alpha1-Fetoprotein

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α1-Fetoprotein

Synonym/acronym: AFP.

Common use

To assist in the evaluation of fetal health related to neural tube defects and some forms of liver cancer.

Specimen

Serum (1 mL for tumor marker in men and nonpregnant women; 3 mL for maternal triple- or quad-marker testing), collected in a gold-, red-, or red/gray-top tube. For maternal triple- or quad-marker testing, include human chorionic gonadotropin and free estriol measurement.

Normal findings

(Method: Immunochemiluminometric assay)

α1-Fetoprotein as a Tumor Marker: Males, Females, and Children

Males (Conventional Units)SI Units (Conventional Units × 1)Females (Conventional Units)SI Units (Conventional Units × 1)
Less than 1 mo0.5–16,387 ng/mL0.5–16,387 mcg/L0.5–18,964 ng/mL0.5–18,964 mcg/L
1–11 mo0.5–28.3 ng/mL0.5–28.3 mcg/L0.5–77 ng/mL0.5–77 mcg/L
1–3 yr0.5–7.9 ng/mL0.5–7.9 mcg/L0.5–11.1 ng/mL0.5–11.1 mcg/L
4 yr and olderLess than 6.1 ng/mLLess than 6.1 mcg/LLess than 6.1 ng/mLLess than 6.1 mcg/L
Values may be higher for premature newborns.
α1-Fetoprotein (AFP) in Maternal Serum for Triple or Quad Marker
White AFP (Median)Black AFP (Median)Hispanic AFP (Median)Asian AFP (Median)
Low riskLess than 2 MoMLess than 2 MoMLess than 2 MoMLess than 2 MoM
MoM = multiples of the median. Serum values vary with maternal race, weight, weeks of gestation, diabetic status, and number of fetuses, and variations exist between test methods. Serial testing should be determined using the same test method.
Gestational Age (wk)HCG (Conventional Units)SI Units (Conventional Units × 1)
2 wk5–100 milli-international units/mL5–100 international units/L
3 wk200–3,000 milli-international units/mL200–3,000 international units/L
4 wk10,000–80,000 milli-international units/mL10,000–80,000 international units/L
5–12 wk90,000–500,000 milli-international units/mL90,000–500,000 international units/L
13–24 wk5,000–80,000 milli-international units/mL5,000–80,000 international units/L
26–28 wk3,000–15,000 milli-international units/mL3,000–15,000 international units/L
Pregnancy-associated plasma protein A (PAPP-A)
8 wk90–7,000 milli-international units/L
9 wk0–5,800 milli-international units/L
10 wk140–7,000 milli-international units/L
11 wk575–7,250 milli-international units/L
12 wk900–9,000 milli-international units/L
13 wk550–11,500 milli-international units/L
14 wk2,200–39,500 milli-international units/L
Unconjugated Estriol (E3) (Conventional Units)SI Units (Conventional Units × 3.467)
30 wk3.5–19 ng/mL12.1–65.9 nmol/L
34 wk5.3–18.3 ng/mL18.4–63.5 nmol/L
35 wk5.2–26.4 ng/mL18–91.6 nmol/L
36 wk8.2–28.1 ng/mL28.4–97.5 nmol/L
37 wk8–30.1 ng/mL27.8–104.4 nmol/L
38 wk8.6–38 ng/mL29.8–131.9 nmol/L
39 wk7.2–34.3 ng/mL25–119 nmol/L
40 wk9.6–28.9 ng/mL33.3–100.3 nmol/L
Results vary widely among laboratories and methods.HCG = human chorionic gonadotropin.

Description

Maternal blood screening for birth defects is optimally performed between 16 and 18 wk but may be done as early as 15 wk or as late as 22.9 wk. A number of serum and amniotic fluid markers can be used in collaboration to screen for Down syndrome, neural tube defects, and trisomy 18. These markers include α1-fetoprotein (AFP), human chorionic gonadotropin (HCG), unconjugated estriol, dimeric inhibin-A (DIA), and pregnancy-associated plasma protein A (PAPP-A). Ultrasound (nuchal translucency [NT] ultrasound measurements of the fluid-filled space in the back of the fetus’s neck, larger-than-normal NT measurements are found in Down syndrome), maternal age, race, weight, diabetic status, and number of fetuses are also factors used to calculate risk. The algorithm used to calculate risk depends on whether gestational age is based on ultrasound findings or date of last menstrual period. Diagnostic tests that include AFP, acetylcholinesterase, chromosome analysis, and fetal hemoglobin testing performed on amniotic fluid are discussed in the monographs titles “Amniotic Fluid Analysis” and “Biopsy, Chorionic Villus.”

AFP is a glycoprotein produced in the fetal liver, gastrointestinal tract, and yolk sac. AFP is the major serum protein produced for 10 wk in early fetal life. (See “Amniotic Fluid Analysis” monograph for measurement of AFP levels in amniotic fluid.) After 10 wk of gestation, levels of fetal AFP can be detected in maternal blood, with peak levels occurring at 16 to 18 wk. Elevated maternal levels of AFP on two tests taken 1 wk apart suggest further investigation into fetal well-being by ultrasound or amniocentesis. HCG, a hormone secreted by the placenta, stimulates secretion of progesterone by the corpus luteum. (The use of HCG as a triple marker is also discussed in the monograph titled “Human Chorionic Gonadotropin.”) During intrauterine development, the normal fetus and placenta produce estriol, a portion of which passes into maternal circulation. Decreased estriol levels are an independent indicator of neural tube defects. Dimeric inhibin-A (DIA) is the fourth biochemical marker used in prenatal quad screening. It is a glycoprotein secreted by the placenta. Maternal blood levels of DIA normally remain fairly stable during the 15th to 18th weeks of pregnancy. Blood levels are twice as high in the second trimester of pregnancies affected by Down syndrome. The incidence of Down syndrome is 1 in 750 live births. The triple screen detection rate for Down syndrome is 67%. The Down syndrome detection rate increases to 76% and maintains a false-positive rate of 5% when DIA is included. The incidence of neural tube defects is 1 in 1,300 pregnancies; anencephaly is almost always fatal at, or within a very short time after, birth. The incidence of trisomy 18 is 1 in 4,100 live births; most die within the first year after birth.

The presence of AFP in excessive amounts is abnormal in adults and children. AFP measurements are used as a tumor marker to assist in the diagnosis of cancer.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the diagnosis of primary hepatocellular carcinoma or metastatic lesions involving the liver, as indicated by highly elevated levels (30% to 50% of Americans with liver cancer do not have elevated AFP levels)
  • Investigate suspected hepatitis or cirrhosis, indicated by slightly to moderately elevated levels
  • Monitor response to treatment for hepatic carcinoma, with successful treatment indicated by an immediate decrease in levels
  • Monitor for recurrence of hepatic carcinoma, with elevated levels occurring 1 to 6 mo before the patient becomes symptomatic
  • Investigate suspected intrauterine fetal death, as indicated by elevated levels
  • Routine prenatal screening at 15 to 16 wk of pregnancy for fetal neural tube defects and other disorders, as indicated by elevated levels in maternal serum and amniotic fluid
  • Support diagnosis of embryonal gonadal teratoblastoma, hepatoblastoma, and testicular or ovarian carcinomas

Potential diagnosis

Maternal serum AFP test results report actual values and multiples of the median (MoM) by gestational age (in weeks). MoM are calculated by dividing the patient’s AFP by the midpoint (or median) of values expected for a large population of unaffected women at the same gestational age in weeks. MoM should be corrected for maternal weight. The MoM should also be corrected for maternal insulin requirement (achieved by dividing MoM by 1.1 for diabetic African American patients and by 0.8 for diabetic patients of other races) and multiple fetuses (multiply by 2.13 for twins). Some laboratories also provide additional statistical information regarding Down syndrome risk.

Increased in

  • Pregnant women:
    • Congenital nephrosis (related to defective renal reabsorption)
    • Fetal abdominal wall defects (related to release of AFP from open body wall defect)
    • Fetal distress
    • Fetal neural tube defects (e.g., anencephaly, spina bifida, myelomeningocele) (related to release of AFP from open body wall defect)
    • Low birth weight (related to inaccurate estimation of gestational age)
    • Multiple pregnancy (related to larger quantities from multiple fetuses)
    • Polycystic kidneys (related to defective renal reabsorption)
    • Underestimation of gestational age (related to the expectation of a lower value based on incorrect prediction of gestational age, i.e., AFP increases with age; therefore, if the age is believed to be less than it is actually, the expectation of the corresponding AFP value will be lower than it is actually, and the result appears to be elevated)
  • Men, nonpregnant women, and children (the cancer cells contain undifferentiated hepatocytes that produce glycoproteins of fetal origin):
    • Cirrhosis
    • Hepatic carcinoma
    • Hepatitis
    • Metastatic lesions involving the liver

Decreased in

    Pregnant women:
    • Down syndrome (trisomy 21)
    • Edwards’ syndrome (trisomy 18)
    • Fetal demise (undetected over a lengthy period of time) (related to cessation of AFP production)
    • Hydatidiform moles (partial mole may secrete some AFP)
    • Overestimation of gestational age (related to the expectation of a higher value based on incorrect prediction of gestational age; i.e., AFP increases with age; therefore, if the age is believed to be greater than it actually is, the expectation of the corresponding AFP value will be greater than it actually is, and the result appears to be decreased)
    • Pseudopregnancy (there is no fetus to produce AFP)
    • Spontaneous abortion (there is no fetus to produce AFP)

Critical findings

    N/A

Interfering factors

  • Drugs that may decrease AFP levels in pregnant women include acetaminophen, acetylsalicylic acid, and phenacetin.
  • Multiple fetuses can cause increased levels.
  • Gestational age must be between 15 and 22 wk for initial and follow-up testing. The most common cause of an abnormal MoM is inaccurate estimation of gestational age (defined as weeks from the first day of the last menstrual period).
  • Maternal AFP levels vary by race.

Nursing Implications and Procedure

Potential nursing problems

ProblemSigns & SymptomsInterventions
Fear (Related to prognosis secondary to diagnosis [cancer]; disabled child; ability to function in caregiver role; risk of death (cancer); loss of control; ineffective coping; unfamiliar therapeutic regime; unknown)Expression of fear; preoccupation with fear; increased tension; increased blood pressure; increased heart rate; vomiting; diarrhea; nausea; fatigue; weakness; insomnia; shortness of breath; increased respiratory rate; withdrawal; panic attacksProvide specific education related to disease process (neural tube defect, liver disease); provide specific information related to treatment based on diagnosis or defect; access social services; ensure education is culturally appropriate; assist the patient and family to recognize effective coping strategies; assist the patient and family to acknowledge their fear; provide a safe environment to discuss fear; explore cultural influences that may enhance fear; utilize therapeutic touch as appropriate to decrease fear
Fatigue (Related to hepatic disease process; malnutrition; anemia; chemotherapy; radiation therapy)Decreased concentration; increased physical complaints; inability to restore energy with sleep; report of being tired; inability to maintain normal routineAssess for physical cause of fatigue; pace activities to preserve energy stores; rate fatigue on a numeric scale to trend degree of fatigue over time; identify what aggravates and decreases fatigue; assess for related emotional factors such as depression; evaluate current medications in relation to fatigue; assess for physiologic factors such as anemia
Confusion; altered sensory perception (Related to an alteration in fluid and electrolytes, hepatic disease and encephalopathy; acute alcohol consumption; hepatic metabolic insufficiency)Disorganized thinking, restless, irritable, altered concentration and attention span, changeable mental function over the day, hallucinations; altered attention span; unable to follow directions; disoriented to person, place, time, and purpose; inappropriate affectTreat the medical condition; correlate confusion with the need to reverse altered electrolytes; evaluate medications; prevent falls and injury through appropriate use of postural support, bed alarm, or restraints; consider pharmacological interventions; record accurate intake and output to assess fluid status; monitor blood ammonia level; determine last alcohol use; assess for symptoms of hepatic encephalopathy such as confusion, sleep disturbances, incoherence; protect the patient from physical harm; administer lactulose as prescribed
Spirituality (Related to significant loss; fear of death; debilitation disease process; diagnosed child disability)Forgiveness; acceptance; anger at spiritual leaders; expressed feelings of hopeless, powerlessness; abandonment; refusals or inability to participate in spiritual activities (prayer); expresses feelings over lack of meaning with life or serenity Encourage the verbalization of feelings in a safe, nonjudgmental environment; assess the desire for contact from associated spiritual leader; foster a supportive relationship with the patient and family; encourage a display of objects (spiritual, religious) that provide emotional relief; assess for expressions of hope

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating fetal health.
  • Obtain a history of the patient’s complaints and known or suspected malignancy. Obtain a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s immune and reproductive systems, gestational age, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results.
  • Provide required information to laboratory for triple-marker testing, including maternal birth date, weight, age, race, calculated gestational age, gestational age by ultrasound, gestational date by physical examination, first day of last menstrual period, estimated date of delivery, and whether the patient has insulin-dependent (type 1) diabetes.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.
  • Consent may be required for this type of testing. As appropriate make sure a written and informed consent has been signed prior to the venipuncture procedure.

Intratest

  • Potential complications:
  • N/A

  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • The sample may be collected directly from the cord using a syringe and transferred to a red-top tube.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Nutritional Considerations: Hyperhomocysteinemia resulting from folate deficiency in pregnant women is believed to increase the risk of neural tube defects. Elevated levels of homocysteine are thought to chemically damage the exposed neural tissue of the developing fetus. As appropriate, instruct pregnant patients to eat foods rich in folate, such as liver, salmon, eggs, asparagus, green leafy vegetables, broccoli, sweet potatoes, beans, and whole wheat.
  • Social and Cultural Considerations: In pregnant patients, recognize anxiety related to test results, and encourage the family to seek counseling if concerned with pregnancy termination or to seek genetic counseling if a chromosomal abnormality is determined. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Decisions regarding elective abortion should take place in the presence of both parents. Provide a nonjudgmental, nonthreatening atmosphere for discussing the risks and difficulties of delivering and raising a developmentally challenged infant, as well as exploring other options (termination of pregnancy or adoption). It is also important to discuss feelings the mother and father may experience (e.g., guilt, depression, anger) if fetal abnormalities are detected. Educate the patient regarding access to counseling services.
  • In patients with carcinoma, recognize anxiety related to test results, and offer support. Discuss the implications of abnormal test results on the patient’s lifestyle.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Inform the pregnant patient that an ultrasound may be performed and AFP levels in amniotic fluid may be analyzed if maternal blood levels are elevated in two samples obtained 1 wk apart. Evaluate test results in relation to the patient’s symptoms and other tests performed.
  • Patient Education

    • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
    • Answer any questions or address any concerns voiced by the patient or family.
    • Provide teaching and information regarding the clinical implications of the test results, as appropriate.
    • Educate the patient regarding access to counseling services, as appropriate.
  • Expected Patient Outcomes

    • Knowledge
    • States understanding that neural tube defect is a causative factor in birth disabilities
    • States a clear understanding of the plan of care developed to support the health of the disabled child
    • Skills
    • Designs a plan to support the home care of the disabled child while meeting own basic needs
    • Demonstrates proficiency in administering medication to the disabled child
    • Attitude
    • Complies with the request to attend a support group for parents of disabled children
    • Complies with the recommendation to abstain from alcohol use as it can exacerbate liver disease

Related Monographs

  • Related tests include amniotic fluid analysis and L/S ratio, biopsy chorionic villus, cancer antigens, estradiol, fetal fibronectin, folic acid, hexosaminidase, homocysteine, HCG, L/S ratio, and US biophysical profile obstetric.
  • Refer to the Immune and Reproductive systems tables at the end of the book for related tests by body system.
References in periodicals archive ?
HAS was identified as an adenocarcinoma exhibiting solid/trabecular, pseudoglandular growth pattern with large polygonal eosinophilic cells and staining positively with polyclonal rabbit anti-human a1-fetoprotein and monoclonal mouse anti-human hepatocyte (DAKO, Glostrup, Denmark).