While most cases of pharyngitis are caused by viruses and resolve without specific therapy, pharyngitis is among the most common syndromes prompting outpatient antimicrobial therapy, in part because it is difficult to distinguish viral infections from bacterial infections. An updated guideline from IDSA provides recommendations for diagnosing group A streptococcal pharyngitis, or GAS. Miriam Barshak, MD, FIDSA, senior author of the guideline, answers questions from Science Speaks about the new recommendations, highlighting key updates and the importance of appropriate testing.
Who is this updated guideline primarily intended for? Who will find it most useful?
It is primarily intended for clinicians who are assessing patients who present with a complaint of sore throat — including physicians and others who work in pediatrics, internal medicine, family medicine, emergency medicine, urgent care, otolaryngology, pharmacy and others. I expect it will be most useful for these professionals but also useful for others, including public health workers, laboratory medicine/microbiology specialists, and patients and their family members.
What are the key updates or changes compared to previous guidelines for assessing GAS pharyngitis?
The key update is the recommendation to use a clinical scoring system as part of the evaluation of patients with sore throat. The principal utility of a scoring system is to identify patients with low probability of group A streptococcal pharyngitis, in whom further evaluation by diagnostic testing is unlikely to be helpful. Until now there has not been a clear standard for clinical practice in determining who to test for strep.
This means that some providers are essentially testing everyone who comes in with a sore throat, while others are using some degree of clinical judgement that may be biased in ways that may lead to either overtesting or undertesting. Overtesting is more likely, which may lead to higher costs of care and overtreatment, since testing is imperfect; some tests that are positive will be falsely positive. Overtreatment has risks of side effects and promoting resistance to antibiotics over time.
Why is appropriate testing for GAS pharyngitis important? What are the risks of unselective testing?
Appropriate testing is important for individual patients so that they are being tested only when the test is likely to be useful in guiding decisions about treatment. Because no test is perfect, we know that testing may mistakenly identify people who don’t have strep and also may miss those who do have strep. Unselective testing, therefore, can lead to both underdiagnosis and overdiagnosis, which can lead to higher costs of care as well as side effects from unnecessary treatment for individual patients and also higher risks of promoting resistance to antibiotics over time in the population.
What else should clinicians know about this update?
- The recommendation to use a scoring system is conditional, with low certainty of evidence. The data for scoring systems in the literature were limited by small sample size, a lack of uniformity in outcome measures, incomplete data and not being contemporary. More work is needed in the current era.
- The recommendation to use a scoring system doesn’t apply to children under the age of 3 years, since the signs and symptoms of GAS may be different in this age group.
- High-risk individuals should be strongly considered for testing even if their clinical scores are low. Examples of high-risk individuals include those presenting with a sore throat who have had household exposure to GAS (e.g., living or sleeping in the same indoor shared space as a person diagnosed with GAS infection), a history of a previous rheumatic fever diagnosis, or symptoms or signs suggestive of complicated local or systemic GAS infection (e.g., peritonsillar or retropharyngeal abscess, scarlet fever and/or toxic shock syndrome).
- Given the lack of evidence favoring any particular scoring system, clinicians and patients may favor clinical scoring systems that do not include laboratory test(s).
What areas will future planned updates to this guideline address?
Other topics related to diagnostic testing — including initial and follow-up testing — as well as topics related to the choice of treatment and duration of treatment, including in patients who are allergic to penicillin, are planned.
To learn more, see the full guideline, “Clinical Practice Guideline Update by the Infectious Diseases Society of America on Group A Streptococcal (GAS) Pharyngitis.”