What are the Duke Criteria for Infective Endocarditis (IE) and how are they used in diagnosis and treatment?

Duke Criteria for Infective Endocarditis

Diagnostic Classification System

The Modified Duke Criteria stratify patients with suspected IE into three categories: definite IE (diagnosed by pathological or clinical criteria), possible IE, or rejected IE, and remain the universally accepted diagnostic standard. 1

Definite IE Requires Either:

Pathological Criteria:

• Microorganisms demonstrated by culture or histological examination of a vegetation, embolized vegetation, or intracardiac abscess specimen 1, 2
• Pathological lesions showing active endocarditis on histological examination 1

Clinical Criteria (any one of):

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

Possible IE Requires:

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

Rejected IE Includes:

• 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 with antibiotic therapy for ≤4 days 1
• Does not meet criteria for possible IE 1

Major Criteria

Microbiological Major Criteria:

Typical microorganisms from ≥2 separate blood cultures:

• Viridans streptococci 1, 2, 3
• Streptococcus bovis 1, 2, 3
• HACEK group organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) 1, 2, 3
• Staphylococcus aureus (regardless of whether hospital-acquired or community-acquired, with or without removable focus) 1, 3
• Community-acquired enterococci in the absence of a primary focus 1, 2, 3

Persistently positive blood cultures:

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

Culture-negative IE serological criteria:

• Single positive blood culture for Coxiella burnetii OR anti-phase I IgG antibody titer >1:800 1, 2, 3

Echocardiographic Major Criteria:

Positive echocardiogram showing:

• Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant jets, or on implanted material 1, 2, 3
• Abscess (periannular or intracardiac) 1, 2, 3
• New partial dehiscence of prosthetic valve 1, 2, 3
• New valvular regurgitation (worsening or changing of preexisting murmur is NOT sufficient) 1, 2, 3

Minor Criteria

Predisposition:

• Predisposing heart condition (mitral valve prolapse, prior IE, bicuspid aortic valve, valve stenosis/insufficiency) 2, 3, 4
• Injection drug use 1, 2, 3

Fever:

• Temperature ≥38.0°C 2, 3, 4

Vascular phenomena:

• Major arterial emboli 2, 3, 4
• Septic pulmonary infarcts 2, 3, 4
• Mycotic aneurysm 2, 3, 4
• Intracranial hemorrhage 2, 3, 4
• Conjunctival hemorrhages 2, 3, 4
• Janeway lesions 2, 3, 4

Immunologic phenomena:

• Glomerulonephritis 2, 3, 4
• Osler nodes 2, 3, 4
• Roth spots 2, 3, 4
• Rheumatoid factor 2, 3, 4

Microbiological evidence:

• Positive blood culture not meeting major criterion 2, 3, 4
• Serological evidence of active infection with organism consistent with IE 2, 3, 4

Diagnostic Performance

The Modified Duke Criteria demonstrate 80% sensitivity and high specificity across diverse patient populations, including adults, pediatrics, injection drug users, and patients with both native and prosthetic valves. 2 The criteria show superior diagnostic accuracy compared to older von Reyn criteria, particularly in right-sided IE, culture-negative IE, and S. aureus or viridans streptococcal bacteremias 5

Critical Modifications from Original Duke Criteria

The most important modification is that S. aureus bacteremia now qualifies as a major criterion regardless of acquisition source (nosocomial or community-acquired) and regardless of whether a removable focus exists. 1 This change reflects contemporary data showing that 45.8% of S. aureus IE cases are nosocomial, and 13% of hospital-acquired S. aureus bacteremia patients develop definite IE 1

Specific serological criteria for culture-negative IE pathogens (particularly C. burnetii causing Q fever) were elevated from minor to major criteria because studies showed this reclassified cases from possible to definite IE with improved diagnostic accuracy 1

Application in Clinical Practice

Blood Culture Technique:

Obtain ≥3 blood culture sets from separate venipunctures BEFORE starting antibiotics to avoid culture-negative endocarditis. 3 For severely ill patients, perform 3 separate venipunctures over 1-2 hours before initiating empirical therapy 4 For non-acutely ill patients with negative cultures, withhold antibiotics for ≥48 hours to improve diagnostic yield 4

Echocardiography Strategy:

Transthoracic echocardiography (TTE) should be the first test in most patients, but transesophageal echocardiography (TEE) is recommended for prosthetic valves or complicated IE. 4 Among clinically definite cases, 41% had vegetations defined only by TEE, highlighting its critical diagnostic role 5

Right-Sided IE Considerations:

Right-sided IE may present without classic peripheral stigmata because valve lesions do not create the peripheral emboli and immunologic vascular phenomena seen in left-sided disease, though septic pulmonary emboli occur. 1 The Duke Criteria perform significantly better than older criteria in diagnosing right-sided IE 5

Common Pitfalls and How to Avoid Them

Premature antibiotic administration is the leading cause of culture-negative endocarditis and diagnostic failure. 3 In one study, 63% of patients received antibiotics prior to blood culture, resulting in 71% culture-negative IE 6

Underestimating nosocomial S. aureus bacteremia leads to missed diagnoses—any S. aureus bacteremia should trigger consideration of IE. 3 The modification recognizing all S. aureus bacteremia as a major criterion addresses this pitfall 1

The "possible IE" category remains problematic, with 24% of pathologically proven IE cases misclassified as possible IE, particularly in culture-negative and Q-fever cases. 7 When Duke Criteria yield "possible IE" in patients with prior antibiotic therapy and typical echocardiographic findings, strongly consider treating as definite IE 7

Echocardiographic findings become more apparent with longer hospitalization—sensitivity of cardiac imaging increases from 29.5% at admission to 77.5% at discharge. 8 Do not reject IE based on initial negative echocardiography; repeat imaging if clinical suspicion remains high 8

For suspected culture-negative IE, consult microbiology or infectious disease specialists for guidance on molecular pathogen identification and serological testing for fastidious organisms. 4