Duke Criteria Calculator

Modified Duke Criteria for the diagnosis of infective endocarditis (IE). Combines major and minor clinical criteria to classify patients as definite, possible, or rejected IE.

Important Clinical Disclaimer: The Duke Criteria Calculator is intended for use by qualified healthcare professionals only. It is for educational and informational purposes and should not replace clinical judgement. Always interpret results alongside the full clinical picture and follow your local guidelines and protocols.
Major Criteria
Blood Culture Criteria

Select ONE of the following if applicable:

Evidence of Endocardial Involvement

Select ONE of the following if applicable:

Minor Criteria
Pathological Criteria (Definitive)

If present, these confirm definite IE regardless of other criteria:

Duke Classification Rules
Definite IE
  • Pathological criteria present, OR
  • 2 major criteria, OR
  • 1 major + 3 minor criteria, OR
  • 5 minor criteria
Possible IE
  • 1 major + 1-2 minor criteria, OR
  • 3-4 minor criteria
Rejected
  • Firm alternative diagnosis, OR
  • Resolution with ≤4 days antibiotics, OR
  • No pathological evidence at surgery/autopsy with ≤4 days antibiotics, OR
  • Does not meet criteria for possible IE
HACEK Organisms

Fastidious gram-negative bacteria associated with endocarditis:

  • Haemophilus species
  • Aggregibacter (formerly Actinobacillus)
  • Cardiobacterium hominis
  • Eikenella corrodens
  • Kingella species
Clinical Signs Guide
Janeway Lesions

Non-tender, erythematous, haemorrhagic macules on palms/soles (septic emboli)

Osler Nodes

Painful, raised lesions on fingers/toes (immune complex deposition)

Roth Spots

Retinal haemorrhages with pale centres on fundoscopy

Splinter Haemorrhages

Linear, red-brown streaks under nails (non-specific but suggestive)

Understanding the Duke Criteria

History and Development

The Duke Criteria were originally proposed by Durack et al. at Duke University in 1994, replacing the earlier Von Reyn criteria. Key updates include:

  • 2000 (Modified Duke): Added S. aureus bacteraemia as major criterion, refined minor criteria
  • 2015 (ESC Guidelines): Added PET/CT and cardiac CT imaging criteria
  • 2023 (ESC Update): Further emphasis on multimodality imaging

The criteria have sensitivity of approximately 80% and specificity of around 98% for native valve endocarditis.

When to Use Duke Criteria

Consider applying Duke Criteria when patients present with:

  • Fever with new or changing heart murmur
  • Fever with embolic phenomena (stroke, splenic infarcts)
  • Persistent bacteraemia (especially S. aureus, streptococci)
  • Prosthetic valve or cardiac device with fever
  • Injection drug use with fever
  • Fever with recent dental/invasive procedure
  • New heart failure with fever

Imaging in Infective Endocarditis

Modality Sensitivity Key Findings When to Use
TTE 50-70% (native valve)
50% (prosthetic)		 Vegetations, regurgitation, abscess First-line investigation in all suspected IE
TOE 90-100% (native)
85-95% (prosthetic)		 Small vegetations, perivalvular complications, prosthetic valve abnormalities Negative TTE with high suspicion, prosthetic valves, suspected complications
Cardiac CT High for anatomical detail Pseudoaneurysm, abscess, fistula, coronary involvement Pre-surgical planning, perivalvular complications, coronary assessment
PET/CT 73-97% (prosthetic valves) Increased FDG uptake around prosthetic material Prosthetic valve IE (>3 months post-op), embolic event detection
MRI Brain High for CNS involvement Embolic infarcts, mycotic aneurysms, haemorrhage Neurological symptoms, pre-surgical assessment

Frequently Asked Questions

Yes, but it's more challenging. Culture-negative endocarditis (CNE) occurs in 2.5-31% of cases, often due to:

  • Prior antibiotic therapy (most common cause)
  • Fastidious organisms (HACEK, nutritionally variant streptococci)
  • Intracellular pathogens (Coxiella, Bartonella, Tropheryma)
  • Fungi (especially in immunocompromised)
  • Non-infectious causes (marantic endocarditis, Libman-Sacks)

Request specific serologies (Coxiella, Bartonella, Brucella, Legionella), extended blood culture incubation, and molecular testing (16S rRNA PCR) on blood or tissue.

A negative TTE does not exclude IE, especially:

  • In prosthetic valve endocarditis (TTE sensitivity ~50%)
  • With small vegetations (<5mm)
  • In right-sided endocarditis
  • With perivalvular complications

Proceed to TOE, which has sensitivity 90-100% for native valve IE. If TOE is also negative but suspicion remains, consider:

  • Repeat TOE in 7-10 days
  • PET/CT (especially prosthetic valves)
  • Cardiac CT for anatomical complications

"Possible IE" is not a diagnosis to ignore - it means IE cannot be confirmed or excluded with current evidence. Management should include:

  • Continued clinical surveillance
  • Repeat blood cultures
  • Consider repeat/advanced imaging (TOE if only TTE done, PET/CT)
  • Extended serological testing
  • Empirical antibiotic therapy if clinical concern is high
  • Involvement of infectious diseases and cardiology

Treatment decisions should be made by the endocarditis team based on overall clinical assessment, not solely on Duke classification.

Duke Criteria have reduced sensitivity (around 70%) for prosthetic valve endocarditis (PVE) because:

  • TTE has lower sensitivity for prosthetic valves
  • Vegetations may be smaller or obscured by shadowing
  • Perivalvular complications are more common but harder to visualise

For PVE, the 2015 ESC guidelines recommend:

  • Early TOE in all suspected cases
  • PET/CT if prosthesis implanted >3 months (accounts for post-operative inflammation)
  • Cardiac CT for perivalvular complications
  • Lower threshold for "possible IE" to trigger full investigation

The following organisms in blood cultures should trigger IE investigation regardless of apparent source:

  • Staphylococcus aureus: Always perform echocardiography (TOE preferred)
  • Viridans group streptococci: High specificity for IE
  • Streptococcus gallolyticus (bovis): IE workup + colonoscopy (colorectal cancer association)
  • Enterococcus faecalis: Without obvious urinary/GI source
  • HACEK organisms: Almost pathognomonic for IE
  • Cutibacterium acnes: If prosthetic material present

Coagulase-negative staphylococci are usually contaminants but relevant in prosthetic valve/device patients.

Disclaimer

This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

  • Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.
  • Never disregard professional medical advice or delay seeking it because of information from this tool.
  • Clinical decision-making should always incorporate the full clinical context, patient preferences, and local protocols.
  • The creators of this tool accept no liability for decisions made based on its output.

If you are a patient: please discuss any results with your healthcare provider. This tool is designed for use by medical professionals and may not be appropriate for self-assessment.

References

  1. Durack DT, et al. New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Am J Med. 1994;96(3):200-209.
  2. Li JS, et al. Proposed modifications to the Duke criteria for the diagnosis of infective endocarditis. Clin Infect Dis. 2000;30(4):633-638. doi:10.1086/313753
  3. Habib G, et al. 2015 ESC Guidelines for the management of infective endocarditis. Eur Heart J. 2015;36(44):3075-3128. doi:10.1093/eurheartj/ehv319
  4. Delgado V, et al. 2023 ESC Guidelines for the management of endocarditis. Eur Heart J. 2023;44(39):3948-4042.
  5. NICE. Antimicrobial prescribing: endocarditis (NG190). 2023. https://www.nice.org.uk/guidance/ng190
  6. Baddour LM, et al. Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications. Circulation. 2015;132(15):1435-1486.