Sore throat – infectious and non infectious causes, red flag symptoms and signs, risk stratification, investigations, empirical management
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pharyngitis management guidelines
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Sore Throat: A Comprehensive Clinical Overview
1. Causes
Infectious Causes
Viral (majority — 30–80% of cases)
| Virus | Presentation |
|---|---|
| Rhinovirus / Coronavirus | Common cold; mild pharyngitis with coryza |
| Adenovirus | Pharyngoconjunctival fever (pharyngitis + conjunctivitis) |
| Parainfluenza | Common cold, croup |
| Influenza A & B | Widespread outbreaks; nonexudative pharyngitis + systemic features |
| Epstein-Barr virus (EBV) | Infectious mononucleosis: exudative pharyngitis, posterior cervical lymphadenopathy, splenomegaly |
| Cytomegalovirus (CMV) | Mono-like illness; heterophile-negative |
| Herpes simplex 1 & 2 | Pharyngitis, gingivostomatitis, painful vesicles/ulcers |
| Coxsackievirus A | Herpangina (vesicular eruption on soft palate), hand-foot-mouth disease |
| HIV (acute retroviral syndrome) | Fever, pharyngitis, rash, mucocutaneous ulcers, nontender lymphadenopathy |
| RSV / Measles | Pharyngitis as part of systemic illness |
Bacterial (5–10% adults; 20–40% children)
| Organism | Notes |
|---|---|
| Group A β-haemolytic Streptococcus (GAS/GABHS) | Most common bacterial cause; complications include rheumatic fever, glomerulonephritis, peritonsillar abscess |
| Non-GAS streptococci (Groups B, C, G) | Similar presentation; glomerulonephritis is a sequela, but not rheumatic fever |
| Fusobacterium necrophorum | Young adults (15–45 yrs); primary agent of Lemierre syndrome (septic jugular thrombophlebitis) |
| Arcanobacterium haemolyticum | Teens; urticarial/scarlatiniform rash sparing face, palms, and soles |
| Neisseria gonorrhoeae | Sexually transmitted; white-yellow tonsillar exudate |
| Corynebacterium diphtheriae | Grey-green pseudomembrane; toxin causes myocarditis, neuritis; consider in unvaccinated/travellers |
| Mycoplasma pneumoniae / Chlamydia pneumoniae | Pharyngitis as part of atypical lower respiratory illness; crowded settings |
| Treponema pallidum | Secondary syphilis: pharyngitis ± localised adenopathy; primary syphilis: painless oral ulcer |
| Yersinia enterocolitica | Pharyngitis + enterocolitis |
| Francisella tularensis | Tularemia oropharyngeal form; false-positive monospot |
| Mixed anaerobes | Vincent angina (ulcerative gingivitis) |
Fungal
- Candida spp. — immunocompromised patients (HIV, chemotherapy, prolonged antibiotics, inhaled corticosteroids)
Adjacent Infections Presenting as Sore Throat
- Peritonsillar abscess, retropharyngeal abscess, parapharyngeal abscess, epiglottitis, Ludwig angina
Non-Infectious Causes
| Category | Examples |
|---|---|
| Neoplastic | Pharyngeal/tonsillar malignancy (unilateral tonsil enlargement, persistent symptoms) |
| Autoimmune | PFAPA syndrome, SLE, Behçet disease, Kawasaki disease |
| Mechanical/trauma | Foreign body, thermal burn, heroic snoring |
| Medication-induced | ACE inhibitor-related angioedema, methimazole/carbimazole (agranulocytosis), chemotherapy mucositis |
| Neurogenic pain | Glossopharyngeal neuralgia, Eagle syndrome |
| Thyroiditis | Referred pain to throat |
| Stevens-Johnson syndrome | Mucosal involvement |
| Pericarditis/myocarditis | Referred throat pain |
— ROSEN's Emergency Medicine, Table 61.1; K.J. Lee's Essential Otolaryngology, p. 685
2. Red Flag Symptoms and Signs
These indicate potentially life-threatening deep space infections, airway compromise, or severe systemic illness:
| Red Flag | Concern |
|---|---|
| Stridor | Airway compromise (epiglottitis, retropharyngeal abscess, angioedema) |
| Drooling / inability to swallow | Airway oedema or deep space infection |
| Muffled / "hot potato" voice | Peritonsillar or parapharyngeal abscess |
| Trismus (limited mouth opening) | Peritonsillar or parapharyngeal abscess |
| Sniffing position / tripod posturing | Epiglottitis |
| Neck stiffness or torticollis | Retropharyngeal abscess, meningitis |
| Uvular deviation | Peritonsillar abscess (uvula deviates away from abscess) |
| Unilateral tonsillar swelling | Abscess, malignancy |
| Toxic appearance / sepsis | Invasive GAS, Lemierre syndrome, necrotising fasciitis |
| Hypoxia | Severe airway compromise |
| Progressive symptoms > 1 week | Malignancy, abscess, atypical infection |
| Dyspnoea | Supraglottic/glottic oedema |
| Inability to open mouth | Parapharyngeal / masticator space abscess |
| Anterior neck swelling / "bull neck" | Diphtheria, Ludwig angina |
Stridor is a sign of true airway emergency. It is critical to determine severity, rate of onset, and progression. — ROSEN's Emergency Medicine, p. 883
3. Risk Stratification: Modified Centor Score (McIsaac Score)
Used to estimate the likelihood of GAS pharyngitis and guide testing/treatment decisions.
| Criterion | Points |
|---|---|
| History of fever (>38°C) | +1 |
| Tonsillar exudates | +1 |
| Tender anterior cervical lymphadenopathy | +1 |
| Absence of cough | +1 |
| Age 3–14 years | +1 |
| Age >45 years | −1 |
| Score | Estimated GAS Prevalence | Recommended Action |
|---|---|---|
| 0 or −1 | ~5–10% | No testing or antibiotics |
| 1 | ~10–15% | No testing or antibiotics |
| 2 | ~20–30% | Rapid antigen test (RADT) |
| 3 | ~33–38% | RADT; treat if positive |
| 4–5 | >50% | RADT; strong consideration for empirical treatment |
Testing and treatment should also be avoided when overt viral features are present (cough, rhinorrhoea, oral vesicles/ulcers, conjunctivitis) — a positive test in this context suggests GAS carriage rather than active infection. — ROSEN's Emergency Medicine / Goldman-Cecil Medicine, Table 397-2
4. Investigations
First-Line
| Test | Indication / Notes |
|---|---|
| Rapid antigen detection test (RADT) | Sensitivity ~80–90%, high specificity; positive result warrants treatment |
| Throat culture (swab) | Gold standard; sensitivity 90–95%; 18–48 hrs; use if RADT negative in children/adolescents |
| Nucleic acid amplification test (NAAT) | Sensitivity ~97.5%, specificity ~95%; preferred over RADT where available |
Selective / Second-Line
| Test | Indication |
|---|---|
| Monospot (heterophile antibody test) | Suspected EBV mononucleosis; low sensitivity in young children (<2 yrs) and early illness; negative test does not exclude EBV |
| EBV IgM/IgG serology | Confirms EBV if monospot negative but clinical suspicion high |
| FBC / blood film | Atypical lymphocytes suggest EBV/CMV; left shift in bacterial/TSS |
| Liver enzymes (ALT/AST) | EBV hepatitis (if right upper quadrant tenderness) |
| CMV IgM/IgG | Heterophile-negative mononucleosis |
| HIV fourth-generation test | Acute retroviral syndrome suspected |
| GC/Chlamydia PCR (throat swab) | Sexually active patients with atypical presentations |
| Syphilis serology (RPR/TPHA) | Secondary syphilis; unilateral tonsillar lesion |
| Contrast-enhanced CT neck | Suspected deep space infection (retropharyngeal/parapharyngeal abscess) — cannot be reliably excluded clinically |
| Transcervical or intraoral USS | Peritonsillar abscess diagnosis and drainage guidance |
| CXR / blood cultures | Diphtheria, Lemierre syndrome, sepsis |
| Lateral neck X-ray | Suspected epiglottitis (if patient stable; "thumbprint sign") |
Adult patients with Centor ≥3 should have RADT; in adults with negative RADT, backup throat culture is generally not required because of low GAS incidence and low rheumatic fever risk. In children, backup culture is recommended after negative RADT. — Goldman-Cecil Medicine
5. Empirical Management
Management Algorithm
Step 1: Rule Out Airway Compromise (Priority)
- If stridor, drooling, muffled voice, sniffing posture, or hypoxia → prepare for difficult airway
- Maintain upright position; IV access; O₂ monitoring
- Empirical steroids + antibiotics
- Immediate ENT / anaesthesiology / surgical consultation
- Advanced airway management via difficult airway algorithm
Step 2: Symptomatic Treatment (All Cases)
- Analgesia: Paracetamol or NSAIDs (regularly, not PRN)
- Corticosteroids: Single dose dexamethasone 0.6 mg/kg (max 10 mg) PO or IM for patients >5 yrs with severe pain/dysphagia. Reduces pain duration and severity. (Supported by ESCMID guidelines; not routinely endorsed by IDSA for uncomplicated pharyngitis)
- Hydration: Ensure adequate oral intake; IV fluids if severe odynophagia/dehydration
Step 3: Antibiotic Therapy — Condition-Specific
| Pathogen / Condition | First-Line Treatment | Alternative |
|---|---|---|
| GAS pharyngitis | Penicillin V (phenoxymethylpenicillin): 500 mg PO BD × 10 days (adult); Benzathine penicillin G IM 1.2 million units (>27 kg) single dose | Amoxicillin 500 mg TDS × 10 days; Cefuroxime 250 mg BD × 10 days |
| Penicillin allergy (GAS) | Azithromycin 500 mg/day × 3 days; Clindamycin 300 mg QID × 10 days | |
| Recurrent GAS | Clindamycin 300 mg QID × 10 days; Amoxicillin-clavulanate 875 mg BD × 10 days | |
| Group G Streptococcus | Penicillin G IM | |
| Fusobacterium / Lemierre syndrome | Piperacillin/tazobactam; OR ceftriaxone 1g q24h + metronidazole 500 mg q8h | |
| Epiglottitis | Ceftriaxone 50 mg/kg (or 1g) IV OD; OR ampicillin/sulbactam 3g q6h | Levofloxacin 750 mg OD (penicillin allergy) |
| Retropharyngeal/Parapharyngeal abscess / Ludwig angina | Ampicillin/sulbactam 3g q6h; OR penicillin G + metronidazole 500 mg QID | Surgical drainage required |
| Peritonsillar abscess (PTA) | Drainage (definitive); Penicillin + metronidazole or clindamycin IV (parenteral: clindamycin 10 mg/kg or 900 mg TID + ceftriaxone 50 mg/kg or 1g q24h) | |
| Diphtheria | Antitoxin (urgent) + Penicillin/erythromycin | |
| Gonococcal pharyngitis | Ceftriaxone IM/IV | |
| Viral pharyngitis | No antibiotics — supportive care only | |
| Oral candidiasis | Nystatin suspension; Fluconazole for refractory/systemic |
For EBV mononucleosis: avoid amoxicillin/ampicillin (risk of maculopapular rash). Steroids may reduce tonsillar enlargement when swallowing or respiratory symptoms are attributed to enlarged tonsils. Counsel about splenic rupture risk — avoid contact sports until splenomegaly resolves.
Antibiotic Goals in GAS Treatment
- Shorten illness duration (by ~1 day)
- Prevent suppurative complications (PTA, sinusitis, otitis media)
- Prevent transmission (contagious period reduced from 2 weeks to 24 hours post-antibiotics)
- Prevent rheumatic fever (antibiotics must be started within 10 days of symptom onset)
- Note: Antibiotics do not reduce risk of post-streptococcal glomerulonephritis
Antibiotic Stewardship
- Viruses cause most pharyngitis; do not treat based on symptoms and exam alone
- Centor 0–1: no antibiotics, no testing
- Avoid empirical antibiotics without testing in adults (Centor ≥3 only)
- Patient education is key: explain lack of symptomatic benefit from antibiotics and risks (GI side effects, resistance, anaphylaxis, fungal infections)
Summary Table
| Domain | Key Points |
|---|---|
| Most common cause | Viral (rhinovirus, coronavirus, adenovirus) |
| Most important bacterial cause | GAS (S. pyogenes) |
| Risk stratification tool | Modified Centor / McIsaac score |
| Gold standard test | Throat culture (backup to RADT) |
| First-line antibiotic (GAS) | Penicillin V × 10 days |
| Absolute red flags | Stridor, drooling, trismus, uvular deviation, toxic appearance |
| Never do | Amoxicillin/ampicillin in suspected EBV; antibiotics for purely viral presentations |
| Deep space infections | Require contrast CT, ENT consultation, parenteral broad-spectrum antibiotics ± surgical drainage |
Sources:
- ROSEN's Emergency Medicine, Chapters 19 & 61
- Goldman-Cecil Medicine International Edition, Chapters 269 & 397
- K.J. Lee's Essential Otolaryngology, Chapter on Acute Pharyngitis
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