Tonsillitis and Peritonsillar Abscess Workup

Updated: Jan 19, 2017
  • Author: Udayan K Shah, MD, FACS, FAAP; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Workup

Approach Considerations

Tonsillitis and peritonsillar abscess (PTA) are clinical diagnoses. Testing is indicated when group A beta-hemolytic Streptococcus pyogenes (GABHS) infection is suspected. Throat cultures are the criterion standard for detecting GABHS. For patients in whom acute tonsillitis is suspected to have spread to deep neck structures (ie, beyond the fascial planes of the oropharynx), radiologic imaging using plain films of the lateral neck or CT scans with contrast is warranted. In cases of PTA, CT scanning with contrast is indicated.

Test the patient's family members for the presence of streptococcal antibodies to detect carriers of group A Streptococcus (especially family members who are immunocompromised).

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Lab Studies

Throat cultures are the criterion standard for detecting group A beta-hemolytic Streptococcus pyogenes (GABHS). GABHS is the principal organism for which antibiotic therapy (sensitivity 90-95%) is definitely indicated. Growing concerns over bacterial resistance make monitoring acute tonsillitis with throat swabs for culture and sensitivity an important endeavor. Relying only on clinical criteria, such as the presence of exudate, erythema, fever, and lymphadenopathy, is not an accurate method for distinguishing GABHS from viral tonsillitis. A Monospot serum test, CBC count, and serum electrolyte level test may be indicated.

A rapid antigen detection test (RADT), also known as the rapid streptococcal test, detects the presence of GABHS cell wall carbohydrate from swabbed material and is considered less sensitive than throat cultures; however, the test has a specificity of 95% or more and produces a result in significantly less time than that required for throat cultures. A negative RADT requires that a throat culture be obtained before excluding GABHS infection.

A culture or RADT is not indicated in most cases following antibiotic therapy for acute GABHS pharyngitis. Routine testing of asymptomatic household contacts is similarly not usually warranted.

Serum may be examined for antistreptococcal antibodies, including antistreptolysin-O antibodies and antideoxyribonuclease (anti-DNAse) B antibodies. Titers are useful for documenting prior infection in persons diagnosed with acute rheumatic fever, glomerulonephritis, or other complications of GABHS pharyngitis.

Laboratory evaluation in chronic tonsillitis relies upon documentation of results of pharyngeal swabs or cultures taken during prior episodes of tonsillitis. The usefulness and cost of throat swabs for pharyngitis are debated.

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Imaging Studies

Routine radiologic imaging is not useful in cases of acute tonsillitis. For patients in whom acute tonsillitis is suspected to have spread to deep neck structures (ie, beyond the fascial planes of the oropharynx), radiologic imaging using plain films of the lateral neck or CT scans with contrast is warranted.

In cases of peritonsillar abscess (PTA), CT scanning with contrast is indicated in general [13] for unusual presentations (eg, an inferior pole abscess) and for patients at high risk for drainage procedures (eg, patients with coagulopathy or anesthetic risk).

CT scanning may be used to guide needle aspiration for draining PTAs after an unsuccessful surgical attempt and for draining abscesses that are located in unusual locations and are anticipated to be difficult to reach with standard surgical approaches. Hatch and Wu mentioned ultrasonography as another means of guidance in PTA drainage. [14]

A study by Huang et al indicated that ultrasonography is an accurate means of evaluating patients for PTA, finding that compared with patients diagnosed with PTA via traditional examination methods and/or CT scanning, those who were diagnosed with transcervical ultrasonography demonstrated significant reductions in surgical drainage and length of hospital stay. [15]

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