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

Differential Diagnosis for Fever, Sore Throat, and Tachycardia

The differential diagnosis includes Group A Streptococcal (GAS) pharyngitis, viral pharyngitis (most common), infectious mononucleosis, and life-threatening conditions including epiglottitis, peritonsillar abscess, retropharyngeal abscess, Lemierre's syndrome, and Ludwig's angina that require immediate recognition. 1

Primary Differential Considerations

Group A Streptococcal Pharyngitis

• Sudden-onset severe sore throat, fever (typically 101-104°F), pain on swallowing, tender enlarged anterior cervical lymph nodes, tonsillopharyngeal erythema with or without exudates, soft palate petechiae, and beefy red swollen uvula 2
• Most common in children 5-15 years old, occurring in winter/early spring 2
• Absence of cough, coryza, hoarseness, conjunctivitis, or diarrhea supports bacterial rather than viral etiology 2, 3
• Accounts for only 15-30% of pediatric pharyngitis and 5-15% in adults 4

Viral Pharyngitis (Most Common)

• Presence of conjunctivitis, coryza, hoarseness, cough, or diarrhea strongly suggests viral origin 2, 3
• Caused by adenovirus, parainfluenza, rhinovirus, respiratory syncytial virus, Epstein-Barr virus, coxsackievirus, herpes simplex virus 2
• If viral features are present, testing for GAS should not be performed 3

Infectious Mononucleosis (Epstein-Barr Virus)

• Acute pharyngitis with generalized lymphadenopathy and splenomegaly 2
• Particularly common in adolescents and young adults 1

Life-Threatening Conditions Requiring Immediate Recognition

Epiglottitis

• Presents with fever, sore throat, drooling, stridor, and respiratory distress 1
• Medical emergency requiring immediate airway management 1

Peritonsillar Abscess

• Severe unilateral throat pain, trismus, muffled "hot potato" voice, uvular deviation 1
• Requires drainage and antibiotics 1

Retropharyngeal Abscess

• Fever, dysphagia, neck stiffness, respiratory distress 1
• More common in young children 1

Lemierre's Syndrome

• Internal jugular vein thrombophlebitis following pharyngitis, with septic emboli 1
• High mortality if untreated 1

Ludwig's Angina

• Rapidly progressive cellulitis of submandibular space with airway compromise 1
• Requires aggressive airway management and antibiotics 1

Other Bacterial Causes

• Groups C and G β-hemolytic streptococci (do not cause rheumatic fever) 2
• Arcanobacterium haemolyticum - causes pharyngitis with scarlatiniform rash in teenagers/young adults 2, 3
• Neisseria gonorrhoeae in sexually active individuals 2
• Corynebacterium diphtheriae (rare) 2

Diagnostic Approach

Clinical findings alone cannot reliably differentiate GAS from viral pharyngitis—microbiological confirmation is mandatory 2, 5, 3

Testing Strategy

• Perform throat culture or rapid antigen detection test (RADT) when clinical/epidemiological findings suggest GAS pharyngitis 2
• In children and adolescents: negative RADT must be confirmed with throat culture 2, 3
• In adults: negative RADT alone is sufficient without culture backup 2, 3
• Do not test if viral features (cough, rhinorrhea, conjunctivitis) are present—pretest probability too low 2, 3

Clinical Scoring

• Modified Centor or FeverPAIN scores help determine who needs testing 4, 6
• Score of 2-3 warrants RADT or throat culture 4

Treatment Based on Diagnosis

For Confirmed GAS Pharyngitis

First-line: Penicillin or amoxicillin for 10 days (narrow spectrum, proven efficacy, low cost) 2, 3

• Intramuscular benzathine penicillin G if compliance concerns 2

Penicillin-allergic patients:

• First-generation cephalosporin (if no immediate hypersensitivity) 2, 3
• Clindamycin, clarithromycin, or azithromycin 3

Critical Pitfalls to Avoid

• Never diagnose or treat based on clinical findings alone—this leads to massive antibiotic overuse 5
• Fever is not specific for bacterial pharyngitis and should never be used alone to decide on antibiotics 5
• Clinical impression alone predicts positive cultures only 80% of the time at best 5
• The classic triad of fever, exudates, and adenopathy is present in only 15% of GAS cases 7
• Tachycardia may simply reflect fever and does not distinguish bacterial from viral etiology 2

Complications if Untreated

• Acute rheumatic fever (rare in developed countries, extremely rare in adults) 2, 3
• Post-streptococcal glomerulonephritis 3
• Suppurative complications: peritonsillar abscess, cervical lymphadenitis 1