What is the procedure for taking a streptococcal pharyngitis (strep throat) test?

From the Guidelines

To take a strep throat test, a healthcare provider will use a rapid antigen test or throat culture, where they swab the back of your throat and tonsils with a sterile cotton swab, and results are available within minutes for a rapid test or 24-48 hours for a throat culture. The test is typically performed by tilting your head back and opening your mouth wide, with the provider using a tongue depressor to hold down your tongue during the swabbing process, which may cause a brief gagging sensation but only lasts a few seconds 1.

Key Points to Consider:

• The test should be done if you have symptoms like severe sore throat, fever, swollen lymph nodes, or white patches on your tonsils, especially without cough or runny nose 1.
• Early testing is important because strep throat requires antibiotic treatment to prevent complications like rheumatic fever or kidney inflammation 1.
• If you suspect strep throat, avoid self-diagnosis and seek medical care promptly, as antibiotics should be started within 48 hours of symptom onset for best results 1.
• The modified Centor criteria, which include fever by history, tonsillar exudates, tender anterior cervical adenopathy, and absence of cough, can be used to determine the likelihood of a bacterial cause, but patients who meet fewer than 3 Centor criteria do not need to be tested 1.

Testing Methods:

• Rapid antigen detection tests (RADTs) are available and provide results faster than throat cultures, but may have a lower sensitivity 1.
• Throat cultures are more accurate but take longer to produce results, typically 24-48 hours 1.
• The use of anaerobic incubation and selective culture media may increase the proportion of positive culture results, but data are conflicting, and the increased cost and effort may not be justified 1.

Importance of Accurate Diagnosis:

• Accurate diagnosis is crucial to prevent unnecessary antibiotic use and to ensure appropriate treatment for strep throat, which can help reduce the risk of complications and the spread of the infection 1.
• Clinicians should be aware of the limitations of RADTs and throat cultures and use clinical judgment when interpreting test results 1.

Recent Guidelines:

• The 2016 guidelines from the American College of Physicians and the Centers for Disease Control and Prevention recommend antibiotic therapy only for patients with a positive streptococcal test result 1.
• The guidelines also emphasize the importance of using clinical scoring criteria, such as the modified Centor criteria, to determine the likelihood of a bacterial cause and to guide testing and treatment decisions 1.

From the Research

Strep Throat Test Methods

• Throat culture is considered the diagnostic standard for streptococcal pharyngitis 2
• Rapid antigen detection testing is also available, with improved sensitivity and specificity 2, 3
• The modified Centor score can be used to help physicians decide which patients need no testing, throat culture/rapid antigen detection testing, or empiric antibiotic therapy 2

Steps to Take a Strep Throat Test

• A careful physical examination and patient history is the starting point for diagnosing GABHS 4
• Screening of all children with pharyngitis for Centor criteria, followed by a rapid antigen detection test (RADT) to guide decision for antibiotic administration 3
• If the RADT result is negative, a throat culture is recommended in children and adolescents 5

Diagnostic Criteria

• Fever, tonsillar exudate, cervical lymphadenitis, and patient ages of 3 to 15 years increase clinical suspicion of group A beta-hemolytic streptococcal infection 5
• A cough is more suggestive of a viral etiology 5
• The presence of one, two, three or four clinical criteria can increase the sensitivity of the RADT 3