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For further information, see CMDT Part 8-20: Pharyngitis & Tonsillitis

Key Features

Essentials of Diagnosis

  • Sore throat

  • Fever

  • Anterior cervical adenopathy

  • Tonsillar exudate

  • Goal is to treat group A β-hemolytic streptococcus infection to prevent rheumatic sequelae

General Considerations

  • Group A β-hemolytic streptococci (Streptococcus pyogenes) are the most common bacterial cause of exudative pharyngitis

  • The main concern is to determine whether the cause is group A β-hemolytic streptococcal infection (GABHS), because of the complications of rheumatic fever and glomerulonephritis

  • A second public health policy concern is to reduce the extraordinary cost (in both dollars and development of antibiotic-resistant Streptococcus pneumoniae in the United States associated with unnecessary antibiotic use)

  • About one-third of patients with infectious mononucleosis have secondary streptococcal tonsillitis, requiring treatment

  • Ampicillin should routinely be avoided if mononucleosis is suspected because it induces a rash


  • Pharyngitis and tonsillitis account for > 10% of all office visits to primary care clinicians and 50% of outpatient antibiotic use

Clinical Findings

Symptoms and Signs

  • Centor diagnostic criteria

    • Fever > 38°C

    • Tender anterior cervical adenopathy

    • Lack of cough

    • Pharyngotonsillar exudate

  • Sore throat may be severe, with odynophagia, tender adenopathy, and a scarlatiniform rash

  • Hoarseness, cough, and coryza are not suggestive of this disease

  • Marked lymphadenopathy and a shaggy white-purple tonsillar exudate, often extending into the nasopharynx, suggest mononucleosis, especially if present in a young adult

Differential Diagnosis

  • Viral pharyngitis

  • Epstein-Barr virus (EBV)/infectious mononucleosis

  • Primary HIV infection

  • Candidiasis

  • Necrotizing ulcerative gingivostomatitis (Vincent fusospirochetal disease)

  • Retropharyngeal abscess

  • Diphtheria

  • Neisseria gonorrhoeae

  • Mycoplasma

  • Anaerobic streptococci

  • Corynebacterium haemolyticum

  • Epiglottitis


Laboratory Tests

  • The presence of the four Centor diagnostic criteria strongly suggests GABHS

  • When two or three of the four are present, there is an intermediate likelihood of GABHS

  • When zero or one Centor criterion is present, GABHS is unlikely; throat culture or rapid antigen detection testing of throat swab is not necessary

  • With about 90% sensitivity, lymphocyte to white blood cell ratios of > 35% suggest EBV infection and not tonsillitis


  • Patients with zero or one Centor criteria should not receive antibiotics

  • Patients with two or three Centor criteria whose throat cultures or rapid antigen detection testing show positive results should receive antibiotic treatment

  • Patients who have four Centor criteria can receive empiric therapy without throat culture or rapid antigen detection testing


  • Benzathine penicillin intramuscular injection

    • 1.2 million units once is optimal but painful

    • Used for noncompliant patients

  • Analgesic, anti-inflammatory drugs (aspirin, acetaminophen, corticosteroids)

  • Oral antibiotics

    • Penicillin V potassium (250 mg three times daily or 500 mg twice daily orally for 10 days) or ...

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