Criteria

Classically, the Duke criteria have been used to help classify a diagnosis of IE; there have been several iterations of these since they were first developed in 1994. The most widely used criteria now are the European Society of Cardiology diagnostic criteria, which were updated in 2023 and incorporate a multimodality imaging approach in addition to the existing Duke criteria for diagnosis.[7]

Duke criteria​​[48][49]

Major criteria:

  1. Positive blood culture for IE:

    • Typical micro-organism for IE from 2 separate blood cultures

    • Typical micro-organism for IE from persistently positive blood cultures; either:

      • ≥2 positive blood cultures of blood samples drawn >12 hours apart

        OR

      • All of 3 or a majority of ≥4 separate cultures of blood (with first and last samples drawn ≥1 hour apart

  2. Evidence of endocardial involvement:

    • Positive echocardiogram for IE:

      • Oscillating intracardiac mass on valve or on supporting structures, or in the path of regurgitant jets, or on implanted material in the absence of an alternative anatomical explanation

    • Abscess

    • New partial dehiscence of prosthetic valve

    • New valvular regurgitation

  3. Single positive blood culture for Coxiella burnetii or phase I IgG antibody titre >1:800.

Minor criteria:

  1. Predisposing heart condition or intravenous drug use

  2. Fever over 38°C (>100.4°F)

  3. Vascular phenomenon such as major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions

  4. Immunological phenomenon:

    • Glomerulonephritis

    • Osler nodes

    • Roth spots

    • Rheumatoid factor

  5. Microbiological evidence:

    • Positive blood cultures not meeting major criteria or serological evidence of active infection with organism consistent with IE.

These criteria are used to classify patients with suspected infective endocarditis as 'definite', 'possible', or 'rejected'.

  • Definite IE

    Must meet:

    • 2 major criteria

      OR

    • 1 major and 3 minor criteria

      OR

    • 5 minor criteria

      OR any one of the following pathological criteria:

      • Micro-organisms demonstrated by culture or on histological examination of a vegetation, a vegetation that has embolised, or an intracardiac abscess specimen

      • Pathological lesions; vegetation or intracardiac abscess confirmed by histological examination showing active endocarditis

  • Possible IE

    Must meet:

    • 1 major and 1 minor criteria

      OR

    • 3 minor criteria

  • Rejected IE

    Must meet any one of the following criteria:

    • Firm alternative diagnosis

    • Resolution of symptoms suggesting IE with antibiotic therapy for ≤4 days

    • No pathological evidence of IE at surgery or autopsy, with antibiotic therapy for ≤4 days

    • Does not meet criteria for possible IE (see above).

2023 European Society of Cardiology criteria for the diagnosis of infective endocarditis​[7]

Major criteria:

  1. Blood culture positive for IE

    • Typical microorganisms consistent with IE from two separate blood cultures: oral streptococci, Streptococcus gallolyticus (formerly S treptococcus bovis), HACEK group, Staphylococcus aureus, Enterococcus faecalis.

    • Microorganisms consistent with IE from continuously positive blood cultures:

      1. ≥2 positive blood cultures of blood samples drawn >12 hours apart

      2. All of 3 or a majority of ≥4 separate cultures of blood (with first and last samples drawn ≥1 hour apart).

    • Single positive blood culture for Coxiella burnetii or phase I IgG antibody titre >1:800.

  2. Imaging positive for IE

    • Valvular, perivalvular/periprosthetic, and foreign material anatomic and metabolic lesions characteristic of IE detected by any of the following imaging techniques:

      1. Echocardiography (transthoracic [TTE] and trans-oesophageal [TOE])

      2. Cardiac computed tomography (CT)

      3. 18F-FDG-positron emission tomography (PET)/CT (angiography)

      4. White blood cell single-photon emission CT (WBC SPECT)/CT.

Minor criteria:

  1. Predisposing conditions (i.e., predisposing heart condition at high or intermediate risk of IE or people who inject drugs)

  2. Fever defined as temperature >38°C (>100.4°F)

  3. Embolic vascular dissemination (including those asymptomatic detected by imaging only):

    • Major systemic and pulmonary emboli/infarcts and abscesses

    • Haematogenous osteoarticular septic complications (i.e., spondylodiscitis)

    • Mycotic aneurysms

    • Intracranial ischaemic/haemorrhagic lesions

    • Conjunctival haemorrhages

    • Janeway’s lesions.

  4. Immunological phenomena:

    • Glomerulonephritis

    • Osler nodes and Roth spots

    • Rheumatoid factor.

  5. Microbiological evidence:

    • Positive blood culture but does not meet a major criterion as noted above

    • Serological evidence of active infection with organism consistent with IE.

These criteria are used to classify patients with suspected infective endocarditis as 'definite', 'possible', or 'rejected'.

  • Definite IE

    Must meet:

    • 2 major criteria

    • 1 major criterion and at least 3 minor criteria

    • 5 minor criteria

  • Possible IE

    Must meet:

    • 1 major criterion and 1 or 2 minor criteria

    • 3-4 minor criteria

  • Rejected IE

    • Does not meet criteria for definite or possible at admission with or without a firm alternative diagnosis.

If the diagnosis of IE is classified as ‘possible’ or ‘rejected’ but there is still a high level of clinical suspicion:

  • Repeat blood cultures

  • Repeat echocardiography within 5-7 days

  • Perform cardiac CT angiography (CTA) to diagnosis valvular lesions

  • Consider other imaging modalities:

    • Brain or whole-body imaging (MRI, CT, PET/CT, or WBC SPECT) to detect distant lesions in suspected native valve IE

    • WBC SPECT and brain or whole-body imaging (MRI, CT, PET/CT, or WBC SPECT) to detect distant lesions in suspected prosthetic

    • PET/CT to detect pocket infection or pulmonary embolism in patients with cardiac device-related IE.

If the diagnosis of IE is confirmed ‘definite’, further imaging is still warranted:

  • Cardiac CTA if there are suspected paravalvular complications and TOE is inconclusive

  • Brain and whole-body imaging (CT, 18F-FDG-PET/CTA, and/or MRI) for all patients with confirmed IE, in particular if there are symptoms suggestive of extracardiac complications.

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