🦠 Duke’s criteria help classify suspected infective endocarditis as definite, possible or rejected. They combine microbiology, imaging, clinical features and predisposing risk factors. Do not use them in isolation - if clinical suspicion is high, discuss urgently with cardiology, microbiology and the endocarditis team.

ESC 2023 guidance states that at least three blood culture sets should be obtained at 30-minute intervals before antibiotics, using peripheral venepuncture and careful sterile technique. Some UK local antimicrobial guidance adds a useful practical distinction: if clinically stable, take at least three sets before antibiotics, preferably more spaced out when feasible; if septic, take three sets at 30-minute intervals so antibiotics are not delayed

📊 Major & Minor Criteria

Category	Criterion	Examples / Notes
Major	🦠 Positive blood cultures for typical organisms	Typical organisms include viridans streptococci, Staphylococcus aureus, Enterococcus faecalis, HACEK organisms and other organisms depending on valve/prosthetic context.
Major	🖥 Evidence of endocardial involvement	Echo evidence of vegetation, abscess, pseudoaneurysm, intracardiac fistula, valve perforation, aneurysm, or new partial dehiscence of a prosthetic valve.
Major	💔 New valvular regurgitation	New regurgitant murmur or imaging evidence. Worsening of a pre-existing murmur alone is not enough.
Major	🔬 Pathological or surgical evidence	Microorganisms or active endocarditis demonstrated from vegetation, embolus, abscess or surgical/intraoperative inspection.
Minor	🫀 Predisposition	Previous infective endocarditis, prosthetic valve, known valve disease, congenital heart disease, cardiac implantable electronic device, transcatheter valve, or injection drug use.
Minor	🌡 Fever	Temperature ≥38°C.
Minor	🩸 Vascular phenomena	Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhages, Janeway lesions.
Minor	🧬 Immunological phenomena	Glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor.
Minor	🧫 Microbiological evidence not meeting major criterion	Positive blood cultures or serology that support IE but do not fulfil a major microbiological criterion.
Minor	🧪 Supporting imaging or physical signs	Some updated criteria include additional imaging or examination findings that support IE but do not meet major criteria.

✅ Diagnostic Classification

Classification	Criteria
Definite infective endocarditis	2 major criteria OR 1 major + 3 minor criteria OR 5 minor criteria OR pathological evidence of infective endocarditis
Possible infective endocarditis	1 major + 1 minor criterion OR 3 minor criteria
Rejected infective endocarditis	Firm alternative diagnosis OR resolution with short-course antibiotics and no evidence of IE OR no pathological evidence at surgery/autopsy after short antibiotic exposure OR criteria for possible/definite IE not met

📝 Exam Pearls

🦠 Blood cultures + echo are the backbone of diagnosis.
🫀 Staphylococcus aureus bacteraemia should always make you think about endocarditis.
💔 New regurgitation is more important than a changing old murmur.
🩸 Janeway lesions are painless vascular lesions; Osler nodes are painful immunological lesions.
👁 Roth spots and glomerulonephritis are immunological phenomena.
🧫 Take blood cultures before antibiotics unless the patient is septic and treatment cannot wait.

🧠 Teaching Note

🫀 Infective endocarditis is difficult because it behaves like both an infection and an embolic/immunological disease. The vegetation is a mixture of platelets, fibrin and microorganisms, which explains persistent bacteraemia and embolic complications. The immune system then generates phenomena such as glomerulonephritis, Roth spots and Osler nodes. That is why Duke’s criteria combine microbiology, imaging, embolic signs, immune signs and risk factors rather than relying on one feature alone.

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Duke’s Criteria for Infective Endocarditis ✅

🫀 Duke’s Criteria for Infective Endocarditis

📊 Major & Minor Criteria

✅ Diagnostic Classification

📝 Exam Pearls

🧠 Teaching Note

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