CMV

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Formal name: Cytomegalovirus

At a Glance

Why Get Tested?

If your doctor suspects you presently have, or recently had, a cytomegalovirus (CMV) infection or if it is important to know if you have ever had a CMV infection – such as prior to receiving an organ transplant

When to Get Tested?

When a young adult, a pregnant female, or an immune-compromised patient has typical symptoms that suggest a CMV infection (tiredness, fever, jaundice); when a newborn has multiple congenital anomalies, unexplained jaundice or anaemia, and/or when an infant has seizures or developmental problems that may be due to CMV

Sample Required?

A blood sample taken from a vein in your arm for CMV antibody testing; to detect the virus itself, sample may be blood, urine, or sputum, amniotic fluid, cerebrospinal fluid (CSF), duodenal fluid, or other body tissue

Test Preparation Needed?

No test preparation is needed.

The Test Sample

What is being tested?

Cytomegalovirus (CMV) testing is requested to determine whether someone is currently, or has recently been, infected with CMV. It may also sometimes be used to determine whether someone has ever been exposed to CMV. Testing for CMV involves either a measurement of CMV antibodies (immune proteins created in response to CMV exposure) or by the detection of the virus itself. The virus is detected during an active infection by detecting the genetic material of the virus (its DNA).

In the United Kingdom, as many as 50% to 85% of adults have been infected with CMV. Most people are infected as children or young adults and do not experience any significant symptoms or health problems, but the most common symptoms are fever, tiredness and jaundice. CMV is found in many body fluids during an active infection, including saliva, urine, blood, breast milk, semen, cervical secretions, and cerebrospinal fluid. It is easily transmitted to others through sexual contact and sharing saliva or by contact with infected objects, such as nappies or toys. After the initial “primary” infection has resolved, CMV becomes dormant or latent - like other members of the herpes family. Cytomegalovirus remains in a patient for the rest of their life without causing any symptoms, unless the virus reactivates when a patient’s immune system is compromised.

CMV can cause problems in three areas:

  • In young adults, the initial primary CMV infection may cause an illness characterised by fever, tiredness or jaundice; it usually resolves within a few weeks but can cause prolonged illness with fever and sweating.
  • In infants, primary CMV infection may cause serious physical and developmental problems when women are first infected during pregnancy and then pass the infection to infants across the placental barrier. Most foetuses (about 90%) that are infected appear perfectly normal at birth but may develop hearing or vision problems, pneumonia, seizures, and/or delayed mental development a few months later. A few babies may be stillborn, while others may have symptoms at birth such as jaundice, anaemia, an enlarged spleen or liver, and a small head. Some of these signs and symptoms will resolve with time, but others may persist.
  • In those with compromised immune systems, CMV may cause serious illness and death. This includes those with HIV/AIDS, those who have had organ or bone marrow transplants, and those undergoing chemotherapy treatment for cancer. Patients with compromised immune systems who become infected for the first time may experience more severe symptoms, and the CMV infection may remain active. Those who have been exposed to CMV previously may reactivate their infection. This may affect their eyes (causing inflammation of the retina, which can lead to blindness), gastrointestinal tract (causing bloody diarrhoea and abdominal pain), lungs (causing pneumonia with a non-productive cough and shortness of breath), and brain (causing encephalitis). There can also be spleen and liver involvement, and those who have had organ or bone marrow transplants may experience some degree of rejection. Active CMV also further depresses the immune system, allowing other secondary infections, such as fungal infections, to occur.

How is the sample collected for testing?

The sample required depends on whether testing is being done to determine the presence of antibody or to detect the virus itself and on the health status of the patient. Antibody testing requires a blood sample, obtained by inserting a needle into a vein in the arm. Viral detection may be done on a variety of samples, including urine, blood, or sputum. Some samples may require a special procedure to collect amniotic fluid, duodenal fluid, cerebrospinal fluid, or body tissue (biopsy).

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.