Diagnosing Endocarditis

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.