Centor/McIsaac Score
Clinical prediction rule to estimate strep throat probability and guide testing and antibiotic decisions.
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Score 0-1: Low risk, no testing Score 2-3: Test before treating Score 4-5: Empiric antibiotics reasonable
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Why: Reduces unnecessary antibiotics and guides appropriate testing for pharyngitis.
How: Four criteria (fever, no cough, exudates, lymphadenopathy) plus age adjustment. Score 0-5 maps to strep probability.
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🦠 Classic Strep Presentation
School-age child with classic Group A strep signs - high fever, exudates, adenopathy
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🤧 Likely Viral Pharyngitis
Adult with sore throat, cough, and runny nose - typical viral presentation
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❓ Uncertain Diagnosis
Young adult with some strep features but also cough present
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🔄 Recurrent Strep History
Patient with multiple previous strep infections presenting with symptoms
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👴 Elderly Patient
Older adult with sore throat - lower strep probability due to age
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Sample Clinical Scenarios
🦠 Classic Strep Presentation
School-age child with classic Group A strep signs - high fever, exudates, adenopathy
Click to load
🤧 Likely Viral Pharyngitis
Adult with sore throat, cough, and runny nose - typical viral presentation
Click to load
❓ Uncertain Diagnosis
Young adult with some strep features but also cough present
Click to load
🔄 Recurrent Strep History
Patient with multiple previous strep infections presenting with symptoms
Click to load
👴 Elderly Patient
Older adult with sore throat - lower strep probability due to age
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Centor/McIsaac Assessment
Core Centor Criteria (Each = 1 point)
Patient Information
Additional Factors
Centor Score Results
McIsaac Score
Original: 0/4
Strep Probability
Testing
Antibiotics
Very Low Risk
No testing or antibiotics needed. Symptomatic treatment only.
Score Analysis
Score Breakdown
Probability by Score
Recommended Actions
Symptomatic treatment recommended (rest, fluids, analgesics)
No strep testing necessary
Antibiotics not indicated
Differential Diagnosis
Viral pharyngitis (most likely)
Adenovirus infection
Rhinovirus/coronavirus
Group A Streptococcus (GAS)
Infectious mononucleosis
Fusobacterium necrophorum
Calculation Steps
Fever >38°C (100.4°F): 0
Absence of cough: 0
Tonsillar swelling/exudates: 0
Tender anterior cervical lymphadenopathy: 0
Original Centor Score: 0/4
Patient age: 25 years
Age 15-44 years: 0 points (no change)
Modified McIsaac Score: 0 +0 = 0/5
Risk Category: Very Low Risk
Estimated GAS probability: 2.5%
Recommendation: No testing or antibiotics needed. Symptomatic treatment only.
For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
🏥 Health Facts
Validated in multiple studies
— Evidence-based
Supports antibiotic stewardship
— Clinical guidelines
What is the Centor Score?
The Centor Score is a clinical prediction rule used to estimate the probability that pharyngitis (sore throat) is caused by Group A Streptococcus (GAS). The Modified Centor Score, also known as the McIsaac Score, adds an age adjustment to improve accuracy. This tool helps clinicians decide whether to test for strep and/or prescribe antibiotics.
Strep Detection
Helps identify patients most likely to have bacterial vs viral pharyngitis, guiding appropriate care.
Antibiotic Stewardship
Reduces unnecessary antibiotic prescriptions by identifying low-risk patients who don't need treatment.
Evidence-Based
Validated in multiple studies with known probability ranges for each score level.
How Does the Centor Score Work?
Four Core Criteria
1. Fever
Temperature >38°C (100.4°F) - history or measured
2. Absence of Cough
Cough suggests viral cause; absence increases strep likelihood
3. Tonsillar Exudates
White/yellow patches on tonsils with swelling
4. Lymphadenopathy
Tender, swollen anterior cervical lymph nodes
When to Use the Centor Score
✅ Appropriate Use
- • Acute pharyngitis (sore throat)
- • Age 3 years and older
- • Primary care/urgent care settings
- • Deciding on strep testing
❌ Not Appropriate For
- • Children under 3 years
- • Peritonsillar abscess suspected
- • Chronic/recurrent pharyngitis
- • Immunocompromised patients (use lower threshold)
Score Calculation and Interpretation
Centor Score Formula
Range: 0-4 points
McIsaac Age Modification
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