Varicella – Zoster( Chckenpox ) Antibody

Tests for chicken pox and shingles are done to diagnose either a current or past infection with the virus (VZV) that causes these conditions. Formal tests are often unnecessary when there is an active infection, because a diagnosis can be made by the doctor just from examining the clinical signs and symptoms, but a diagnostic test helps to confirm the infection in patients with unusual or severe symptoms,. In people who are at higher risk from VZV infection, (such as organ transplant recipients or pregnant women), tests for VZV antibody may be useful to determine whether a person is immune.

Background
Varicella zoster virus is a member of the herpes virus family. It is very common and the primary infection (chickenpox) is highly contagious, passing from person to person directly from the blisters, or through exhaled droplets and coughs. VZV causes chickenpox in children and adults who have not been previously exposed. Usually, about two weeks after exposure to the virus, an itchy rash occurs, followed by the pimple-like spots that become small, fluid-filled blisters (vesicles). The blisters break, form a crust and then heal. Typically, this process occurs in two or three waves or “crops” of several hundred blisters over a few days.

Once the first infection has got better, the virus becomes hidden (latent) in sensory nerve cells near the spinal cord. The person develops antibodies during the infection that usually prevent them from getting chickenpox again if exposed to the virus. However, later in life and in those with immune systems that are not working properly, VZV can reactivate, moving down the nerve cells to the skin and causing shingles (also known as herpes zoster). Symptoms of shingles include a mild to intense burning or itching pain occurring in a band of skin. It is usually limited to one place on one side of the body, often on the trunk or the face, but can also occur in several places. Several days after the pain, itching, or tingling begins, a rash forms in the same place. The rash may, or may not, develop into blisters. People with active shingles can spread VZV infection to others who have never had the infection, causing chickenpox. In most people, the rash and pain of shingles reduces within a few weeks and the virus again becomes hidden (latent). A few people may have pain that lingers for several months (known as post-herpetic neuralgia).

Most cases of chickenpox and shingles get better without complications. Occasionally the broken blisters can become infected with bacteria. Rarely, the virus can spread to the lungs or the brain, to cause life-threatening infection. In people with compromised immune systems, or who are pregnant, VZV infections can be more severe and long-lasting.

The possible effects of VZV on a growing baby or newborn depend on when exposure occurs and on whether or not the mother has been previously infected. During the first 20 weeks of pregnancy, a primary VZV infection in the mother may, rarely, cause congenital abnormalities in her growing baby. Babies infected in utero are also more likely to develop shingles in infancy. If the mother’s infection occurs one to three weeks before delivery, the baby may develop chickenpox just before or after birth, although antibodies passed from the mother may start to give some protection. If a newborn is exposed to VZV near to birth and does not have maternal antibody protection, then the VZV infection can be severe or even fatal.

How is the sample collected for testing?

The sample required depends on the patient’s symptoms (if any) and whether testing is being done to determine the presence of antibodies or to detect the DNA of the virus itself. Antibody testing requires a blood sample collected from a vein in the arm. Varicella zoster virus DNA may be detected from a variety of samples, including a swab from the rash or throat, blood and cerebrospinal fluid.

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

No test preparation is needed.