The modified Duke criteria combine microbiological findings, evidence of endocardial involvement and minor clinical findings to classify endocarditis.
Major criteria
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Blood culture evidence includes a typical organism from two cultures, persistently positive cultures taken more than 12 hours apart, or three or more positive cultures taken over more than 1 hour.
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Endocardial involvement includes echocardiographic evidence of vegetations or new valvular regurgitation.
Minor criteria
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Predisposing valvular or cardiac abnormalities and intravenous drug misuse are minor criteria.
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Other minor criteria include pyrexia ≥38°C, embolic phenomena and vasculitic phenomena.
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Suggestive blood cultures that do not achieve major criteria and suggestive echocardiographic findings also count as minor criteria.
Diagnostic combinations
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Definite endocarditis requires two major criteria, one major plus three minor criteria, or five minor criteria.
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Possible endocarditis requires one major plus one minor criterion, or three minor criteria.