Last updated: August 1, 2019
Topic: FamilyChildren
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pharyngitis, also known as strep throat, is most often caused bacterially by
Streptococcus pyogenes, also known as part of group A Streptococcus, or GAS
(CDC, 2016).  This type of bacteria is
beta-hemolytic that belongs to the Lancefield serogroup A (Medscape, 2017).  Acute pharyngitis accounts for about 12
million ambulatory calls in the United States and is extremely common,
especially in the winter and early spring (Medscape, 2017). 

strep pharyngitis presents with a common set of symptoms, which are often
diagnosed based on symptoms in association with in-office lab tests.  The condition is spread directly from person
to person, especially in places such as schools, child daycares or large public
spaces (CDC, 2016).  The common symptoms
include sore throat, fever over 100.4 degrees F, exudates noted on the tonsils
and adenopathy of cervical nodes (Choby,
2009).  Some patients also present
with a scalatiniform rash which will begin within the first couple days of the
infections and causes an erythematous rash on the neck and limbs (Medscape).

some of symptoms can create an extensive differential, a diagnostic test of
Group A step bacteria can be confirmed by a rapid antigen detection test (RADT)
or a throat culture (CDC, 2016).  RADTs
are speedy and allow for a clinician to know whether or not antibiotics are the
correct line of treatment for each patient. 
However, RADTs can be higher in cost and are reported to have a lower
sensitivity compared with other cultures (Medscape, 2017).  RADT ranges from 90%-99% specificity, and
approximately 70% sensitive, but the AAP recommends that a negative RADT result
needs to be confirmed with a throat culture (Choby, 2009). 

ease of a throat culture or RADT allow for clinicians to differentiate the
causes of a sore throat in many different settings, such as Urgent Care or a
primary care setting.  The sample is
obtained from the posterior pharynx or tonsils (Medscape, 2017).  In the 1950s, acute rheumatic fever was the
main focus of treating pharyngitis. 
Since the incidence of rheumatic fever has substantially decreased, the
focus was shifted to treating GAS infections with tests such as RADT (Stewart, 2014).  Today, newer RADT uses what is called optical
immunoassay (OIA) technology to find the carbohydrates in the cell wall.  This allows for a sensitivity that is much
closer to that of a throat culture (Medscape, 2017). Even beyond this
technology is a test which uses nucleic acid to identify the bacteria, and is
said to be about 95%-100% specific and 86%-95% sensitive (Medscape, 2017). 

A strep pharyngitis is very prevalent in children, which makes a quick
diagnosis extremely important to keep the infection from spreading from child
to child.  Although throat culture is
considered to be the gold standard for diagnosis of bacterial strep, the rapid
test is much quicker, as the throat culture has a 24-48 hour turn around
(Medscape, 2017).  Often, clinicians are
guilty of prescribing antibiotics based on a false positive RADT test without
confirming with a throat culture.  This
is a large component in the overuse of antibiotics in a clinical setting.  With the help of both critical physicians and
other staff, these types of errors can be decreased and more correct diagnosis’
and treatments will become ubiquitous. 



Bacterial Pharyngitis Workup. (2017, November 17).

Retrieved January 21, 2018, from

Choby, B.A. (2009, March 01). Diagnosis and Treatment of
Streptococcal Pharyngitis. Retrieved              
January 21, 2018, from

Pharyngitis (Strep Throat). (2016, September 16).

Retrieved January 21, 2018, from                         

Stewart, E.H., Davis, B., Clemans-Taylor, B.L.,
Littenberg, B., Estrada, C.A., & Centor, R.M.       (2014). Rapid Antigen Group A Streptococcus Test to Diagnose
Pharyngitis: A Systemic                 
Review and Meta- Analysis. Retireved January 21, 2018, from             med