Diagnostic criteria for infective endocarditis

What it is

The modified Duke criteria help categorize the diagnostic likelihood of infective endocarditis: definite vs. possible. Definite IE if any one of three is met: 1. 2 major criteria; 2. 1 major criterion plus 3 minor criteria; 3. 5 minor criteria. Probable IE is 1 major and 1 minor, or 3 minor. A pathologic diagnosis is separate: a positive culture from the valve or from an embolized vegetation, or histology showing endocarditis. Be Timer holds them. The two major: 1. Blood culture positive; 2. Echocardiographic evidence of endocardial involvement. The five minor: 1. Temperature >38 C; 2. Immunological phenomena, Osler's nodes and Roth spots; 3. Microbiological evidence; 4. Embolic phenomenon; 5. Risk factors, a congenital heart condition or IV drug use.

How it is diagnosed

There are two major criteria.

1. Blood microbiological evidence, met by any one of three: first, typical organisms associated with endocarditis - viridans strep, S. aureus, bovis, HACEK, community-acquired enterococcus - from 2 separate blood cultures; second, an organism consistent with IE from blood cultures separated in time and space, that is 2 cultures separated 12 hours apart and from different locations, or 3 of 4 cultures positive with at least 1 hour between the first and the last; third, a positive Coxiella culture, or an antiphase I IgG titre >1:800 - antiphase I is specific for Q fever endocarditis, while antiphase II is specific for acute Q.
2. Endocardial involvement, met by echocardiographic evidence of an oscillating intracardiac mass with absence of an anatomic alternative, or a valvular abscess, or partial dehiscence of a prosthetic valve, or by new valvular regurgitation. A worsening or changing preexisting murmur is not sufficient.

TEE is recommended in three settings: 1. patients with prosthetic valves; 2. patients rated at least possible IE by clinical criteria; 3. complicated IE with a paravalvular abscess. TTE is the first test in other patients.