What is the differential diagnosis and appropriate evaluation and management for sore throat (pharyngitis) in an otherwise healthy adult or adolescent?

Differential Diagnosis of Throat Pain

Most throat pain is viral and does not require antibiotics; test only patients with clinical features suggesting Group A Streptococcus (fever, tonsillar exudates, tender anterior cervical adenopathy, absence of cough) and treat only those with confirmed positive testing. 1

Viral Causes (Most Common)

Viruses account for the majority of acute pharyngitis cases and require only symptomatic treatment 1, 2:

• Respiratory viruses: Adenovirus, parainfluenza, rhinovirus, respiratory syncytial virus 2, 3
• Enteroviruses: Coxsackievirus, echovirus 2, 4
• Herpes simplex virus 2, 3
• Epstein-Barr virus (EBV): Presents distinctively with generalized lymphadenopathy, splenomegaly, posterior cervical adenopathy, significant fatigue, and atypical lymphocytes 2, 3
• Influenza virus: Consider during seasonal outbreaks 4

Critical pitfall: Never prescribe amoxicillin or ampicillin if EBV/infectious mononucleosis is suspected—this causes severe maculopapular rash 3

Bacterial Causes

Group A Streptococcus (GAS) is the only common bacterial cause requiring antibiotic treatment to prevent acute rheumatic fever and suppurative complications 1, 2:

• Accounts for 15-30% of pharyngitis in children aged 5-15 years 2, 3
• Accounts for only 5-15% in adults 1, 3
• Clinical features: Sudden onset sore throat, fever, tonsillopharyngeal erythema ± exudates, tender enlarged anterior cervical nodes, absence of cough 2

Rare bacterial causes (generally do not require routine testing or treatment) 1, 3:

• Groups C and G β-hemolytic streptococci: Can cause pharyngitis but no rheumatic fever risk 1
• Fusobacterium necrophorum: Implicated in 10-20% of adolescent pharyngitis; can cause life-threatening Lemierre syndrome 1
• Neisseria gonorrhoeae: Consider in sexually active persons 1
• Arcanobacterium haemolyticum: May cause scarlatiniform rash in teenagers/young adults 1

Critical pitfall: Remain vigilant for Lemierre syndrome in adolescents and young adults with severe pharyngitis—urgent diagnosis and treatment is necessary to prevent complications and death 1, 3

Diagnostic Algorithm

Step 1: Apply Modified Centor Criteria 1, 3

Assign 1 point each for:

• Fever by history
• Tonsillar exudates
• Tender anterior cervical adenopathy
• Absence of cough

Interpretation:

• Score <3: Low probability of GAS—no testing needed, symptomatic treatment only 1, 3
• Score 3-4: Moderate probability—perform microbiological testing 1

Step 2: Testing Strategy (for Centor ≥3)

For children and adolescents 1, 3:

• Perform Rapid Antigen Detection Test (RADT) first
• If RADT positive → treat (no backup culture needed)
• If RADT negative → perform backup throat culture (due to lower RADT sensitivity and higher rheumatic fever risk)

For adults 1:

• Perform RADT
• If RADT positive → treat
• If RADT negative → no backup culture needed (due to low GAS prevalence, extremely low rheumatic fever risk, and high RADT specificity) 1

Do not test patients with obvious viral features: cough, rhinorrhea, conjunctivitis, hoarseness 3

Treatment

For Confirmed GAS Pharyngitis

First-line therapy (10-day course to prevent acute rheumatic fever) 1, 2, 4:

• Oral penicillin V, OR
• Oral amoxicillin (better palatability, equal efficacy), OR
• Intramuscular benzathine penicillin G (single dose)

Penicillin-allergic patients 2, 4:

• First-generation cephalosporins (cephalexin) for non-immediate hypersensitivity
• Azithromycin, erythromycin, or clindamycin for immediate hypersensitivity

For Viral Pharyngitis

Symptomatic treatment only 1, 4:

• Analgesics: Aspirin, acetaminophen, NSAIDs, throat lozenges 1
• Reassure patients that typical course is <1 week 1
• Antibiotics provide minimal benefit (NNT = 6 at 3 days, NNT = 21 at 1 week) and risk adverse effects 1

Key Clinical Pitfalls

• Over 60% of adults with sore throat receive unnecessary antibiotics—this drives antibiotic resistance 1, 3
• Do not treat chronic GAS carriers—they are at little/no risk for complications and unlikely to spread infection 1
• Laboratory confirmation is essential—physicians greatly overestimate the probability of GAS pharyngitis based on clinical features alone 1
• Watch for red flags requiring urgent evaluation: Difficulty swallowing, drooling, neck tenderness/swelling, severe pharyngitis in adolescents/young adults (peritonsillar abscess, parapharyngeal abscess, epiglottitis, Lemierre syndrome) 1