The CMV serology test determines the presence of antibodies to cytomegalovirus (CMV) in the blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

Serology studies the fluid portion of blood (serum) for its antibody content. Serology tests are often repeated a few weeks after the first sample. There are several serology techniques that can be used, depending on the suspected antibodies.

There is no special preparation for the test.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

The test is performed to detect current active CMV infection, or past CMV infection in people who are at risk for reactivation of infection (such as organ transplant recipients and people with a suppressed immune system). The test may also be performed to detect CMV infection in newborns.

People who have never been infected with CMV have no detectable antibodies to CMV.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The presence of positive antibodies to CMV indicates a current or prior infection with CMV. If the number of antibodies rises over a few weeks, it may mean that you have an acute infection.

Chronic CMV infection (where the antibody count stays about the same over time) can become reactivated in a person with a suppressed immune system.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

To detect organ system infection with CMV, the health care provider can get cultures of the specific organ.