How do doctors diagnose strep throat?

A healthcare provider can typically diagnose the condition with a rapid strep test or a throat culture. Treatment usually includes antibiotics.

Can you diagnose strep throat at home?

While an at-home rapid strep throat test will give you a result in minutes , you'll need to contact a healthcare provider for a diagnosis of the infection and to get a prescription for antibiotics.

What is the proper way to test for strep?

Using a clean, soft cotton swab, they'll lightly brush over the back of the throat, around the tonsils, and over any red or sore areas to collect a sample . Sometimes, they use two swabs so the second swab can be sent for a throat culture if the rapid strep test results are negative.

How Strep Throat Is Diagnosed (2024)

Diagnosis ofstrep throatcannot be based solely on clinical signs and symptoms, and additionaltestsare required for positive identification of theStreptococcus pyogenesbacteria that cause the condition. A rapid strep test can yield same-day results, but it may take a couple ofdays to get the results of a throat culture, which is more accurate. A definitive diagnosisis important because treatment can help prevent possible long-term complications, such as heart and kidney disease.

Self-Checks

The early signs and symptoms of strep throat overlap with those of most upper respiratory infections. While you can't diagnose yourself with strep, you can look for the following, which may hint that strep throatcouldbe affecting you or your child:

Swelling in the back of the throat
White spots or white patches on the back of the throat
Small red or purple spots inside your mouth

There are a few important symptoms that could indicate a persistent or worsening infection:

High fever(above 101 degrees)
Persistent fever (lasting longer than 24 hours)
Rash on the chest, arms, or neck
Redness on theface
Trouble breathing
Decreased amount of urine;change in the color of urine

Labs and Tests

Because strep throat causes signs and symptoms that are so similar to those of viral infections and other bacterial infections, the best way to confirm the diagnosis is with a laboratory test. Tests can detect either theStreptococcus pyogenesorganism or markers that signal the presence of the organism in the back of your throat.

Throat Culture

A throat culture has long been considered the diagnostic gold standard of strep throat infection, with the main disadvantage being a 24- to 48-hour delay in culture results.

The throat culture is performed by collecting bacteria from the back of the throat using a long swab. The sample is placed on special plates made of sheep blood mixed with bacteria growth media (called sheep blood agar plates)and allowed to grow in a lab.

Streptococcus pyogenes has a unique feature that allows it to break open red blood cells. When the bacteria aregrown on these plates, there will bea clearing of red blood cells on the petri dish ifStreptococcus pyogenes bacteria is present in the sample.

Rapid Antigen Detection Tests

A rapid antigen testis typically done in the doctor's office and isalsoperformed by swabbing the back of the throat. The bacterial swab is subjected to enzymes or acid to extract parts of the Strep pyogenesbacteria, which are calledantigens. Positive or negative, you should get the results in about 10 to 20 minutes.

Rapid antigen tests have much lower sensitivity than throat cultures, which means that they are more likely to mistakenly missstrep infection than throat cultures are.

It is estimated that rapid antigen tests have about a 14 to 20%false-negativerate. For this reason, if there is a strong chance of strep throat infection, it is recommended that a negative result from a rapid antigen test be followed up with a throat culture (for confirmation).

Rapid antigen detection tests are not associated with a false positive rate, which means that if they come back positive, there ishigh certainty that you have a strep throat infection.

Negative Strep Throat Test: What Else Mimics Strep?

Imaging

Imaging tests are notroutine in the diagnosis of uncomplicated strep throat infection.However,tests such as X-ray, CT, MRI, or ultrasound may be necessary to evaluate serious complications of strep throat infections, such as kidney or heart involvement. These complications are rare and primarily seen in untreated patients.

Differential Diagnoses

Most upper respiratory infections can begin with the same signs and symptoms as strep throat. Here are some of the illnesses that are considered when you are being evaluated for a possiblestrep throat:

Epstein-Barr virus (mononucleosis):This infection also involvesmuscle aches and a sense of feeling run down.
Influenza (the flu)
Pneumonia:This is a lung infection that causes coughing, wheezing, and shortness of breath.
Bronchitis:An acute or chronic infection or inflammation of the bronchi causesa productive cough and may cause shortness of breath.
Mycobacteria infection:This lung infection causes a cough and wheezing.
Fusobacterium necrophorum: This infection of the lungs usually causes more severe symptoms than strep throat.
Systemic illness: It can affect any organ of the body and may begin with symptoms similar to those of an early strep throat infection.
Appendicitis: This condition may begin with a fever and aches, but usually causes abdominal pain as well.
Arthritis: This chronic inflammatory disease causes symptoms similar to those of the complications of strep infection

Less often, primary HIV, HSV, gonorrhea, diphtheria, or tularemia can cause symptoms similar to those of strep throat.

Frequently Asked Questions

Can I diagnose strep throat at home?

No. Early symptoms are too similar to other upper respiratory illnesses, so a lab test for bacteria is necessary to confirm the diagnosis and start antibiotics, such as penicillin.
How long is strep contagious after being diagnosed?

If your strep test comes back positive, your doctor will start you on antibiotics. You’re no longer considered contagious after 24 hours on antibiotics. However, finish the entire course of treatment to avoid complications, like rheumatic fever.
What are the differences between a viral sore throat and strep?

Both cause pain and make it hard to swallow, but unlike a viral infection, strep usually includes swollen lymph nodes and a high fever. You may also have white spots on the throat or red spots in the mouth, a rash on the neck, and symptoms that last more than 48 hours.

How Strep Throat Is Treated