By Dr Ananya Mandal, MD
Diagnosis of Shingles of Herpes Zoster may be made only on the basis of clinical examination of the lesion, symptoms and a past history of chicken pox infection.
Characteristically, Shingles produces pain and a rash on one side of the body. (9)
Rarely, however, Shingles can occur without a rash. Or the rash may not be noticed or it may be mistaken for something else. (10)
Sometimes, tests may be needed to confirm the diagnosis. A sample of the skin may be taken to examine for the infection.
In addition, routine blood tests may show a rise in the numbers of white blood cells and antibodies or fighter molecules against the chickenpox. (1)
Tests for Shingles
Tests are not normally needed for the diagnosis of Shingles; however, there are certain conditions under which tests may be carried out.
- If the doctor is unsure about the diagnosis of Shingles
- If the doctor feels you are prone to developing complications
- If you have a weakened immune system
- If your symptoms are not responding to medication
- If your symptoms include an inability to control your bladder or bowel
- If the doctor is concerned that your eyes may be being affected by the condition (8)
There are several tests for Shingles, these include Electromyography, Spinal tap, MRI imaging and so forth. (2, 3, 4, 5, 6)
This is a test that looks at the adequate functioning of a muscle and the nerves that connect it.
The test involves passing a very thin needle electrode through the skin into the muscle. This will pick up the electrical activity given off the muscle that is recorded on a computer.
On contraction or movement of the muscle, the activity changes and the change is recorded.
There may be a little pain during the test due to the needle and a slight bruising or tenderness afterwards but these are mild side effects.
Spinal tap or lumbar puncture
The brain and spine are bathed in Cerebrospinal fluid (CSF). This is collected with a long thin needle inserted at the base of the spine. The fluid is normally clear.
An MRI image of the brain and spine
An MRI (magnetic resonance imaging) scan of the brain uses powerful magnets to create pictures of the brain.
A contrast dye may be injected to get a clearer picture of the brain.
Nerve conduction velocity (NCV)
This test is done to determine the extent of damage to the facial and other nerves. It checks how fast an impulse travels through a nerve.
Surface electrodes that appear as patches are placed on the skin over nerves at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve.
The impulse is recorded by the other electrodes. A computer measures the speed of the impulse travel via various nerves.
Blood tests for chicken pox antibodies
There are two ways to obtain blood for chicken pox virus testing.
The first is a Blood Spot Method. In this test a drop of blood is collected from the tip of the finger and allowed to dry on a special strip to be used for testing.
This strip is tested for the virus at the laboratories.
The other method is to collect whole blood. The blood is collected in serum separator vacutainer or vaccuum tubes.
The sample is allowed to clot fully be allowing to stand in room temperature for half an hour.
Then the sample undergoes processing like centrifugation that separates the blood cells from the clear serum. The sample is then shipped to the laboratories at -20 degrees. (7)
Skin tests may be performed for detection of varicella zoster virus.
A Polyester Swab Method is preferred.
A sterile needle is used to break open a blister. A swab is then used to vigorously swab the base of the lesion. It collects the fluid without causing bleeding.
The swab should be made of synthetic fibers, such as polyester, because cotton fibers make diagnosis difficult.
The swabs are placed in sealed containers and shipped to laboratories for analysis.
In addition a Glass slide method may be used. The slide is used to scrape the side of the lesion. Cells and fluid is gathered onto the slide.
Further crusts or scabs may also be sent for diagnosis.
The test applied in the laboratory is polymerase chain reaction (PCR) that looks for the chicken pox virus DNA in the specimen, tissues, blood, CSF or biopsy samples. (7)
Edited by April Cashin-Garbutt, BA Hons (Cantab)
What is Shingles?
Last Updated: Jun 7, 2013