Strep Throat Tests

Strep Throat Basics

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QuickVue Rapid Strep Test

QuickVue Rapid Strep Test
Strep Test Pictures QuickVue Rapid Strep Test. Vincent Iannelli, MD

When your child has a sore throat, you are probably used to the fact that your Pediatrician will swab your child's throat and then come back and either say it is strep throat or just a virus. After reviewing these pictures, you will understand how your doctor can use those swabs to do a rapid strep test and/or a strep culture to help determine if your child does indeed have strep throat.

A rapid strep test is a fast and easy way to diagnose strep in your Pediatrician's office.

A quick diagnosis of strep is important, because chlildren with strep throat need antibiotics to help them get better and to prevent them from getting rheumatic fever. On the other hand, they do not need antibiotics to treat the common viruses that can also cause sore throats.

Testing for strep is the only way to tell if your child has strep or a virus, and while it can take 1-2 days to get results from a strep culture, you can get the results from a rapid strep test in about 5 minutes.

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Positive Rapid Strep Test

A Positive QuickVue Rapid Strep Test
Strep Test Pictures A Positive QuickVue Rapid Strep Test. Vincent Iannelli, MD

Here is a picture of a positive rapid strep test, indicating that a child likely has an infection caused by the Group A Strep bacteria.

A positive strep test is not an absolute indication of a strep infection, as some people are strep carriers, in which the strep bacteria is growing in their body, but is not causing any symptoms. These children often always test positive for strep, even when they don't have classic strep symptoms.

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A Positive Rapid Strep Test

A Positive Rapid Strep Test
Strep Test Pictures A Positive Rapid Strep Test. Vincent Iannelli, MD

This close-up of the rapid strep test shows a positive result, indicated by the dark red line.

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A Negative Rapid Strep Test

A Negative Rapid Strep Test
Strep Test Pictures A Negative Rapid Strep Test. Vincent Iannelli, MD

The lack of a red line under the blue line shows that this is a negative strep test.

Since rapid strep tests are not 100% accurate, it is still recommended that children with negative rapid strep tests have a backup strep culture to make sure that they really don't have strep throat.

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A Positive Culture for Strep

A Positive Culture for Strep
Strep Test Pictures A Positive Culture for Strep. Vincent Iannelli, MD

A positive culture for the Group A Strep bacteria from a child with strep throat.

Note the beta hemolysis on the blood agar plate and inhibition of growth around the bacitracin disk.

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A Negative Culture for Strep

A Negative Culture for Strep
Strep Test Pictures A Negative Culture for Strep. Vincent Iannelli, MD

A negative culture for the Group A Strep bacteria.

Note how there is no beta hemolysis on the blood agar culture plate and how the growth on the agar goes right up to and around the bacitracin disk. Remember that the Group A strep bacteria that causes strep throat is inhibited by the bacitracin disk.

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