Sore throat – infectious and non infectious causes, red flag symptoms and signs, risk stratification, investigations, empirical management
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sore throat pharyngitis management
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Sore Throat: A Clinical Reference
1. Causes
Infectious Causes
Viral (majority of cases — ~70–80% of adults, higher in children)
| Pathogen | Syndrome | Estimated % of pharyngitis |
|---|---|---|
| Rhinovirus (100+ types) | Common cold | 15–20% |
| Coronavirus (3+ types) | Common cold | >5% |
| Adenovirus (types 3, 4, 7, 14, 21) | Pharyngoconjunctival fever | ~6% |
| Herpes simplex virus 1 & 2 | Gingivitis, stomatitis, pharyngitis | ~4% |
| Parainfluenza virus (1–4) | Common cold, croup | ~2% |
| Influenza A & B | Influenza | ~2% |
| RSV | Bronchiolitis, pharyngitis | 1–2% |
| Coxsackievirus A (herpangina) | Vesicular pharyngitis | <1% |
| Epstein-Barr virus | Infectious mononucleosis | <1% (1–6% in young adults) |
| Cytomegalovirus | Mono-like syndrome | <1% |
| HIV-1 | Acute retroviral syndrome | <1% |
| SARS-CoV-2 | COVID-19 | Variable |
Bacterial
| Pathogen | Syndrome | Estimated % |
|---|---|---|
| Streptococcus pyogenes (GABHS) | Pharyngitis, tonsillitis, scarlet fever | 10–23% |
| Fusobacterium necrophorum | Pharyngitis, Lemierre's syndrome | 5–10% |
| Group C/G streptococci | Pharyngitis | 3–6% |
| Neisseria gonorrhoeae | Pharyngitis | <1% |
| Corynebacterium diphtheriae | Diphtheria (pseudomembrane) | <1% |
| Arcanobacterium haemolyticum | Pharyngitis ± rash | <1% |
| Mycoplasma pneumoniae | Atypical pharyngitis with bronchopulmonary sx | <1% |
| Chlamydia pneumoniae | Atypical pharyngitis | <1% |
| Anaerobes (Bacteroides, Fusobacterium) | Peritonsillar/deep space infection | Polymicrobial |
| Treponema pallidum | Secondary syphilis | <1% |
Fungal
- Candida spp. — cottage-cheese-like plaques that scrape off and bleed; seen in immunosuppressed patients, neonates, inhaled corticosteroid users.
Non-Infectious Causes
| Category | Examples |
|---|---|
| Gastro-oesophageal reflux | Laryngopharyngeal reflux — chronic hoarseness, globus, morning symptoms, no fever |
| Allergic/irritant | Post-nasal drip (allergic rhinitis), dry air, smoke, chemical inhalation |
| Neoplastic | Head and neck malignancy (tongue base, larynx, thyroid, lymphoma/leukaemia) — persistent unilateral sore throat, weight loss, dysphagia |
| Autoimmune/inflammatory | Thyroiditis (de Quervain's), Sjögren's syndrome |
| Referred pain | Acute coronary syndrome, pericarditis, myocarditis presenting as throat pain |
| Trauma | Foreign body (fishbone, bone fragment), caustic ingestion, intubation, neck haematoma |
| Drug-induced | Chemotherapy-induced mucositis, ACE-inhibitor-related angioedema |
| Kawasaki disease | Children — fever ≥5 days, strawberry tongue, rash, cervical lymphadenopathy |
| Stevens-Johnson syndrome | Mucositis + skin blistering — drug reaction |
Harrison's (2025) explicitly states: "Sore throat is not synonymous with pharyngitis and can also be caused by submandibular space, retropharyngeal and peritonsillar abscesses, thyroiditis, gastroesophageal reflux, tumors, and postnasal drainage."
2. Red Flag Symptoms and Signs
These indicate critical or emergent pathology requiring immediate assessment and possible airway management:
🚨 Critical (Airway-Threatening)
- Stridor at rest — epiglottitis, retropharyngeal abscess, angioedema, croup
- Drooling / inability to swallow secretions — epiglottitis ("tripod position")
- Trismus — deep space infection (peritonsillar/parapharyngeal abscess, Ludwig's angina)
- Muffled "hot potato" voice — supraglottic obstruction, peritonsillar abscess
- Neck stiffness + swelling — Ludwig's angina, parapharyngeal/retropharyngeal abscess, expanding haematoma
- Respiratory distress — any cause of upper airway compromise
- Uvular deviation — peritonsillar abscess (uvula deviated away from affected side)
- Rigors / severe systemic toxicity — bacteraemia, Lemierre's syndrome, sepsis
⚠️ Emergent (Requires Urgent Investigation)
- Unilateral persistent sore throat not responding to penicillin — consider N. gonorrhoeae, malignancy, Lemierre's
- Visible neck mass — abscess, lymphoma, thyroid malignancy, leukaemia infiltration
- Persistent symptoms >5 days without improvement
- Odynophagia severe enough to prevent oral intake → dehydration
- Pseudomembrane on tonsillar/pharyngeal surface — diphtheria
- Referred jaw or ear pain with palpable neck mass
- Symptoms in immunocompromised host
- Suspected foreign body ingestion
Features Favouring Serious Bacterial/Suppurative Complications
- Marked unilateral tonsillar swelling with fluctuance → peritonsillar abscess
- Bulging posterior pharyngeal wall → retropharyngeal abscess
- Submandibular/sublingual floor-of-mouth induration → Ludwig's angina
- Septic jugular vein thrombophlebitis (neck pain + fever + pulmonary emboli) → Lemierre's syndrome
3. Risk Stratification — The Modified Centor (McIsaac) Score
This stratifies the probability of Group A Streptococcal (GAS) pharyngitis:
| Criterion | Points |
|---|---|
| History of fever (>38°C) | +1 |
| Tonsillar exudates or swelling | +1 |
| Tender anterior cervical lymphadenopathy | +1 |
| Absence of cough | +1 |
| Age 3–14 years | +1 |
| Age 15–44 years | 0 |
| Age ≥45 years | −1 |
Probability of GABHS by score:
| Score | GABHS probability | Recommended action |
|---|---|---|
| 0 or −1 | 2–7% | No test, no antibiotics |
| 1 | 3–13% | No test, no antibiotics |
| 2 | 8–22% | Perform rapid antigen test (RADT) |
| 3 | 19–38% | Perform RADT |
| 4–5 | 41–>50% | Empirical antibiotics OR RADT |
Rosen's EM notes: "the prevalence of GAS is greater than 50% in patients with a score of 4 or higher."
Features that increase viral likelihood (reducing Centor score relevance):
- Rhinorrhoea, sneezing, cough, hoarseness, conjunctivitis — all suggest viral aetiology.
Features suggesting infectious mononucleosis (EBV) over GAS:
- Posterior cervical or posterior auricular lymphadenopathy
- Splenomegaly
- Palate petechiae + gelatinous uvula
- Age 15–30 years
4. Investigations
Bedside
| Test | Purpose |
|---|---|
| Rapid Antigen Detection Test (RADT) / Optical Immunoassay | First-line GAS test; sensitivity ~60–80%, specificity ~90–97% |
| Throat swab for culture (5% sheep blood agar) | Gold standard for GAS (sensitivity 96%); results in 24–48h; use if RADT negative with high clinical suspicion (especially children) |
| Monospot (heterophile antibody test) | Screening for EBV/infectious mononucleosis (may be falsely negative in first week) |
| NAAT (nucleic acid amplification test) | Higher sensitivity than RADT for GAS; also available for gonorrhoea, Chlamydia |
Blood Tests (for complex or severe presentations)
| Test | Indication |
|---|---|
| FBC | Lymphocytosis with atypical lymphocytes (>10%) — EBV mononucleosis; WCC for severity of infection |
| EBV serology (VCA IgM/IgG, EA, EBNA) | Confirm EBV if monospot negative but clinical suspicion high |
| HIV antigen/antibody (4th-gen) | Acute retroviral syndrome if exposure history + systemic symptoms |
| ASO titre | Retrospective evidence of prior GAS — not useful acutely |
| CRP / ESR | Systemic inflammation; useful in suspected complications |
| Blood cultures | Suspected bacteraemia, Lemierre's, severe sepsis |
| Gonococcal NAAT or culture (pharyngeal swab) | If sexually active, MSM, risk factors |
| TFTs + thyroid ultrasound | If thyroiditis suspected |
Imaging (reserved for suspected complications)
| Study | Indication |
|---|---|
| Lateral soft tissue neck X-ray | Quick assessment — retropharyngeal widening at C2 (>7 mm in adults); epiglottis "thumb sign" |
| Contrast CT neck | Test of choice for peritonsillar abscess, retropharyngeal/parapharyngeal abscess; ring-enhancing fluid collection confirms abscess vs cellulitis |
| Transcervical/intraoral ultrasound | Diagnosis and aspiration guidance for peritonsillar abscess |
| CT chest | Lemierre's syndrome — septic pulmonary emboli |
⚠️ A patient with airway distress should not be sent unobserved for CT scanning. — Tintinalli's
5. Empirical Management
Step 1: Assess for Airway Compromise First
- Signs of stridor, drooling, trismus, respiratory distress → emergent airway preparation + ENT consultation
- Secure airway before disease-specific treatment
Step 2: Symptomatic Treatment (ALL patients)
- Analgesia: Paracetamol or NSAIDs (ibuprofen) — first-line for pain in all pharyngitis
- Saline gargles, humidification, soft foods, warm fluids with honey
- Ensure adequate oral hydration; IV fluids if unable to take orally
- Corticosteroids (adjunct): Single dose of dexamethasone 0.6 mg/kg (max 10 mg) PO/IM — for patients ≥5 years with significant swelling or dysphagia. Reduces pain duration. (Note: Harrison's 2025 cautions that even short steroid courses carry small risks of sepsis, GI bleeding, VTE; routine use is not universally recommended.)
Step 3: Antibiotic Decision by Clinical Scenario
Viral Pharyngitis (majority of cases)
- No antibiotics
- Educate patient: antibiotics confer no benefit for viral pharyngitis, worsen antibiotic resistance, and carry adverse effects
- Reassure: resolves in 3–7 days
GAS Pharyngitis (RADT positive, or high Centor score 4–5)
| Antibiotic | Regimen |
|---|---|
| Penicillin V (1st choice) | 500 mg PO QID or 1000 mg PO BD × 10 days |
| Amoxicillin (preferred in children) | 500 mg PO BD or 1000 mg PO OD × 10 days |
| Benzathine penicillin G (IM, single dose) | 1.2 million units IM — good for adherence concerns |
| Penicillin allergy (non-anaphylactic): Cephalexin | 500 mg PO BD × 10 days |
| Penicillin allergy (non-anaphylactic): Cefadroxil | 1g PO OD × 10 days |
| Severe penicillin allergy: Clindamycin | 300 mg PO TDS × 10 days |
| Severe penicillin allergy: Clarithromycin / Erythromycin | Standard dosing × 10 days |
GAS has never developed resistance to penicillin. 10-day courses are more effective than shorter ones.
Infectious Mononucleosis (EBV)
- No antibiotics (unless secondary bacterial infection)
- Avoid amoxicillin/ampicillin — causes florid maculopapular rash in ~90% of EBV patients
- Rest, analgesia; avoid contact sports (splenomegaly → rupture risk)
- Steroids for severe airway obstruction or thrombocytopenia
Peritonsillar Abscess
- Drainage (needle aspiration or incision) is the definitive treatment
- Antibiotics (post-drainage): penicillin VK or amoxicillin-clavulanate; cover GAS and anaerobes
- If not fluctuant (peritonsillar cellulitis): antibiotics as per GAS protocol
- Severe systemic illness: IV clindamycin 900 mg TDS + ceftriaxone 1 g IV OD
Retropharyngeal / Parapharyngeal Abscess
- Immediate ENT consultation; most require surgical drainage
- Empirical IV antibiotics: piperacillin-tazobactam 3.375 g IV, or ampicillin-sulbactam 3 g IV, or clindamycin 900 mg IV + metronidazole 1 g IV
- Add vancomycin in high-risk patients (MRSA coverage)
Epiglottitis
- Secure airway first; keep patient calm in comfortable position
- ENT + anaesthesia immediately
- Empirical IV antibiotics: ceftriaxone 50 mg/kg (or 1–2 g) IV OD (covers Streptococcus, Staphylococcus, non-typeable H. influenzae)
Ludwig's Angina
- Airway control is priority (awake fibreoptic intubation preferred)
- Broad-spectrum IV antibiotics: penicillin/β-lactam + metronidazole, or piperacillin-tazobactam
- Surgical drainage
Lemierre's Syndrome (Fusobacterium necrophorum)
- Prolonged sore throat + septic emboli + internal jugular vein thrombophlebitis
- IV antibiotics: metronidazole + β-lactam (e.g. ampicillin-sulbactam or piperacillin-tazobactam)
- Anticoagulation is controversial; ENT/ID consultation
Gonococcal Pharyngitis
- Ceftriaxone 500 mg IM single dose (or 1 g if weight >150 kg)
- Treat for concomitant chlamydia if not excluded
Diphtheria
- Diphtheria antitoxin (neutralises free exotoxin) — give empirically, do not wait for culture
- Benzylpenicillin IV or erythromycin; strict isolation
When to Refer / Admit
| Indication | Action |
|---|---|
| Any airway compromise or stridor | Emergency — immediate airway management + ENT |
| Suspected deep space infection (peritonsillar, retropharyngeal, parapharyngeal, Ludwig's) | Admit for IV antibiotics + surgical consultation |
| Lemierre's syndrome | Admit for IV antibiotics ± anticoagulation |
| Unable to maintain oral hydration | Admit for IV fluids |
| Persistent symptoms >5 days without improvement | Reassess, consider complications |
| Suspected malignancy | Urgent ENT/head-and-neck surgery referral |
| Suspected acute HIV | HIV testing, ID referral |
| Immunocompromised host with pharyngitis | Lower threshold for admission |
Sources: Harrison's Principles of Internal Medicine 22E (2025), Rosen's Emergency Medicine 9E, Tintinalli's Emergency Medicine, Textbook of Family Medicine 9E.
Recent guideline note: A 2024 Italian intersociety consensus on acute pharyngitis in children (PMID: 39501298) reinforces that GAS-directed antibiotic treatment should be guided by testing (RADT or culture) rather than clinical features alone, consistent with the Centor/McIsaac framework above.
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