One of the major criterion of the modified Duke criteria includes having a positive blood culture for typical infective endocarditis organisms (Strep viridans or bovis, HACEK, Staph aureus, and enterococcus). They must be obtained from two separate blood cultures, or be two positive cultures from samples drawn 12 hours apart, or all of three or a majority of four separate blood cultures (first and last sample drawn one hour apart). Additionally, Coxiella burnetii can fulfill the major criterion, if it is detected by at least one positive blood culture, or IgG antibody titer for Q fever phase 1 antigen, being greater than 1:800.
This major criterion describes endocardial involvement via echocardiogram findings. This can be through observation of an oscillating intracardiac mass on valve or supporting structures, the finding of an abscess, seeing a new partial dehiscence of a prosthetic valve, or the finding of a new valvular regurgitation.
One of the minor Modified Duke criteria is the presence of a fever greater than 38.0 degrees C (100.4 degrees F).
Another minor criterion is the development of immunologic phenomena, such as glomerulonephritis, Osler’s nodes, Roth’s spots, or the presence of rheumatoid factor on serum lab evaluation.
One minor criterion of the Modified Duke criteria is the presence of vascular phenomena. These include evidence of arterial emboli, pulmonary infarcts, conjunctival hemorrhages, and Janeway lesions.
A known predisposition to endocarditis is another minor criterion. This includes having a known, previously diagnosed cardiac lesion, or a history of intravenous drug use.
Microbiological evidence of infection is another minor criterion of the Modified Duke criteria. The presence of a positive blood culture that does not meet a major criterion, as noted above, or serologic evidence of infection with organism consistent with infective endocarditis, but not satisfying major criterion, counts as fulfilling this minor criterion.
Infective endocarditis is diagnosed if the patient has two major criteria.
Infective endocarditis is diagnosed if the patient has one major and three minor criteria.
Infective endocarditis can be diagnosed if the patient presents with five minor criteria.
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