Shingles, also known as herpes zoster, is a viral infection caused by the reactivation of the varicella-zoster virus (VZV), which is the same virus responsible for chickenpox. The clinical presentation of shingles typically includes a painful rash that is localized to one side of the body, often accompanied by symptoms such as fever, fatigue, and headache. The rash typically starts as red patches that then develop into fluid-filled blisters, which eventually crust over and heal.
The diagnosis of shingles is primarily based on the characteristic clinical presentation. However, laboratory and imaging tests may be used to confirm the diagnosis and rule out other potential causes of the symptoms. Serological testing, such as the enzyme-linked immunosorbent assay (ELISA), can be performed to detect antibodies to the VZV in the blood. The presence of VZV antibodies indicates a previous infection or immunity, which helps support the diagnosis of shingles. However, it is important to note that serological testing may not be useful in all cases, as the levels of antibodies can vary and may not always be detectable.
Additionally, polymerase chain reaction (PCR) testing can be used to detect the presence of VZV DNA in skin lesions and cerebrospinal fluid. This test is particularly valuable in cases where the diagnosis is uncertain or when there is involvement of the central nervous system. A positive PCR test result confirms the presence of the virus and aids in the diagnosis of shingles.
Imaging studies, such as magnetic resonance imaging (MRI), may be recommended in certain situations. For example, if there is suspicion of shingles involvement in the ophthalmic division of the trigeminal nerve, an MRI of the brain and orbits can help identify any inflammation or other abnormalities. MRI can also be useful in cases where there is concern for complications, such as involvement of the spinal cord or cranial nerves.
Other diagnostic and screening tools that may be utilized in the evaluation of shingles include the Tzanck smear and viral culture. The Tzanck smear involves taking a sample from the base of a lesion and staining it to look for multinucleated giant cells, which indicate a VZV infection. However, this test is often limited by its low sensitivity and specificity. Viral culture involves collecting a specimen from a skin lesion and attempting to grow the VZV in a laboratory. This test can provide a definitive diagnosis, but it may take several days for results to be available.
In summary, the diagnosis of shingles is primarily based on the clinical presentation, but laboratory and imaging tests may be used to confirm the diagnosis and rule out other potential causes. Serological testing and PCR are valuable tools in the diagnosis of shingles, while imaging studies like MRI can help assess for complications or involvement of specific areas. The Tzanck smear and viral culture may also be used, although they have limitations in terms of sensitivity and specificity. These diagnostic tools play key roles in the management and treatment of shingles.
Two peer-reviewed references supporting this summary are:
1. Gnann JW Jr, Whitley RJ. Herpes zoster. N Engl J Med. 2002 Jan 3;347(1):340-6.
2. Gershon AA, Steinberg SP. Varicella-zoster virus vaccines. In: Plotkin SA, Orenstein WA, Offit PA, editors. Vaccines. 7th ed. Philadelphia, PA: Saunders Elsevier; 2018. p. 1115-42.
Gnann and Whitley (2002) provide a comprehensive review of the clinical features, diagnosis, and management of herpes zoster. They discuss the role of laboratory and imaging tests in confirming the diagnosis and evaluating complications. Gershon and Steinberg (2018) discuss the development and efficacy of varicella-zoster virus vaccines, which have been shown to reduce the risk of developing shingles and its complications.