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GROUP A STREPTOCOCCAL PHARYNGITIS TESTING
GUIDELINES AND PROCEDURAL LIMITATIONS
By Irwin Z. Rothenberg, MBA, MS, CLS(ASCP), Technical Writer / Quality Advisor, COLA Resources, Inc.
Strep tests are used to determine if a person with a sore throat
(pharyngitis) has strep throat, an infection of the throat and tonsils
caused by the bacteria Streptococcus pyogenes, also called Group A
Streptococcus (GAS), or if the sore throat is caused by a virus.
The majority of sore throats (70%-85%) are actually viral in
nature, and will resolve without treatment within a few days.
However, it is important to determine when sore throats are
caused by GAS, since this is the most common bacterial cause of
acute pharyngitis, responsible for 5%–15% of sore throat visits
in adults and 20%–30% in children. It is most common in
children ages 5 to 15 years old (over 50 % of the cases occur
within this age bracket); it is very contagious; and needs to be
identified as soon as possible, and treated with antibiotics.
Accurate diagnosis of streptococcal pharyngitis followed by
appropriate antimicrobial therapy is important for the
prevention of acute rheumatic fever; for the prevention of
suppurative complications (e.g. peritonsillar abscess, cervical
lymphadenitis, mastoiditis, and, possibly, other invasive
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infections); to improve clinical symptoms and signs; for the
rapid decrease in contagiousness; for the reduction in
transmission of GAS to family members, classmates, and other
close contacts of the patient; to allow for the rapid resumption
of usual activities; and for the minimization of potential
adverse effects of inappropriate antimicrobial therapy.
Fortunately, most streptococcal infections are now routinely
diagnosed and treated through rapid strep testing, these
complications are rare in the United States, but they do still occur.
Establishing the Diagnosis of GAS Pharyngitis
1. Swabbing the throat and testing for GAS pharyngitis by rapid
strep test and/or throat culture should be performed because
clinical features alone do not reliably discriminate between
GAS and viral pharyngitis except when overt viral features
like runny nose, cough, oral ulceration, and/or hoarseness
are present. In children and adolescents, negative rapid strep
tests should be backed up by a throat culture; however,
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