An automated blood culture analyzer may identify a culture as positive when the patient is not infected.
One of the common methods used for monitoring a blood culture is to look for generation of carbon dioxide, which is generated as bacteria digest sugars in the media.
Causes of a sterile release of carbon dioxide:
(1) severe hypercarbia/hypercapnia
(2) severe leukocytosis (with the white cells consuming the sugars)
Causes of false positive bacterial contamination (pseudobacteremia):
(1) skin contaminants introduced at the time of blood specimen collection
(2) contamination of the culture within the laboratory
Other problems:
(1) mixup of specimens between someone with and someone without bacteremia
(2) instrument malfunction
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