Chickenpox screening

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Michael Maddaleni, B.S.

Overview

• Screening aids in early diagnosis and treatment. Screening tests are recommended for people without current symptoms, but for those at high risk for certain diseases or conditions.
• Here, screening is done to determine whether if the person has acquired an immunity to the disease.
• Blood tests are done to measure the levels of antibodies in the blood which indicates whether the individual has developed an immunity to chickenpox from previous infection or a missed immunisation.

Screening

• Laboratory tests can help confirm the diagnosis, if needed.

Antibody Testing

• When an individual is exposed to VZV, their immune system responds by producing antibodies to the virus. Laboratory tests detect and measure the level of two classes of VZV antibodies in the blood namely IgM and IgG.

IgM

• First antibodies to be produced in response to the infection.
• Can be detected within a week or two post exposure.
• The levels of IgM antibodies rises for a short period of time and then falls below detectable levels.
• Post-Infection, in the future, the IgM levels rise only when the latent VZV is reactivated.

IgG

• Produced several weeks after the initial exposure.
• IgG levels rise during active infection and then the levels become stable as the VZV infection gets resolves and as the virus gets inactivated.
• Provides Long-Term protection

Viral detection

• Viral detection is done by finding VZV in a blood, vesicle fluid, or tissue sample. Detection done by culturing the virus or by detecting it's genetic material (VZV DNA).

VZV DNA testing

• Performed to detect VZV genetic material in a person's sample. This method is sensitive. It can identify and measure the amount of the virus.

Direct Fluorescent Antibody (DFA) – this test visualizes the presence of VZV in the cells taken from a person's skin lesion using a special microscope and labeled antibody. It is rapid, but less specific and sensitive than DNA testing.

VZV culture

• Culture is not very reliable for VZV and can lead to false-negative results.

The choice of tests and samples collected depends on the person, their symptoms, and on the healthcare practitioner's clinical findings.

References

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