What are the diagnostic criteria and treatment options for a patient presenting with a sore throat, considering the Centor criteria (Centor score) and potential penicillin allergy?

Centor Criteria for Sore Throat: Diagnostic and Treatment Algorithm

What Are the Centor Criteria?

The Centor criteria are a clinical scoring system consisting of four elements: fever by history, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of cough—used to stratify the likelihood of Group A Streptococcus (GAS) pharyngitis and guide testing decisions. 1

The four criteria are:

• Fever (by history)
• Tonsillar exudates (or pharyngeal exudates)
• Tender anterior cervical lymphadenopathy
• Absence of cough 2, 3

Each criterion present equals 1 point, for a maximum score of 4 1.

Risk Stratification and Testing Algorithm

Patients with fewer than 2 Centor criteria should NOT be tested or treated with antibiotics, as viral etiology is most likely. 1, 2

Score-Based Management:

• 0-1 criteria: No testing needed; viral pharyngitis is most likely. Provide symptomatic treatment only with ibuprofen or acetaminophen. 2, 4

• 2 criteria: Consider testing with rapid antigen detection test (RADT) or throat culture. Only treat if test is positive. 2, 3

• 3-4 criteria: Perform RADT or throat culture before prescribing antibiotics. These patients have higher likelihood of GAS infection but still require microbiological confirmation. 1, 2, 3

A critical pitfall: Do NOT prescribe antibiotics based on clinical features alone without microbiological confirmation, as clinical features cannot reliably distinguish GAS from viral pharyngitis. 2

Testing Approach

RADT is the preferred initial test and does NOT require confirmatory throat culture after a negative result in adults or children. 2

• Throat culture is not necessary for routine diagnosis but can be used as an alternative to RADT 1, 2
• Do NOT routinely use biomarkers such as C-reactive protein or procalcitonin 1, 2
• Throat cultures may be reserved for outbreak investigations or monitoring antibiotic resistance 3

Avoid testing patients with clear viral symptoms (cough, rhinorrhea, conjunctivitis, hoarseness, diarrhea, or oropharyngeal ulcers/vesicles), as this leads to false-positive results in asymptomatic carriers and unnecessary antibiotic use. 1, 2

Treatment for Confirmed GAS Pharyngitis

First-Line Antibiotic:

If antibiotics are indicated based on positive testing, penicillin V twice or three times daily for 10 days is the first-choice treatment. 1, 3

The evidence shows penicillin treatment for 7 days is superior to 3 days or placebo in resolving symptoms, with symptoms resolving approximately 1.9 days earlier 5. However, guidelines consistently recommend 10 days to ensure eradication of GAS from the pharynx 1.

For Penicillin-Allergic Patients:

In patients with penicillin allergy, use first-generation cephalosporins, clindamycin, or macrolide antibiotics (such as azithromycin or erythromycin). 6, 3

• Azithromycin has been shown to be clinically and microbiologically superior to penicillin V in some studies, with 95% bacteriologic eradication at Day 14 versus 73% for penicillin 7
• Important caveat: Approximately 1% of azithromycin-susceptible S. pyogenes isolates become resistant following therapy 7
• Erythromycin is an alternative macrolide option 3, 8

Warning for penicillin-allergic patients: Individuals with a history of penicillin hypersensitivity may experience severe reactions when treated with cephalosporins; careful inquiry about previous hypersensitivity reactions is mandatory. 9

Symptomatic Management

All patients with pharyngitis should receive symptomatic treatment with ibuprofen or acetaminophen, regardless of whether antibiotics are prescribed. 10, 4

• Ibuprofen is slightly more effective than acetaminophen for pain relief, particularly after 2 hours of administration 10
• Both medications are safe for short-term use with low risk of adverse effects 10
• Medicated throat lozenges used every two hours are also effective 6

Corticosteroids:

Corticosteroids are NOT routinely recommended but can be considered in adult patients with severe presentations (3-4 Centor criteria) when used in conjunction with antibiotic therapy. 1, 10

• Use single low-dose oral dexamethasone (maximum 10 mg) 10
• Corticosteroids provide only a small reduction in symptom duration and should not be used routinely 6
• Do NOT use corticosteroids in patients with 0-2 Centor criteria 10

Red Flags Requiring Urgent Evaluation

Immediately evaluate for life-threatening conditions if the patient presents with difficulty swallowing, drooling, neck tenderness, or neck swelling. 1, 2

These symptoms suggest:

• Peritonsillar abscess (quinsy): severe unilateral throat pain with trismus and uvular deviation 2
• Parapharyngeal abscess 1, 2
• Epiglottitis 1, 2
• Lemierre syndrome: persistent fever with neck pain in adolescents/young adults with severe pharyngitis, representing suppurative thrombophlebitis of the internal jugular vein 1, 2

Fusobacterium necrophorum is implicated in approximately 10-20% of endemic pharyngitis cases in adolescents and can cause Lemierre syndrome, a rare but life-threatening condition requiring urgent diagnosis and treatment 1.

Benefits and Limitations of Antibiotic Treatment

The benefit of antibiotics is modest: they shorten the duration of sore throat by only 1-2 days, with a number needed to treat of 6 at day 3 and 21 at one week. 1

What Antibiotics DO:

• Reduce symptom duration by approximately 1.9 days in GAS-positive patients 5
• May prevent complications including acute rheumatic fever (more common in children/adolescents), peritonsillar abscess, and further spread of GAS in outbreaks 1

What Antibiotics DO NOT Do:

• Do NOT routinely prescribe antibiotics to prevent rheumatic fever or acute glomerulonephritis in low-risk patients (those without previous history of rheumatic fever), as the absolute risk is extremely small 1, 4
• Little evidence supports prevention of acute glomerulonephritis 1
• Prevention of suppurative complications (quinsy, acute otitis media, cervical lymphadenitis, mastoiditis, acute sinusitis) is NOT a specific indication for antibiotic therapy 1

Common Pitfalls to Avoid

1. Do NOT prescribe antibiotics for patients with 0-2 Centor criteria, as antibiotics provide no meaningful benefit and the likelihood of bacterial infection is low 1, 4

2. Do NOT test or treat patients with viral symptoms (cough, nasal congestion, conjunctivitis, hoarseness, diarrhea, oropharyngeal lesions), as this leads to unnecessary antibiotic use in asymptomatic carriers 1, 2

3. Do NOT prescribe antibiotics without microbiological confirmation in patients with 2-3 Centor criteria 2, 3

4. Maintain high suspicion for life-threatening complications in patients with unusually severe presentations, particularly adolescents and young adults 2

5. Delayed antibiotic prescribing is a valid evidence-based strategy that reduces antibiotic use without increasing complication rates in patients with 3-4 Centor criteria 4