What are Duke's criteria for diagnosing infective endocarditis?

Duke Criteria for Infective Endocarditis

The Modified Duke Criteria stratify patients with suspected infective endocarditis into three diagnostic categories—definite, possible, or rejected—using a combination of major and minor clinical, microbiological, and echocardiographic criteria. 1

Diagnostic Categories

Definite Infective Endocarditis can be established through either:

Pathological Criteria

• Microorganisms demonstrated by culture or histological examination of a vegetation, embolized vegetation, or intracardiac abscess specimen 1
• Pathological lesions showing active endocarditis on histological examination of vegetation or intracardiac abscess 1

Clinical Criteria (any one of the following)

• 2 major criteria 1
• 1 major criterion AND 3 minor criteria 1
• 5 minor criteria 1

Possible Infective Endocarditis requires:

• 1 major criterion AND 1 minor criterion 1
• 3 minor criteria 1

Rejected Cases include:

• Firm alternative diagnosis explaining evidence of IE 1
• Resolution of IE syndrome with antibiotic therapy for ≤4 days 1
• No pathological evidence of IE at surgery or autopsy after antibiotic therapy for ≤4 days 1
• Does not meet criteria for possible IE 1

Major Criteria

Blood Culture Positive for IE

Typical microorganisms from 2 separate blood cultures:

• Viridans streptococci 1
• Streptococcus bovis 1
• HACEK group organisms 1
• Staphylococcus aureus (regardless of whether nosocomial or community-acquired, with or without removable focus) 1
• Community-acquired enterococci in the absence of a primary focus 1

Important modification: The original Duke criteria only considered S. aureus bacteremia a major criterion if community-acquired, but the modified criteria expanded this to include nosocomial S. aureus bacteremia because 13% of hospital-acquired S. aureus bacteremia cases were subsequently diagnosed with definite IE. 1

Persistently positive blood cultures:

• At least 2 positive cultures drawn >12 hours apart 1
• All of 3, or majority of ≥4 separate blood cultures (with first and last drawn at least 1 hour apart) 1

Single positive blood culture for Coxiella burnetii OR anti-phase I IgG antibody titer >1:800 1

This was upgraded from a minor to major criterion because serological testing proved highly specific for Q fever endocarditis. 1

Evidence of Endocardial Involvement

Positive echocardiogram (TEE recommended for prosthetic valves, complicated IE, or paravalvular abscess; TTE as first test in other patients) showing: 1

• Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant jets, or on implanted material without alternative anatomic explanation 1
• Abscess 1
• New partial dehiscence of prosthetic valve 1
• New valvular regurgitation (worsening or changing of preexisting murmur is NOT sufficient) 1

Minor Criteria

• Predisposition: Predisposing heart condition or injection drug use 1
• Fever: Temperature ≥38°C 1
• Vascular phenomena: Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, Janeway lesions 1
• Immunologic phenomena: Glomerulonephritis, Osler's nodes, Roth spots, rheumatoid factor 1
• Microbiological evidence: Positive blood culture that does not meet major criterion OR serological evidence of active infection with organism consistent with IE 1

Critical modification: Echocardiographic minor criteria were eliminated from the modified Duke criteria because transesophageal echocardiography became widely available, making vague echocardiographic findings less diagnostically useful. 1

Common Pitfalls and Clinical Caveats

Blood culture-negative endocarditis remains a major diagnostic challenge, occurring in approximately 10% of cases when cultures are properly obtained. 2 The most common cause is prior antibiotic administration before blood cultures are drawn. 3 In one study, 63% of patients had received antibiotics prior to blood culture, resulting in 71% blood culture-negative IE. 3

Right-sided endocarditis may not present with classic peripheral embolic or immunologic phenomena because valve lesions do not create the same peripheral manifestations as left-sided disease, though septic pulmonary emboli can occur. 1

Acute versus subacute presentation: Acute IE (often S. aureus) may evolve too quickly for immunologic vascular phenomena to develop, which are more characteristic of subacute disease. 1

Prosthetic valve endocarditis has lower diagnostic sensitivity with Duke criteria—only 50% were classified as definite by the original Duke criteria compared to 83% for native valve endocarditis. 4

The Duke criteria demonstrated 80% sensitivity and high specificity across diverse patient populations including adults, pediatrics, injection drug users, and patients with both native and prosthetic valves. 1 However, 24% of pathologically proven IE cases may still be misclassified as "possible IE," particularly in culture-negative cases and Q fever endocarditis. 5