Acute pharyngitis and tonsillitis

Overview

•Most common bacterial cause: *Streptococcus pyogenes* (Group A beta-haemolytic Streptococcus, GABHS) - ~30% of cases; most prevalent in ages 5-15
•Viral causes account for ~70-80% of cases (rhinovirus, adenovirus, EBV)
•Diphtheria - *Corynebacterium diphtheriae*; consider after travel to Eastern Europe/endemic areas

Differential Diagnosis

Key differentials for sore throat
DiagnosisDistinguishing features
Acute tonsillitisBilateral erythematous/exudative tonsils, fever, cervical lymphadenopathy, no cough
Peritonsillar abscess (quinsy)Uvular deviation away from affected side, trismus, drooling, unilateral peritonsillar bulge
Infectious mononucleosis (EBV)Exudative tonsillitis, posterior cervical + generalised lymphadenopathy, splenomegaly, fatigue; adolescents/young adults
DiphtheriaGrey adherent pseudomembrane, travel to endemic area, complete heart block, negative GAS rapid test
EpiglottitisToxic appearance, tripod position, drooling, stridor - do NOT examine throat
Tonsillar carcinomaUnilateral tonsillar enlargement, persistent symptoms, neck mass, otalgia; smoking/HPV risk factors
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Diphtheria: grey pseudomembrane + travel to Eastern Europe + complete heart block on ECG. Notifiable disease - isolate and contact public health immediately.

Management

•All patients: paracetamol and/or ibuprofen for analgesia - avoid aspirin in children under 16 (risk of Reye's syndrome)
•First-line (Centor 3-4): phenoxymethylpenicillin (penicillin V) 500 mg four times daily for 5-10 days
•Penicillin allergy: clarithromycin 250-500 mg twice daily for 5 days
•Second-line (failure/polymicrobial): co-amoxiclav
•EBV confirmed: supportive management - analgesia, rest, hydration; avoid contact sports for at least 4 weeks (splenic rupture risk)
•Peritonsillar abscess (quinsy): same-day ENT referral, IV antibiotics + surgical drainage (needle aspiration first-line); tonsillectomy considered 6 weeks after acute episode
⚠️
Never prescribe amoxicillin or ampicillin if EBV/infectious mononucleosis is possible - causes widespread maculopapular rash in up to 90% of EBV patients. This is a drug-virus interaction, not a true penicillin allergy.

Centor Score

Each criterion scores 1 point. Used to guide antibiotic prescribing. Age adjustment (McIsaac): +1 for ages 3-14.

Criterion
Detail
Tonsillar exudate
White/yellow patches on tonsils
Tender anterior cervical lymphadenopathy
Cervical nodes
Fever >38°C
History or documented
No cough
Absence of cough
•Score 0-1: viral likely - analgesia only, no antibiotic
•Score 2: borderline - consider delayed antibiotic prescription
•Score 3-4: bacterial more likely - antibiotic prescribing appropriate
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Centor score 4 has a positive predictive value of only ~50-60% for GAS - use clinical judgement alongside the score.

Tonsillectomy Referral Criteria

Refer to ENT for consideration of tonsillectomy (SIGN/NICE) when episodes are frequent and significantly disrupt daily life:

•7 or more documented episodes in the preceding year, OR
•5 or more episodes per year for 2 consecutive years, OR
•3 or more episodes per year for 3 consecutive years
•Episodes must be clinically significant - causing school/work absence, requiring medical attention, or antibiotics
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Tonsillectomy is performed far less frequently than previously - evidence for benefit is modest and complications (primary and secondary haemorrhage) are significant. Apply referral criteria strictly.