A doctor can usually diagnose shingles during a physical exam. But in rare cases, you may need a test to confirm a shingles diagnosis. PCR tests are the most accurate, but there are also other options.

If you’ve ever had chickenpox, the varicella-zoster virus (VZV) has remained dormant in your nervous system since then. VZV causes chickenpox. If this virus reactivates later in your life, it can also cause shingles.

Shingles is a disease that affects 1 in 3 people in the United States.

Most people who get shingles are over age 50. But children, teens, and adults of any age can all get shingles. While uncommon, people vaccinated against chickenpox may also develop this condition.

A doctor can usually diagnose shingles, also called herpes zoster, by visually examining your symptoms. In some instances, though, testing may be beneficial.

In this article, we’ll review the reasons you might need additional testing. We’ll also discuss and describe the types of tests a doctor may recommend.

Hallmark symptoms of the varicella-zoster virus

The main feature of chickenpox is an itchy rash of red blisters that appears all over the body. It may also cause fever, headache, and fatigue.

Unlike chickenpox, a shingles rash is usually limited to one side of your body, usually on one side of the torso (trunk of the body) or one side of the face. This rash of blister-like sores can be extremely painful.

Before a shingles rash appears, you may experience early symptoms like tingling, itching, and pain where the rash will form.

Other symptoms may include an upset stomach, fever, chills, and headache. Eye pain may accompany a shingles rash that forms on the face.

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A healthcare professional may recommend testing if you are immunodeficient or at risk of complications from shingles or chickenpox. At-risk populations include:

  • pregnant people
  • infants born to people with an infection
  • people with conditions that affect the immune system, such as HIV or AIDS

A doctor may also recommend a test if you have unusual symptoms. Examples include if you have no rash or a rash on an area of the body less likely to experience one.

You may also want to test for VZV if you aren’t sure whether you are immune to the virus that causes shingles.

Clinicians can sometimes confuse shingles with other conditions. A test may help rule out other conditions, such as:

According to the Centers for Disease Control and Prevention (CDC), the polymerase chain reaction (PCR) swab test is the most useful test for shingles. PCR tests detect genetic material from a virus or other organism. PCR tests for shingles can detect DNA from VZV.

During a PCR test, a healthcare professional will use a sterile needle to “unroof” the top of a blister. They’ll then roll a swab over the base of the shingles lesion to extract a sample. If all your blisters are already scabbed, the healthcare professional may remove a scab and send it for testing.

If you have shingles-like pain without a blistering rash, a healthcare professional may use a swab to collect saliva from your mouth. But the CDC notes that testing saliva or other bodily fluids may lead to false negative results.

The healthcare professional will send your PCR sample to a laboratory for analysis under a microscope. Lab technicians put the sample in a machine that can detect even very small traces of the virus.

A healthcare professional may recommend a PCR test if you have a weakened immune system and have a shingles-like rash on your body somewhere other than your trunk or face. The test is also beneficial for diagnosing shingles in people who received the chickenpox vaccine.

The CDC notes that other tests may provide a more rapid turnaround time than PCR tests, but they are not as effective or reliable.

Like the PCR test, a DFA test uses a swab to check for VZV. This test can often provide a quick and specific result.

But DFA is much less sensitive than PCR and may provide a false negative. Although DFA may provide a quick result, you may still need a PCR test to confirm.

The VZV IgG avidity test (aka VZV titer test) is a blood test that checks for antibodies to VZV. Experts may recommend this test to check if you have immunity to VZV.

A healthcare professional will extract a small amount of blood from a vein, usually in your arm. They will then send the sample to a lab for analysis.

Blood tests are not as accurate as PCR tests in detecting shingles. Still, a doctor may use a blood test if you have no blisters to provide a sample for a PCR test.

For this test, a healthcare professional will scrape a fresh blister with a scalpel and send it to a lab for analysis. The test looks for certain cells caused by herpesviruses like VZV but it cannot test specifically for VZV.

How do I prepare for a shingles test?

A healthcare professional may test for shingles in their office. Instead, they may recommend that you go to a walk-in lab for testing. Either way, there is no specific preparation needed for these tests.

Are there any risks or side effects from a shingles test?

Shingles tests are safe and do not have any side effects. If you get a blood test, you may bleed slightly after the test or see some bruising at the insertion site of the needle.

How long does it take to get results from a shingles test?

You may have to wait several days for PCR or titer test results. According to the Minnesota Department of Health, it usually takes 2 business days.

Although a doctor can typically diagnose shingles through a physical exam, they may recommend a test in certain cases.

You may need a test if you are at high risk of complications from shingles. This includes people with weakened immune systems and people who are pregnant.

If you have symptoms of shingles, talk with a doctor to determine if testing is right for you.