Cytomegalovirus (CMV) is a virus in the herpes family. Other types of herpes viruses include chickenpox and mononucleosis (mono). CMV infections are very common. In the United States, over half of adults have been exposed to CMV at some point in their lives, often during childhood or early adulthood. After initial infection, the virus remains in the body for the rest of your life. Most of the time, the virus stays dormant (inactive). However, it can become active again (reactivated) in certain situations such as stress or an immune system problem.
In healthy people, CMV infections usually cause mild, flu-like illnesses or no symptoms at all. Most people with CMV don’t even know they have it. But CMV can be dangerous to people with weakened immune systems due to conditions such as HIV or cancer. It can also cause significant health problems in infants. A pregnant woman with an active CMV infection can pass the virus to her unborn baby. CMV can cause deafness, vision problems, intellectual disabilities, and other serious disorders in babies who are infected before birth.
CMV tests check for signs of the virus in the blood, sputum, or other body fluids. CMV testing can help those at risk for complications get the treatment they need. While there is no cure for CMV, antiviral medicines and other treatments may reduce symptoms and improve outcomes.
Other names: CMV IgG and IgM, cytomegalovirus antibody
What are they used for?
CMV tests are used to help diagnose a current, reactivated, or past CMV infection in people at risk for health complications. Risk groups include:
- People with weakened immune systems due to certain infections or diseases
- People who have recently received an organ transplant
- Pregnant women with symptoms of a CMV infection
- Newborns with symptoms of infection
Why do I need a CMV test?
You may need testing if you have a weakened immune system or are pregnant and have the following symptoms:
Your baby may need this test if he or she has the following symptoms:
- Jaundice, a condition that causes the skin and eyes to turn yellow
- Low birth weight
- Small head
- Hearing and/or vision problems
What happens during a CMV test?
There are several types of CMV tests, including:
- This is the most common way to test adults for CMV.
- During the test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial.
- A sample of cerebrospinal fluid (CSF) will be collected through a procedure called a spinal tap, also known as a lumbar puncture.
- During the test, a provider will inject a numbing medicine (anesthetic) into your back and insert a thin, hollow needle between two vertebrae in your lower spine. Vertebrae are the small bones that make up your spine.
- Your provider will then withdraw a small amount of fluid for testing.
- Sputum is a thick mucus that settles in your lungs when you have an infection or chronic illness.
- During the test, your health care provider will ask you to breathe deeply and then cough deeply into a special cup.
- Your provider may tap you on the chest to help loosen sputum from your lungs.
- During the test, your provider will remove a small sample of tissue for testing.
- Biopsies can be done with a needle or a special type of surgical instrument.
- This procedure is done on pregnant women to see if an unborn baby has been infected with CMV.
- During the procedure, you’ll lie on your back on an exam table.
- Your provider will move an ultrasound device over your abdomen. Ultrasound uses sound waves to check the position of your uterus, placenta, and baby.
- Your provider will insert a thin needle into your abdomen and withdraw a small amount of amniotic fluid.
Newborns are usually given a saliva or urine test.
During an infant saliva test:
- A provider will insert a sterile swab into your baby’s cheek and swirl for several seconds.
- The swab will be placed in a special solution for testing.
During an infant urine test:
- You will be given a special plastic bag that will fit over your baby’s genital area.
- You will place a diaper over the bag.
- After your baby has urinated, you will remove the bag from the diaper and empty the urine into a container given to you by your provider.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for a blood or sputum test. There are also no preparations needed for an infant saliva or urine test.
You may need to empty your bladder before a lumbar puncture.
You may be asked to fast (not eat or drink) for several hours before a biopsy.
For an amniocentesis, you may be asked to keep a full bladder or empty your bladder right before the procedure, depending on your stage of pregnancy.
Your provider or your child’s provider will let you know if you need to make any other preparations.
Are there any risks to the test?
There are no known risks to having a sputum test, infant saliva test, or infant urine test.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
If you had a lumbar puncture, you may have pain or tenderness in your back when the needle is inserted. You may also get a headache after the procedure. The headache can last for several hours or up to a week or more.
If you had a biopsy, you may have a little bruising, bleeding, or soreness at the biopsy site. This usually goes away after a few days.
If you had an amniocentesis, you may have some mild discomfort and/or cramping during and/or after the procedure, but serious complications are rare. The procedure does have a slight risk (less than 1 percent) of causing a miscarriage.
What do the results mean?
The test result can show whether you have been infected with CMV. But it can’t show if it’s a current, past, or reactivated infection. If you have symptoms and/or risk factors such as an immune system disorder, your provider may do additional tests to help make a diagnosis and create a treatment plan. If you are pregnant and your amniocentesis shows your baby has CMV, your child’s provider may test and treat your baby soon after birth to help prevent complications.
If you have questions about your results, talk to your health care provider or your child’s provider.
Is there anything else I need to know about CMV testing?
CMV tests are included as part of a TORCH panel, a group of blood tests used to screen newborns and sometimes pregnant woman for the following infections:
These infections can cause birth defects if a mother gets infected during pregnancy. Early diagnosis and treatment may help prevent a baby from getting a serious health problem.
Courtesy of MedlinePlus from the National Library of Medicine.