What are the Modified Duke criteria for infective endocarditis?

The modified Duke criteria for the clinical diagnosis of infective endocarditis:

The diagnosis of infective endocarditis is established with certainty only when vegetation is examined histologically and microbiologically. Nevertheless， a highly sensitive and specific diagnostic schema, known as the modified Duke criteria, based on clinical, laboratory and echocardiographic findings, is commonly encountered in patients with endocarditis. It has two types of criteria (see below).

A. Major criteria: 2 in numbers

1. Positive blood culture (3 ways)

a. Typical microorganism for infective endocarditis from two separate blood cultures (Viridans streptococci, Streptococcus gallacticus, HACEK group organisms, Staphylococcus aureus, or community-acquired enterococci in the absence of primary focus)

Or,

b. Persistently positive blood culture, defined as recovery of a microorganism consistent with infective endocarditis from;

• Blood cultures were drawn> 12 hours apart; or
• All of 3 or a majority of ≥4 separate blood cultures, with first and last drawn at least 1 hour apart.

Or,

c. Single positive blood culture for Coxiella burnetii (Q fever) or (with an immunofluorescence assay) phage 1 IgG antibody titer of >1: 800.

2. Evidence of endocardial involvement (2 ways)

1. Positive echocardiogram (3 types of findings)

• Oscillating intracardiac mass on valve or supporting structures or in the path of regurgitant jets or in implanted material, in the abscess of an alternative anatomical explanation, or
• Abscess, or
• New partial dehiscence of prosthetic valve.

Or

2.New valvular regurgitation (increased or change in preexisting murmur not sufficient)

 From Davidson's (fig no.16.89)

B. Minor criteria:

• Predisposition: predisposing heart conditions or injection drug use.
• Fever: ≥38.0°C (≥100.4°F).
• Vascular phenomena: Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions.
• Immunologic phenomena: Glomerulonephritis, Osler’s nodes, Roth’s spots, rheumatoid factor.
• Microbiological evidence: Positive blood culture but not meeting major criteria, as noted previously or, serological evidence of active infection with an organism consistent with infective endocarditis
• Echocardiogram: findings consistent with infective endocarditis but not meeting a major criterion as noted above

According to duke criteria: Definite endocarditis is defined by documentation of two major criteria or of one major and three minor criteria or of five minor criteria.

In a nutshell: The diagnosis of infective endocarditis is definite when:

• A microorganism is demonstrated by a culture of a specimen from vegetation, an embolism or an intracardiac abscess
• Active endocarditis is confirmed by histological examination of the vegetation or intracardiac abscess;
• Two major clinical criteria, one major and three minor criteria, or five minor criteria are met (This is modified Duke Criteria)

Source:

• Harrison’s Principles of Internal Medicine 2 volumes 19th Edition: 819 (1176)
• Davidsons Principles and Practice of Medicine 23 edition; 554(531)
• Kumar & Clark’s Clinical Medicine 9th Edition: 1019 (2514)