What are the Modified Duke criteria for diagnosing infective endocarditis?

Modified Duke Criteria for Diagnosing Infective Endocarditis

The Modified Duke Criteria classify infective endocarditis as definite, possible, or rejected based on specific pathological or clinical criteria, with definite IE requiring either pathological confirmation OR 2 major criteria, 1 major plus 3 minor criteria, or 5 minor criteria. 1

Definite Infective Endocarditis

Pathological Criteria

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

Clinical Criteria (Any of the Following)

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

Major Criteria

Blood Culture Positive for IE

Typical microorganisms from 2 separate blood cultures: 1, 2

• Viridans streptococci
• Streptococcus bovis (now Streptococcus gallolyticus)
• HACEK group organisms
• Staphylococcus aureus (regardless of whether nosocomial or community-acquired, with or without removable focus) 1, 3
• Community-acquired enterococci in the absence of a primary focus

Persistently positive blood cultures: 1, 2

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

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

Evidence of Endocardial Involvement on Echocardiography

• Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant jets, or on implanted material (without alternative anatomic explanation) 1, 2
• Abscess (perivalvular or myocardial) 1, 2
• New partial dehiscence of prosthetic valve 1, 2
• New valvular regurgitation (worsening or changing of preexisting murmur is NOT sufficient) 1, 2

Minor Criteria

• Predisposition: Predisposing heart condition or injection drug use 2, 4
• Fever: Temperature ≥38.0°C 2, 4
• Vascular phenomena: Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, Janeway lesions 2, 4
• Immunologic phenomena: Glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor 2, 4
• Microbiological evidence: Positive blood culture that does not meet major criterion, or serological evidence of active infection with organism consistent with IE 2, 4

Possible Infective Endocarditis

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

Rejected

• 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

Key Modifications from Original Duke Criteria

The most critical modification is that S. aureus bacteremia is now a major criterion regardless of whether it is nosocomial or community-acquired, because 13-46% of hospital-acquired S. aureus bacteremia cases develop definite IE. 1, 3

Q fever serology (anti-phase I IgG >1:800) or single positive blood culture for C. burnetii was upgraded from minor to major criterion after studies showed this reclassified culture-negative cases from possible to definite IE. 1, 3

Critical Diagnostic Approach

• Obtain at least 3 sets of blood cultures from separate venipuncture sites before initiating antibiotics, with first and last samples drawn at least 1 hour apart 5
• Perform transthoracic echocardiography (TTE) first in all suspected cases 1, 5
• Proceed immediately to transesophageal echocardiography (TEE) if TTE is negative but clinical suspicion remains high, prosthetic valve is present, intracardiac device leads are present, or optimal TTE windows cannot be obtained 5
• Repeat echocardiography 7-10 days later if initially negative but clinical suspicion remains high 5

Important Caveats

The Duke criteria are meant to guide diagnosis but must not replace clinical judgment—clinicians may appropriately decide to treat regardless of whether criteria are met or not met. 1, 5

The modified Duke criteria have approximately 80% sensitivity when evaluated at end of follow-up, but lower diagnostic accuracy for early diagnosis, particularly in prosthetic valve endocarditis and pacemaker/defibrillator lead IE 5, 2

Blood cultures are positive in approximately 90% of IE cases when properly obtained, with prior antibiotic administration being the most common cause of culture-negative IE 5

For culture-negative cases at 48 hours with persistent clinical suspicion, pursue specialized serological testing for Coxiella burnetii, Bartonella spp., Brucella spp., and other fastidious organisms 5