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Rapid organism identification and detection of antimicrobial resistance genes directly from positive blood cultures has been a critically important development in the field of clinical microbiology. Testing for these is frequently accomplished using multiplexed assays that detect the presence of nucleic acids from specific microorganisms commonly found in patients with bloodstream infection. When combined with active antimicrobial stewardship interventions, such technologies have been shown to lead to improved time to initiation of appropriate antimicrobial therapy, and in turn improved patient outcomes.

Recently, there have been several Class 2 recalls issued by the U.S. Food and Drug Administration (FDA) because of increased risk for false-positive detections with these assays due the presence of DNA from non-viable organisms present in certain blood culture media. Such analytical performance problems put the clinical laboratories in the difficult situation of reporting potentially inaccurate results for positive blood cultures. Here, we will describe this issue in more detail, including optional strategies for the clinical laboratory to address these issues.