Tonsillitis

Tonsillitis, infection of the palatine tonsils, is a common condition in children and adults. There is no clear distinction between tonsillitis and pharyngitis, and so the condition may also be called pharyngitis or tonsillopharyngitis.

In 70% of cases tonsillitis is caused by viruses and is one part of a viral upper respiratory tract infection, which affects multiple parts of the upper respiratory tract. In 30% of cases, mostly in children, tonsillitis is isolated and bacterial, caused by streptococcus pyogenes, also called group A streptococcus (GAS). This is called streptococcal pharyngitis or strep throat. When a patient presents with symptoms of pharyngitis or tonsillitis it's important to determine whether it's viral or streptococcal. Both are self-limiting, but antibiotic treatment for streptococcal infection shorten the disease and prevent potentially severe complications.

Clinical features

Tonsillitis causes pain on swallowing which may radiate to the ear. The clinical features of viral and streptococcal tonsillitis are slightly different:

Features more commonly seen in viral infection	Features more commonly seen in streptococcal infection
Symptoms of infection of other parts of the upper respiratory tract, like rhinitis, conjunctivits, cough, hoarseness	Absence of cough
No fever or just a slight fever	Fever >38.5
Enlarged tonsils without coating	Enlarged tonsils with white coating
Visible erythema of the oropharynx	Absence of erythema of the oropharynx
No or just slightly tender cervical lymph nodes	Enlarged and tender cervical lymph nodes

Diagnosis and evaluation

The diagnosis of tonsillitis is clinical. The distinction between viral and streptococcal etiology can often also be made clinically with the use of the Centor criteria. One point is awarded for each criterium:

• Absence of cough
• Fever >38.5
• Enlarged tonsils with white coating
• Enlarged and tender cervical lymph nodes

When 4/4 criteria are positive, the pre-test probability of streptococcus is more than 50%, and a test isn't necessary. When 0-1/4 criteria are positive, the probability is low and testing isn't necessary. When the criteria are 2 or 3, the pre-test probability is intermediate, and so a test is recommended.

Testing is usually by point-of-care rapid tests which have high sensitivity and specificity. It can also be achieved by PCR or culturing, but this is rarely necessary.

Taking a blood test is usually unneccessary, but can be useful if there is doubt whether the infection is viral or bacterial. Inflammatory markers are usually more elevated in case of bacterial infection, and so a CRP > 75 or leukocyte count of > 15 points to streptococcus.

Management

For viral pharyngitis, no specific treatment exists. Symptomatic treatment involves paracetamol and local anaesthetic-containing lozenges.

For streptococcal pharyngitis, antibiotics are indicated. Streptococcus pyogenes is sensitive to penicillin, and so oral penicillin V is the first choice.

Complications

Streptococcal pharyngitis may (rarely), especially if untreated, lead to severe complications, including peritonsillar abscess, parapharyngeal abscess, scarlet fever, rheumatic fever, poststreptococcal glomerulonephritis. PANDAS is a very rare condition which may be caused by GAS infection, characterised by acute onset OCD and tics.

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