25 ng/ml (SI, 25 ug/L). At 15 to 18 weeks gestation, values range from 10 to 150 ng/ml (SI, 10 to 150 ug/L).
Abnormal Results
  • Elevated maternal serum AFP level may suggest neural tube defect or other tube anomalies.
  • Definitive diagnosis requires ultrasonography and amniocentesis.
  • High AFP levels may indicate intrauterine death, or high levels indicate other anomalies, such as duodenal atresia, omphalocele, tetralogy of fallot, and Tuner’s syndrome.
  • Elevated serum AFP levels occur in 70% of nonpregnant patients with hepatocellular carcinoma.
  • Elevated levels are also related to germ cell tumor of gonadal, retroperitoneal, or mediastinal origin.
  • Transient modest elevations can occur in nonneoplastic hepatocellular disease, such as alcoholic cirrhosis and acute or chronic hepatitis.
  • Elevation of AFP levels after remission suggests tumor recurrence.

Precautions
  • Handle the sample gently to prevent hemolysis.

Interfering Factors
  • Hemolysis from rough handling of the sample.
  • Multiple pregnancies that may cause false positive result.

Complications
  • Hematoma at the venipuncture site.

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