Diagnosis of endocarditis is based on blood cultures and echocardiographic findings [3].
Duke criteria are frequently used to confirm or rule out endocarditis and involve use of laboratory and echocardiographic evidence.
Diagnostic criteria
- Definite: 2 major, or 1 major and 3 minor, or 5 minor criteria
- Possible: 1 major and 1 minor, or 3 minor criteria
- Rejected: None of the criteria, or full resolution of symptoms with antibiotics in 4 days, or firm alternate diagnosis
Major criteria
1. Positive blood cultures
- Typical microorganisms from two separate cultures (Strep, Staph, HACEK, enterococci)
- Persistently positive blood cultures, taken at least twelve hours apart, or three or more positive cultures taken at least one hour apart
- Single positive culture for Coxiella burnetti or phase 1 IgG tire >1:800
2. Evidence of endocardial involvement
- Positive Echocardiogram: Oscillating intra-cardiac mass, Abscess or new partial valvular dehiscence
- New valvular regurgitation
Minor criteria
- Predisposition: Predisposing heart condition or injectable drug use
- Fever ≥ 38.0 C
- Vascular Phenomena: Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions
- Immunologic phenomenon: glomerulonephritis, Osler’s nodes, Roth’s spots, rheumatoid factor
- Microbiologic evidence: single positive blood culture, serologic evidence of infection with organism consistent with infective endocarditis
Learning Bite
Blood cultures and echocardiography are bedrocks of diagnosis.