Duchenne/Becker muscular dystrophy DNA detection
What is this test?
This test evaluates the gene mutations and dystrophin (skeletal muscle protein) abnormalities in blood or a muscle tissue sample. It is used to identify patients with suspected Duchenne or Becker muscular dystrophy (D/BMD). It is also used to identify women suspected to be carriers of the D/BMD gene.
What are other names for this test?
- Duchenne muscular dystrophy carrier detection
- Genetic detection of Duchenne/Becker muscular dystrophy
What are related tests?
Why do I need this test?
Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. The following is a possible reason why this test may be done:
- X-linked muscular dystrophy with abnormal dystrophin
When and how often should I have this test?
When and how often laboratory tests are done may depend on many factors. The timing of laboratory tests may rely on the results or completion of other tests, procedures, or treatments. Lab tests may be performed immediately in an emergency, or tests may be delayed as a condition is treated or monitored. A test may be suggested or become necessary when certain signs or symptoms appear.
Due to changes in the way your body naturally functions through the course of a day, lab tests may need to be performed at a certain time of day. If you have prepared for a test by changing your food or fluid intake, lab tests may be timed in accordance with those changes. Timing of tests may be based on increased and decreased levels of medications, drugs or other substances in the body.
The age or gender of the person being tested may affect when and how often a lab test is required. Chronic or progressive conditions may need ongoing monitoring through the use of lab tests. Conditions that worsen and improve may also need frequent monitoring. Certain tests may be repeated to obtain a series of results, or tests may need to be repeated to confirm or disprove results. Timing and frequency of lab tests may vary if they are performed for professional or legal reasons.
How should I get ready for the test?
Before having blood collected, tell the person drawing your blood if you are allergic to latex. Tell the healthcare worker if you have a medical condition or are using a medication or supplement that causes excessive bleeding. Also tell the healthcare worker if you have felt nauseated, lightheaded, or have fainted while having blood drawn in the past.
A muscle biopsy is a procedure that requires your written consent. Review the consent form with the healthcare worker and ask any questions that you have before signing the consent form. You may need to have other tests done before having a muscle biopsy.
Tell the healthcare worker if you have a medical condition or are using a medication or supplement that causes excessive bleeding. Report any past or present muscle diseases or conditions, and if any of your muscles have had previous medical treatments. Tell the healthcare worker if you have a history of allergic or other reactions to local anesthetics.
How is the test done?
A sample of venous blood or muscle tissue may be collected for this test.
When a blood sample from a vein is needed, a vein in your arm is usually selected. A tourniquet (large rubber strap) may be secured above the vein. The skin over the vein will be cleaned, and a needle will be inserted. You will be asked to hold very still while your blood is collected. Blood will be collected into one or more tubes, and the tourniquet will be removed. When enough blood has been collected, the healthcare worker will take the needle out.
One or more muscles will be selected for a muscle tissue biopsy. The vastus lateralis (a muscle of the upper leg) is the muscle most often selected for biopsy. However, the reasons for choosing certain muscles or areas on the muscle vary widely. Muscle selection depends on the type of test, disease suspected, and many other factors. There are several different ways that a biopsy may be performed. A needle biopsy is used to obtain a small sample of muscle tissue. An open biopsy is used to collect a larger muscle sample.
An open biopsy is a surgical procedure. A regional block or general anesthetic may be used for sedation during this procedure. After you are sedated, the biopsy area will be cleaned and prepared for the procedure. During an open biopsy, an incision will be made over or near the muscle to be biopsied. The muscle tissue sample will be collected, and the incision closed.
Before a needle biopsy, local anesthetic will be injected in the procedure area. This medication makes the area numb. A needle will be advanced through the skin and fat layers, and into the muscle. The muscle may be squeezed toward the needle. The needle may be moved in and out, and then removed with the muscle tissue sample.
During the procedure, one or more incisions may be made, and multiple sections of tissue removed. Over time, you may need to have more muscle tissue samples taken. Muscle samples may also be taken on infants before or after they are born.
How will the test feel?
The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.
During a blood draw, you may feel mild discomfort at the location where the blood sample is being collected.
Before a needle biopsy into a muscle, local anesthetic is given to the procedure site to numb the area. You may feel mild discomfort or stinging when the numbing medicine is injected. You may still be able to feel pressure or discomfort. For an open muscle biopsy, an anesthesiologist will give you a general or regional anesthetic. During general anesthesia you receive medicine that puts you into a deep sleep where you are unable to feel pain. With regional anesthesia or a block, you receive medicine that numbs a nerve or group of nerves that supply a certain area of your body. With a regional anesthetic, you are awake but will not feel pain or pressure in the numbed area. For a muscle biopsy, you may experience discomfort in the area for several days.
What should I do after the test?
After a blood sample is collected from your vein, a bandage, cotton ball, or gauze may be placed on the area where the needle was inserted. You may be asked to apply pressure to the area. Avoid strenuous exercise immediately after your blood draw. Contact your healthcare worker if you feel pain or see redness, swelling, or discharge from the puncture site.
After a muscle tissue biopsy, bandages and/or sterile tape may be secured over the incision. Follow the instructions given to you by the healthcare worker regarding changing bandages and caring for the wound or wounds. The biopsy site may be painful for about a week after the procedure. Contact healthcare workers if you see increasing redness, swelling or pus at the procedure site, or for increased pain or new loss of feeling (numbness) in an area.
What are the risks?
Blood: During a blood draw, a hematoma (blood-filled bump under the skin) or slight bleeding from the puncture site may occur. After a blood draw, a bruise or infection may occur at the puncture site. The person doing this test may need to perform it more than once. Talk to your healthcare worker if you have any concerns about the risks of this test.
Muscle tissue: A sample of muscle tissue may be collected by biopsy. Risks of a muscle tissue biopsy include bleeding, bruising, and infection at the procedure site. A subfascial hematoma (a pocket of blood that forms beneath the fatty layer of the skin next to the muscle) may occur. If you have a medical condition, or are using a medication or supplement that causes excessive bleeding, you are at a higher risk of bleeding from the procedure site. Less common risks include muscle contracture (shortening of the muscle) and nerve damage leading to loss of feeling at or around the procedure site.
Depending on the site selected for the muscle biopsy and the method used, other complications are possible. An open biopsy may require sedation (putting you to sleep), which has its own risks. The person doing this procedure may need to perform it more than once. Talk to your healthcare worker if you have any concerns about the risks of having a muscle biopsy.
What are normal results for this test?
Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a disease. Contact your healthcare worker if you have any questions. The following is considered to be a normal result for this test:
- Negative for gene mutation or dystrophin abnormality 
What follow up should I do after this test?
Ask your healthcare worker how you will be informed of the test results. You may be asked to call for results, schedule an appointment to discuss results, or notified of results by mail. Follow up care varies depending on many factors related to your test. Sometimes there is no follow up after you have been notified of test results. At other times follow up may be suggested or necessary. Some examples of follow up care include changes to medication or treatment plans, referral to a specialist, more or less frequent monitoring, and additional tests or procedures. Talk with your healthcare worker about any concerns or questions you have regarding follow up care or instructions.
You may be instructed to rest following a muscle tissue biopsy. Instructions for recovery from a muscle biopsy vary depending on the location where the sample was taken, the procedure used, and other reasons. Ask the healthcare worker for recovery instructions after your procedure. If you had an open biopsy, scarring may occur at the biopsy site.
Where can I get more information?
- Beggs AH & Kunkel LM: Improved diagnosis of Duchenne/Becker muscular dystrophy. J Clin Invest 1990; 85(3):613-619.
- Cox GF & Kunkel LM: Dystrophies and heart disease. Curr Opin Cardiol 1997; 12:329-343.
- Fassati A, Tedeschi S, Bordoni A, et al: Rapid direct diagnosis of deletions carriers of Duchenne and Becker muscular dystrophies. Lancet 1994; 344(8918):302-303.
- Kunkel LM & Hoffman EP: Duchenne/Becker muscular dystrophy: a short overview of the gene, the protein, and current diagnostics. Br Med Bull 1989; 45(3):630-643.
- Cole CG, Walker A, Coyne A, et al: Prenatal testing for Duchenne and Becker muscular dystrophy. Lancet 1988; 1(8580):262-266.