What is the differential diagnosis and treatment for a patient presenting with a sore throat?

Differential Diagnosis for Sore Throat

The differential diagnosis for acute sore throat is predominantly viral (60-85% of cases), with Group A β-hemolytic streptococcus (GABHS) being the most important bacterial cause requiring antibiotic therapy, accounting for 15-30% in children and 5-15% in adults. 1

Infectious Causes

Viral Etiologies (Most Common)

• Respiratory viruses cause the majority of sore throats, including rhinovirus, coronavirus, adenovirus, influenza, parainfluenza, and respiratory syncytial virus 1
• Epstein-Barr virus (infectious mononucleosis) presents with pharyngitis plus generalized lymphadenopathy and splenomegaly—specifically look for posterior cervical adenopathy on exam 1
• Herpes simplex virus and coxsackievirus (herpangina) may cause characteristic vesicular lesions 2
• Viral pharyngitis is strongly suggested by: conjunctivitis, cough, hoarseness, coryza, diarrhea, anterior stomatitis, discrete ulcerative lesions, or viral exanthem 1

Bacterial Etiologies

• GABHS is the most common bacterial cause and the only one definitively requiring antibiotic therapy 2
• Clinical features suggesting GABHS: sudden-onset sore throat, fever, tonsillar exudates, tender anterior cervical adenopathy, absence of cough, and patient age 5-15 years 1
• Groups C and G β-hemolytic streptococci can cause pharyngitis with milder presentation than GABHS, though severe cases have been reported 1
• Mycoplasma pneumoniae and Chlamydia pneumoniae are uncommon causes, typically associated with atypical pneumonia 2
• Neisseria gonorrhoeae should be considered in sexually active individuals 2
• Arcanobacterium haemolyticum causes pharyngitis with scarlet fever-like rash, particularly in teenagers and young adults 2
• Corynebacterium diphtheriae is rare in Europe but presents with characteristic membrane 2

Critical Distinction: GABHS Carriers vs. Acute Infection

• Chronic GABHS carriers (10.9% in children ≤14 years, 2.3% in adults 15-44 years) with intercurrent viral infections are difficult to differentiate from acute infection 1
• Carriers show extremely low risk of post-streptococcal complications and low likelihood of transmission 1

Life-Threatening Complications

Suppurative Complications

• Peritonsillar abscess (quinsy) is polymicrobial, occurring mainly in young adults, presenting with severe unilateral throat pain, trismus, uvular deviation, and "hot potato voice" 1
• Lemierre's syndrome (suppurative thrombophlebitis of internal jugular vein) presents with persistent fever, neck pain, and septic emboli 1
• Acute epiglottitis is a medical emergency requiring immediate intubation and antibiotics for Haemophilus influenzae type b 3

Non-Suppurative Complications

• Acute rheumatic fever has very low incidence in developed countries; prevention depends on effective control of GABHS pharyngitis in high-risk patients (those with previous rheumatic fever or family history) 1
• Acute poststreptococcal glomerulonephritis follows GABHS pharyngitis after a latency period of a few weeks 1

Non-Infectious Causes

• Gastroesophageal reflux disease (GERD) can cause chronic throat irritation 1
• Allergic rhinitis with postnasal drip may present as chronic sore throat 1
• Chronic irritant exposure from smoking, environmental allergens, or occupational exposures 1
• Thyroiditis is a relatively uncommon consideration 4

Diagnostic Approach

Clinical Risk Stratification

Use the Centor criteria (1 point each): fever, absence of cough, tonsillar exudates, tender anterior cervical lymphadenopathy 2

• Score 0-2: Low probability of GABHS—do NOT test or prescribe antibiotics 2
• Score 3-4: Higher probability of GABHS—consider rapid antigen detection test (RADT) before prescribing antibiotics 2

Laboratory Testing

• Throat culture is NOT necessary for routine diagnosis of acute sore throat 2
• If RADT is performed, throat culture is not necessary after a negative RADT in both children and adults 2
• In patients with 3-4 Centor criteria, physicians can consider the use of RATs 2
• Biomarkers (CRP, procalcitonin) are not necessary to routinely use in assessment of acute sore throat 2

Common Pitfall

Clinical features alone cannot reliably distinguish GABHS from viral pharyngitis—microbiological confirmation is required when GABHS is suspected 1

Treatment Algorithm

Symptomatic Management (All Patients)

Either ibuprofen or paracetamol are strongly recommended for relief of acute sore throat symptoms 2

Antibiotic Decision-Making

For Centor Score 0-2:

• Do NOT prescribe antibiotics—the presentation is too mild and antibiotics provide no meaningful benefit 2, 5
• Provide symptomatic relief only 5

For Centor Score 3-4:

• Perform RADT before prescribing antibiotics 5
• Discuss modest benefits versus risks with the patient, including side effects, antimicrobial resistance, and costs 2, 5
• If antibiotics are indicated, penicillin V twice or three times daily for 10 days is recommended 2, 6
• For penicillin-allergic patients: first-generation cephalosporins, clindamycin, or macrolides can be used 1

What NOT to Use

• Zinc gluconate is not recommended for sore throat 2
• Herbal treatments and acupuncture have inconsistent evidence 2
• Corticosteroids are not routinely recommended, though can be considered in severe presentations (3-4 Centor criteria) in conjunction with antibiotics 2

Critical Evidence on Antibiotic Benefits

• Antibiotics should NOT be used in patients with 0-2 Centor criteria to relieve symptoms 2
• Modest benefits of antibiotics observed in patients with 3-4 Centor criteria must be weighed against side effects, effect on microbiota, increased antibacterial resistance, medicalization, and costs 2
• Prevention of suppurative complications is NOT a specific indication for antibiotic therapy in sore throat 2

Management of Chronic GABHS Carriers

• Antimicrobial therapy is NOT indicated for the large majority of chronic streptococcal carriers 1
• Eradication may be desirable in special situations: community outbreak of acute rheumatic fever/glomerulonephritis/invasive GAS, outbreak in closed community, family/personal history of acute rheumatic fever, excessive family anxiety, or when tonsillectomy is being considered only because of carriage 1
• For carrier eradication: use oral clindamycin 20-30 mg/kg/d in 3 doses for 10 days, penicillin V plus rifampin, amoxicillin-clavulanate, or benzathine penicillin G plus rifampin 1