• Normal prolactin test results:
• Pregnant: 20 to 400 ng/mL
• Non-Pregnant: less than 25 ng/mL
• Men: less than 20 ng/mL
High prolactin levels may indicate prolactinoma, idiopathic hyperprolactinemia, hypothyroidism, cirrhosis, or kidney disease.
10.8 Phenylketonuria (PKU) Test
The phenylketonuria (PKU) test measures the level of the phenylalanine hydroxylase enzyme in blood. Pheny- lalanineis an amino acid in breast milk, formula, dairy products, and meats. The body requires the phenylala- nine hydroxylase enzyme to metabolize phenylalanine into tyrosine. Phenylketonuria(PKU) is a genetic disorder in which the patient is missing the phenylalanine hydroxylase enzyme and is therefore unable to metabolize phenylalanine, causing a buildup of phenylalanine level in the blood, which results in mental retardation and seizures. Newborns are administered the phenylketonuria (PKU) test between 12 hours and 28 hours after birth, and again a week after birth. Infants older than six weeks of age may be administered a phenylketonuria urine test if a phenylketonuria was not performed at birth. Newborns that are ill are retested three weeks after birth.
Why the Test Is Performed
The test assesses for phenylketonuria.Before Administering the Test
Assess if the:• Newborn ingested formula or breast milk for 48 hours prior to the test
• Newborn was born prematurely
• Patient has vomited prior to the test
• Patient is taking antibiotics
How the Test Is Performed
The newborn should ingest formula or breast milk for 48 hours prior to the test.
Heel Stick: Several drops of blood are collected from the heel of a newborn or baby. The heel is cleaned using alcohol. A sterile lancet is used to puncture the heel. Several drops of blood are collected in a small test tube.
A gauze pad is pressed over the site until bleeding stops. A small bandage is applied.
The healthcare provider may order a blood sample taken from a vein to confirm a positive phenylketonuria test that used a sample from a heel stick.
Teach the Patient
Explain why the sample is taken and that the test may be repeated a week after birth. Inform the parents that the newborn must ingest formula or breast milk for 48 hours prior to the test.
Understanding the Test Results
The phenylketonuria test results are available quickly. Normal phenylketonuria test results are less than 3 mg/dL.
High phenylketonuria test results may indicate phenylketonuria.
10.9 Tay-Sachs Test
The Tay-Sachs test measures the amount of hexosaminidase A in the blood. Hexosaminidase Ais an enzyme that metabolizes ganglioside, which is a fatty acid. If the hexosaminidase A is not present, ganglioside accumulates in brain and nerve cells, resulting in neural damage. This is referred to as Tay-Sachs disease,
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which is an inherited disease. A positive result will be confirmed by genetic testing. The healthcare provider may order an amniocentesis or the chorionic villus sampling of the placenta to determine if the fetus has the hexosaminidase A enzyme.
Why the Test Is Performed
The test assesses for Tay-Sachs disease and if the patient is carrying the Tay-Sachs trait.
Before Administering the Test
Assess if the patient:• Has had a blood transfusion 90 days prior to the test
• Is taking birth control pills
• Is pregnant
How the Test Is Performed
A sample of blood is taken from the patient’s vein. The patient will experience a tight feeling when the tourni- quet is tightened, a pinch or nothing at all when the needle is inserted into the vein, and pressure when a gauze pad is pressed against the insertion site to stop bleeding. It can take up to 10 minutes for bleeding to stop if the patient is taking anticoagulants (aspirin, coumadin). A small bruise might appear at the insertion site, which could become swollen following this test. This is called phlebitis. Applying a warm compress several times a day will reduce the swelling.
Teach the Patient
Explain why the sample is taken, that the test result may indicate that the patient carries the Tay-Sachs trait and recommend genetic counseling, and that the healthcare provider may ask the patient to refrain from taking birth control pills prior to the test.
Understanding the Test Results
The Tay-Sachs test results are available quickly. The laboratory determines normal values based on calibration of testing equipment with a control test. Test results are reported as high, normal, or low based on the labora- tory’s control test.
• Normal test results:
• Total hexosaminidase: 10.4 to 23.8 U/L
• Percentage of blood level: 56% to 80%
A half-normal level may indicate that the patient is a carrier of the Tay-Sachs trait.
No hexosaminidase A enzyme may indicate Tay-Sachs disease or Sandhoff’s disease (missing hex- osaminidase A and hexosaminidase B).
10.10 Sickle Cell Test
The sickle cell test determines if the patient has sickled blood cells, which is an abnormal form of hemoglobin.
Normal red blood cells contain hemoglobin A. In sickle cell disease, red blood cells contain hemoglobin S, which causes the red blood cell to form a sickle shape and is therefore called a sickled blood cell. Sickle cell dis- ease is an autosomal recessive disease where the sickle cell gene must be inherited from both parents. Patients with sickled blood cells can experience a sickle cell crisis when sickled blood cells block blood vessels, result- ing in decreased blood flow. Sickled blood cells are destroyed faster than normal red blood cells, leading to sickle cell anemia. The patient should undergo genetic counseling if the patient has the sickle cell trait or sickle cell disease. The healthcare provider may order the HPLC test to examine the patient’s DNA for the sickle cell gene. Sickle cell disease is more prevalent in African Americans. Healthcare providers commonly test newborns CHAPTER 10 Pregnancy and Genetic Tests 115
for the sickle cell trait although infants under 6 months old can have false-negative test results, since they have fetal hemoglobin in their blood, and therefore the sickle cell test is repeated after 6 months of age. The health- care provider may order the sickle cell test for a fetus using chorionic villus sampling (CVS) or amniocentesis.
Why the Test Is Performed
The test assesses for the sickle cell trait and sickle cell disease.
Before Administering the Test
• Assess if the patient has received a blood transfusion within three months before the test is administered.
• The patient should undergo genetic counseling if the test is positive for sickle cell trait or sickle cell disease.
How the Test Is Performed
A sample of blood is taken from the patient’s vein. The patient will experience a tight feeling when the tourni- quet is tightened, a pinch or nothing at all when the needle is inserted into the vein, and pressure when a gauze pad is pressed against the insertion site to stop bleeding. It can take up to 10 minutes for bleeding to stop if the patient is taking anticoagulants (aspirin, coumadin). A small bruise might appear at the insertion site, which could become swollen following this test. This is called phlebitis. Applying a warm compress several times a day will reduce the swelling.
Teach the Patient
Explain why the sample is taken and that the patient should receive genetic counseling if the sickle cell trait or sickle cell disease is present.
Understanding the Test Results
The sickle cell test result is available quickly. A normal sickle cell test result is normal hemoglobin presence.
An abnormal sickle cell test result is some presence of Hemoglobin S.
• Sickle cell trait: 35%–45% of red blood cells have Hemoglobin S.
• Sickle cell disease: Nearly all red blood cells have Hemoglobin S.
10.11 Hemochromatosis Gene Test (HFE)
The hemochromatosis gene test (HFE) determines if the patient has the hemochromatosis gene. The hemochromato- sis gene increases the absorption of iron (hemochromatosis), which causes a buildup of iron in the liver, heart, blood, joints, skin, and pancreas, resulting in joint pain, weight loss, and decreased energy. This can lead to arrhythmia, cir- rhosis, diabetes, heart failure, arthritis, and change in skin color. Existence of the hemochromatosis gene means that the patient has an increased chance of having hemochromatosis, but does not mean that the patient has hemochro- matosis. The hemochromatosis gene test may not rule out the existence of the hemochromatosis gene. The test detects the most common hemochromatosis gene mutation, but not all mutations. It is advised that the patient con- sult a genetic counselor before the test is administered to discuss the risks of developing hemochromatosis. The healthcare provider will order the test if close family members have hemochromatosis. The healthcare provider might order the ferritin level test and transferrin saturation test to measure the level of iron in the patient’s blood.
Why the Test Is Performed
The test screens for the presence of the hemochromatosis gene. The test assesses the underlying cause of hemo- cromatosis. If positive, other tests for hemocromatosis are not necessary. The test also assesses the treatment for hemocromatosis.
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Before Administering the Test
Assess if the patient has:• Received a blood transfusion within a week before the test is administered
• Undergone genetic counseling prior to the test
How the Test Is Performed
A sample of blood is taken from the patient’s vein. The patient will experience a tight feeling when the tourni- quet is tightened, a pinch or nothing at all when the needle is inserted into the vein, and pressure when a gauze pad is pressed against the insertion site to stop bleeding. It can take up to 10 minutes for bleeding to stop if the patient is taking anticoagulants (aspirin, coumadin). A small bruise might appear at the insertion site, which could become swollen following this test. This is called phlebitis. Applying a warm compress several times a day will reduce the swelling.
Teach the Patient
Explain why the sample is taken, that the patient should receive genetic counseling prior to the test, and that a positive test result does not mean that the patient will develop hemochromatosis. It means that the patient is at risk for developing hemochromatosis.
Understanding the Test Results
The hemochromatosis gene test result is available in 2 weeks.
• A normal hemochromatosis gene test result is (negative): No mutation found.
• An abnormal hemochromatosis gene test result is (positive): Mutation found. The patient has a risk of developing hemochromatosis.
Solved Problems
Antisperm Antibody Test
10.1 Why is the antisperm antibody test administered?
The antisperm antibody test is administered to assess if antisperm antibodies are in blood, vaginal fluid, or semen, and to assess if infertility may be caused by immunologic infertility.
10.2 What should you be concerned about before administering the antisperm antibody test?
Patients may be embarrassed about collecting a sample. Confer with the healthcare provider if masturbation is against the patient’s religious beliefs.
10.3 How is a semen sample collected?
A semen sample is collected by masturbation. Urinate. Wash and rinse your hands and penis. Collect the semen in a sterile cup. Do not use lubricants or condoms. Take the sample to the lab within 30 minutes.
10.4 What should you explain to the patient before administering the antisperm antibody test?
Explain why the test is ordered, that the patient should not ejaculate for 2 days before the test and no longer than 5 days before the test; how to collect the semen sample; that the patient should take the sample to the lab within 30 minutes; and that the patient should not use lubricants or condoms when collecting the sample. Ask the patient to consult his healthcare provider if masturbation is against the patient’s religious beliefs.
10.5 What does a positive antisperm antibody test result mean?
Positive test results mean that antisperm antibodies are found.