Chickenpox is a common and highly contagious viral infection, especially among children. It usually causes an itchy rash covered with small, red blisters, along with fever and general discomfort. If you or your child develops symptoms that look like chickenpox, you might wonder, “How do they test for chickenpox?” This article will walk you through the various ways healthcare providers diagnose chickenpox, from simple physical exams to advanced lab tests, all explained in an easy-to-understand way.
Recognizing Chickenpox: The First Step in Diagnosis
Most often, chickenpox is diagnosed by a healthcare provider simply by looking at the characteristic rash and considering other symptoms like fever and tiredness. The rash typically starts on the face, chest, and back, then spreads to the rest of the body. Because the rash is so distinctive, many cases don’t require lab tests for confirmation.
However, in some cases-such as when the rash looks unusual, symptoms are mild, or the patient is at higher risk (like pregnant women or immunocompromised individuals)-additional testing may be needed to confirm the diagnosis.
Laboratory Tests for Chickenpox: What Are the Options?
When a lab test is necessary, there are several methods to detect the varicella-zoster virus (VZV), the virus that causes chickenpox. These tests either look for the virus itself or for antibodies your body produces in response to the infection.
1. PCR (Polymerase Chain Reaction) Test
– This is the most accurate and fastest test for detecting chickenpox.
– It looks for the genetic material (DNA) of the virus in a sample taken from the fluid inside a blister or from a skin lesion.
– The sample is collected by gently swabbing an open blister.
– Results can come back quickly, often within a day or two.
2. Viral Culture
– In this test, cells from a blister swab are grown in a lab to see if the virus multiplies.
– It is very accurate but takes several days to get results.
– Because of the time it takes, it’s less commonly used than PCR.
3. Direct Fluorescent Antibody (DFA) Test
– This test uses a special fluorescent dye and microscope to detect the virus in blister fluid.
– It is faster than viral culture but not as sensitive as PCR.
– It is useful for rapid diagnosis when PCR is not available.
4. Antibody Blood Tests
– These tests check your blood for antibodies against VZV.
– There are two main types of antibodies tested:
– IgM antibodies indicate a recent or current infection.
– IgG antibodies show past infection or vaccination, meaning immunity.
– Blood is drawn from a vein, and the test can help confirm if you have had chickenpox before or if you are currently infected.
How Are These Tests Done? What to Expect
– Swab Test: A healthcare provider gently swabs the fluid from a blister using a cotton swab. This is quick and painless.
– Blood Test: A small needle is used to draw blood from a vein, usually in your arm. You might feel a quick pinch.
Both types of tests are simple and usually take less than five minutes to perform. No special preparation is needed before testing, and risks are minimal-some slight bruising or discomfort might occur after a blood draw, but blister swabbing is risk-free.
Special Tests: The Tzanck Smear
There is also a less common test called the Tzanck smear, where cells from the base of a blister are scraped and examined under a microscope. This test looks for characteristic multinucleated giant cells, which indicate infection with herpes viruses, including VZV. However, it cannot distinguish chickenpox from other similar infections and is rarely used today because PCR is more accurate.
When Is Testing Necessary?
Testing isn’t usually required for healthy children or adults with typical chickenpox symptoms. But doctors may order tests if:
– The rash isn’t typical or is mild.
– The patient is pregnant or has a weakened immune system.
– There is a need to confirm immunity before organ transplants or other medical procedures.
– There is concern about complications or severe disease.
What Do Test Results Mean?
– Positive for VZV or antibodies: Confirms current or past chickenpox infection or vaccination.
– Negative for VZV or antibodies: Suggests no prior exposure or immunity, meaning the person is susceptible to chickenpox.
– IgM Positive: Indicates recent or active infection.
– IgG Positive: Indicates past infection or immunity from vaccination.
If you test positive and are at risk for complications, your doctor might prescribe antiviral medications to reduce symptoms and prevent serious problems.
Can You Test for Chickenpox at Home?
Currently, there are no reliable FDA-approved at-home tests for chickenpox. If you suspect chickenpox, it’s best to see a healthcare provider for proper evaluation and testing. Early diagnosis helps manage symptoms and prevent spreading the virus to others.
Summary
Chickenpox is usually diagnosed by its distinctive rash, but lab tests can confirm the infection when needed. The PCR test is the most accurate and fastest way to detect the virus, while blood tests check for antibodies indicating current or past infection. Testing is especially important for people with unusual symptoms or those at higher risk. Always consult a healthcare professional if you suspect chickenpox for proper diagnosis and care.
Chickenpox testing is straightforward and effective, helping you get the right care quickly and safely. If you or a loved one shows signs of chickenpox, don’t hesitate to seek medical advice.