Self-Checks/At-Home Testing
Scarlet fever is the presence of a rash on the body when you have an infection with Group A streptococcus bacteria causing a sore throat. Strep throat is the common name that is given for this infection. Scarlet fever simply means you or your child has a rash with strep throat.
Although this may seem like a simple thing that could be diagnosed at home, it is not.
White patches may be present in the throat with strep, but they may also be present when a sore throat is caused by other bacteria or viruses and a person can have strep with no white patches. So, it’s best to visit a healthcare provider to get a diagnosis.
Labs and Tests
A healthcare professional can perform quick, painless tests to confirm a scarlet fever diagnosis.
Rapid Strep Test
Rapid strep tests are—as the name suggests—very quick. Results are usually available in less than 10 minutes.
A swab is rubbed in the back of the oropharynx and then placed in a solution that indicates the presence, or lack of, the Group A strep bacteria. Although these tests are quick and convenient, they are not always 100 percent accurate.
Throat Cultures
Throat cultures are considered the gold standard for diagnosing scarlet fever and strep throat. The sample is obtained the same way as a rapid strep test—a swab that resembles a long Q-tip is passed over the back of the throat in the oropharynx. For this test, the sample is typically sent off to an outside lab where it is allowed to “grow” to determine if Group A streptococcus bacteria is present.
This test is more accurate but it takes longer, so many healthcare providers choose to use throat cultures as a backup diagnostic tool.
Differential Diagnoses
A person with a sore throat and rash can have any number of illnesses. A vast majority of rashes and sore throats are caused by viruses. However, if you or your child has this combination of symptoms, it’s important to see your healthcare provider for an accurate diagnosis—even more so if a fever is present as well.
The rash of scarlet fever typically begins in the creases of the body—the neck, underarms, and groin—and then spreads to the torso and the rest of the body. It may start off looking like large flat red bumps and then will change to the appearance of red sandpaper. The cheeks often have a rosy appearance as well.
Children with scarlet fever or strep throat that are left untreated may develop rheumatic fever, but it is rare in adults. Another potential complication of these illnesses is post-streptococcal glomerulonephritis, which is a very complicated sounding name for an inflammation of the kidneys after an infection with Group A strep. Your healthcare provider should be able to differentiate between all of these and provide appropriate treatment.
