What is the prevalence of false-negative and false-positive lab findings in infective endocarditis (IE)?

Updated: Jan 03, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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The criterion standard test for diagnosing IE is the documentation of a continuous bacteremia (>30 min in duration) based on blood culture results.

Exceptions are observed in patients with prosthetic valve endocarditis (PVE) and right-sided IE. About 5-10% of patients with IE have false-negative blood culture results. Prior use of antibiotics is the most common cause of false-negative blood culture results. Other causes include fastidious organisms and inadequate blood volume; a blood-to-broth ratio of 1:10 is needed. Currently, with modern automated blood culture systems, fastidious organisms such as nutritionally variant streptococci and members of the HACEK group rarely cause culture-negative IE.

As many as 50% of positive blood culture results have been estimated to be falsely positive. This rate has probably decreased, but false-positive blood culture results remain a major diagnostic challenge. One such result can lead to 4 days of unnecessary patient hospitalization.

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