From the Guidelines
There is no reliable blood test to diagnose shingles, as serology is not useful for diagnosis of varicella-zoster virus (VZV) infection, according to the most recent evidence 1. The diagnosis of shingles is typically based on the characteristic painful, blistering rash that follows a dermatomal pattern (along a nerve pathway).
- The most accurate diagnosis can be made by detecting VZV DNA in blister material scraped or swabbed from a disrupted skin lesion using nucleic acid amplification technology tests, which are specific and sensitive (both approaching 100%) 1.
- Commercial tests for VZV IgG have suboptimal sensitivity, and available tests are not optimized to detect antibody to the vaccine virus 1.
- While PCR (polymerase chain reaction) blood tests can detect VZV DNA in the bloodstream, this is less commonly used than PCR tests of fluid from skin lesions, and a negative test result does not exclude the diagnosis of varicella encephalitis 1.
- The presence of CSF varicella zoster virus IgM antibodies may also be present in patients with a negative CSF varicella zoster virus PCR result, but this is not a reliable method for diagnosing shingles 1.
- The management of shingles typically involves antiviral therapy, such as high-dose IV acyclovir, oral acyclovir, famciclovir, and valacyclovir, which can help reduce the severity and duration of symptoms 1.
From the Research
Blood Tests for Diagnosing Shingles
- There are several blood tests that can help diagnose shingles, including tests that detect varicella-zoster virus (VZV) antibodies and DNA [ 2, 3 ].
- These tests can be used to detect VZV infection, but their sensitivity and specificity may vary 3.
- Some studies have shown that combining PCR and serology can achieve optimal laboratory sensitivity in diagnosing herpes zoster from serum 3.
Types of Blood Tests
- Enzyme immunoassay (EIA) can detect VZV IgM antibodies in acute and convalescent zoster sera 3.
- Complement fixation (CF) test and IgG indirect fluorescent antibody assay (IgG IFA) can detect VZV antibodies in paired zoster sera 3.
- Real-time polymerase chain reaction (PCR) can detect VZV DNA in acute zoster sera 3.
- Nucleic acid detection methods, such as PCR, can be used to detect VZV in blood and other specimens 4.
Limitations and Future Directions
- Serological methods alone may have limited value for early diagnosis of zoster, as they often require convalescent serum and have insufficient sensitivity 3.
- Further studies are needed to improve the sensitivity and specificity of blood tests for diagnosing shingles, particularly in atypical cases 3.
- The development of more sensitive assays and tests that can distinguish between different clinical entities may be possible using newly identified VZV antigens 2.