Chickenpox laboratory findings
Chickenpox laboratory findings On the Web
American Roentgen Ray Society Images of Chickenpox laboratory findings
The laboratory findings of chickenpox include blood tests that can be done to identify the response to acute infection (IgM) or previous infection and subsequent immunity (IgG). Prenatal diagnosis of fetal varicella infection can be performed using ultrasound at 5 weeks following primary maternal infection. A PCR test of the mother's amniotic fluid can also be performed, though the risk of spontaneous abortion due to the amniocentesis procedure is higher than the risk of the baby developing fetal varicella syndrome.
Laboratory tests that are shown to be useful for the diagnosis of chickenpox include:
- PCR is done by collecting skin vesicles fluid, scabs, saliva and cerebrospinal fluid if neurological symptoms or signs are present.
- PCR done with a restriction enzyme can be used to hydrolyze and sequence specific segments of the viral genome. This can be used to determine whether VZV is resistant to acyclovir.
- Antibody Testing
- Viral detection
- VZV DNA testing
- Direct Fluorescent Antibody (DFA)
- VZV culture
- Laboratory tests detect and measure the level of VZV antibodies. The presence of IgM antibodies indicates acute infection.
- It can be detected within 1-2 weeks post exposure.
- The levels of IgM antibodies rise for a short period of time and then fall below detectable levels.
- Post-Infection, the IgM levels rise only when the latent VZV is reactivated.
- IgG antibodies are 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.
- Viral detection is done by finding VZV in a blood, vesicle fluid, or tissue sample. Detection is done by culturing the virus or by detecting its genetic material (VZV DNA).
VZV DNA testing
Direct Fluorescent Antibody (DFA)
- DFA test detects the presence of VZV in the cells in the skin lesion using a labeled antibody. It is rapid but less specific and sensitive than DNA testing.