The Infectious Diseases Society of America (IDSA) has just released a 2012 update of the Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis, its first update in 10 years. Acute pharyngitis is common -- and most episodes, the guideline emphasizes, are not due to group A streptococcus (GAS). That does not, however, mean that patients with non-GAS pharyngitis are not receiving antibiotics. In fact, inappropriate treatment of acute pharyngitis with antibiotics is a major contributor to the rising incidence of antimicrobial resistance. Two articles just published in Archives of Internal Medicine document the continuing problem of overprescribing of antibiotics for viral infections.[2,3] In an invited commentary in Archives, Ralph Gonzales, MD, MSPH, Director of the Program in Implementation and Dissemination Sciences at the University of California, San Francisco, argued that the continuing high rate of antibiotic use is the result of a failure to translate evidence into practice. Medscape spoke with Stanford Shulman, MD, lead author of the IDSA guideline and Professor of Pediatric Infectious Diseases at Northwestern University's Feinberg School of Medicine, about the evidence underpinning this new guideline and its usefulness in helping clinicians to translate this important guideline into practice.
Examining the Evidence
Medscape: Can you briefly review the process used by the guideline authors to evaluate evidence from the last 10 years when developing the updated guideline?
Dr. Shulman: The guideline committee carried out a comprehensive review of the published literature since release of the last document in 2002. Individual members of the guideline committee searched publications related to all topics to be included within the guideline. We included careful evaluation of a Cochrane review that had been published recently related to this topic. We reviewed guidelines of other organizations who make recommendations related to this topic as well to make sure that we understood the nature of other organizational guidelines.
Medscape: Can you describe the strength of the evidence?
Dr. Shulman: I think the evidence is reasonably strong in most situations but certainly not all.
Medscape: The guideline strongly emphasizes the need to confirm a diagnosis of GAS and not to rely on clinical suspicion. The authors then go on to list the signs and symptoms that suggest a viral or bacterial etiology. However, the guideline notes that scoring systems based on clinical signs and symptoms are relatively poor predictors of the presence or absence of GAS. Is there any scenario in which treatment based on clinical suspicion alone is appropriate?
Dr. Shulman: The guideline does provide a list of symptoms that are commonly associated with GAS infections of the throat in addition to a list of separate signs and symptoms related to viral pharyngitis. Having laid out those signs and symptoms that are often present with GAS, it is still clear that those signs and symptoms are not sufficiently reliable or accurate to allow diagnosis of streptococcal pharyngitis to be made on clinical suspicion alone. There are simply too many false positives and some false negatives. With respect to the viral signs and symptoms, patients who have rhinorrhea, cough, mouth ulcers, and hoarseness are very unlikely to have bona fide streptococcal pharyngitis. So we can rely upon their presence to conclude on clinical grounds that the patient does not have a streptococcal pharyngitis and testing is not really indicated.
Is there any scenario in which treatment could be based on clinical suspicion alone? I think that there are a few circumstances where the epidemiology would suggest this is reasonable. For example, if one child in a family has signs and symptoms suggestive of strep and the diagnosis is then confirmed in that child, and a sibling or someone else in the household in short order presents with an identical or very similar clinical illness, it would be reasonable to assume that the same pathogen is in the household and the likelihood of that second child having streptococcal pharyngitis as well would be extremely high. That would be a scenario in which clinical suspicion would enable one to make a diagnosis.
Medscape: The guideline notes that rapid antigen detection tests (RADTs) have sufficient specificity for clinicians to make a decision to treat patients with a positive RADT. However, sensitivity is not ideal, and, therefore, negative RADTs in children, but not adults, should prompt clinicians to obtain a backup throat culture. Is this recommendation applicable to all clinical situations? What about situations where the RADT is obtained despite a clinical suspicion of a viral etiology in order to reassure an anxious parent? Can clinicians reasonably use an RADT to confirm a suspected viral etiology for pharyngitis?
Dr. Shulman: Unfortunately, what one intuitively might think is a very simple situation -- we either have a virus or we have a strep infection and it shouldn't be so complicated -- can become very complicated. The answer to your question is: no. If the clinical clues are all pointing towards a viral etiology, relying upon a rapid test or a culture can be very misleading. This gets us into a discussion of the very complicated problem of the chronic streptococcal carrier. There are many children, and a considerable number of young adults as well, who become at various times colonized in the throat with GAS that does not cause an infection in the sense of making the patient ill. Carriage in chronic carriers persists many months -- 6 and even 12 months has been documented. If the individual who is a chronic carrier gets a cold and has a throat swab done, the throat swab will be positive. A rapid test and even a culture cannot reliably distinguish between a person who has a bona fide streptococcal pharyngitis and one who is a chronically colonized individual who now has an intercurrent viral illness. You can't distinguish those individuals. So, it's really not recommended to do any testing if the clinician really believes that all the signs and symptoms point towards a virus.
What About Carriers?
Medscape: The identification and management of a suspected GAS carrier is one of the thorniest issues discussed in the guideline, which concludes that these individuals need not be identified or treated as they are unlikely to be infectious or to develop GAS complications. However, as you have clearly illustrated, unidentified carriers presenting with acute viral pharyngitis do end up being treated with antibiotics even if the clinician suspects a viral etiology. Is there any evidence that clinicians should attempt to eradicate the carrier state?
Dr. Shulman: On a routine basis, we believe the carrier state is not a serious issue that warrants attempts to eradicate it except in highly selected circumstances such as if there is a history of someone with rheumatic fever in the household and you do not want to have a carrier in the household. In general, it is not necessary. However, the scenario you posed earlier gets to the issue of how does one really establish the diagnosis of a GAS carrier? The patient who comes in with enough symptoms to raise the clinical suspicion of a possible streptococcal pharyngitis should be tested with a rapid test and/or throat culture. If positive, the patient should be treated. A common scenario is a child who, within a brief period of time, say a couple of months, after that initial episode, has repeated illnesses that have prompted throat swabs that are repeatedly positive. That raises the clinical suspicion that perhaps this is a child who really is not having bona fide streptococcal pharyngitis over and over again but may be a chronic streptococcal carrier.
One way to try to clarify that situation is to wait until this child is asymptomatic and in a normal state of health. Then, culture the patient at that point in time. Finding GAS in the throat of the asymptomatic child at that point pretty much clinches the diagnosis of the chronic streptococcal carrier. That can make it easier to deal with future episodes of sore throat. Knowing that a child or an adult is a chronic streptococcal carrier should alter the indications to swab in the future. If a patient who is known to be a carrier has marginal symptoms -- not really highly suggestive of a streptococcal pharyngitis -- that would be a circumstance where it is probably wise not to do any kind of testing. If, however, a child who is a chronic carrier comes in with every symptom that strongly points towards a possible streptococcal pharyngitis, you want to err on the side of caution. You should do a swabbing and testing of that particular child. But I think that you want to use a different scale in terms of whose throat you want to swab and test when you know a patient is a streptococcal carrier.
Medscape: And to clarify -- this is quite different from a recommendation to culture as a test of cure.
Dr. Shulman: That is correct. While some could argue it is similar to a test of cure, it is in very selected patients and very selective circumstances.
Medscape: Should a carrier be cultured subsequently to determine if the carrier state is still present?
Dr. Shulman: There has never been a recommendation that one should do that. There might be selective situations, depending on the epidemiology; for example, a household with someone who is at particularly high risk of acquiring GAS from the carrier -- even though in general we view carriers to be not at all highly contagious. Carriers seem to be at very little risk to themselves in terms of developing complications of strep and at very low risk to their contacts. They do not seem to shed organisms efficiently, in contrast to someone who has a bona fide infection with presumably higher numbers of strep cells that are more actively replicating and more metabolically active and more easily transmitted from patient to patient.
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Cite this: Getting Strep Pharyngitis Right - Medscape - Nov 09, 2012.