Although the earliest appearance of shingles symptoms is sometimes confused with hives (raised areas of itchy skin),
bedbug bites, or scabies (skin infection by scabies mite), the classic pain and blistering in a band on one side of the body may be all that is necessary for a doctor to clinically diagnose herpes zoster infection (shingles). This is the most frequent way shingles is
presumptively diagnosed. The rash may occasionally extend outside of this band or, infrequently, to the other side of the body. Rarely, there may be only pain in a dermatome band without a rash.
- The doctor may decide to do tests to confirm that a patient has shingles. However, these tests listed below are not always necessary, as a presumptive diagnosis based on clinical findings is often definitive enough for diagnosing shingles.
- A Tzanck smear, which is less commonly performed now
since newer diagnostic techniques are available
(see below), involves opening a blister and putting fluid and skin cells from it on a
glass slide. After using a special stain, the slide is examined under the microscope for characteristic viral
changes in the cells. This method is unable to distinguish between VZV and
herpes simplex virus (HSV), however. VZV causes shingles and chickenpox. HSV
types may cause cold sores or
- Viral cultures or special antibody tests, such as DFA (direct fluorescent antibody), of the blister may reveal varicella-zoster virus. DFA results are often available within hours. This test differentiates between VZV and HSV
viral types. Viral cultures may take up to
two weeks or more to yield results.
- Skin biopsy, taking a piece of skin rash and looking at it under the microscope, is another possible way to diagnose herpes zoster. A culture of the biopsied tissue may be done if there are no intact blisters to culture. Also, viral DNA (deoxyribonucleic acid) may be detected using
PCR (polymerase chain reaction) on the tissue taken from the biopsy. This test is expensive and not routinely used
to diagnose shingles.
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