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Interpretation of Results


Interpretation of Results

This educational webpage is based on the Blood Culture Educational Booklet that you can access HERE.

The microbiology laboratory can provide useful information to clinicians to help them determine whether a blood culture sample is a true positive or a false positive (contaminant). 

For example, the identity of the micro-organism isolated can help determine if the culture is contaminated, and the number of cultures positive with the same organism can help predict true infections.56 Time to positivity is also a factor used to determine potential contamination as contaminants usually have a delayed (longer) time-to-detection due to a lower overall bio-load.

Laboratories should consult with their medical director to create an algorithm which helps determine whether or not an isolated organism is a contaminant vs. an infective agent.

Models, such as the algorithm below, can give guidance only on the interpretation of blood culture results.40 These guidelines should be used in conjunction with clinical guidelines, e.g. patient’s full blood count, presence of catheters, radiological findings, etc.

The content on this website and associated materials do not constitute medical advice and should not be considered a substitute for the individual professional judgement of any physician or other health care practitioner regarding the appropriate course of action for a particular patient. All recommendations should be independently reviewed with appropriate medical staff in light of the needs of any particular institution and its patients. bioMérieux makes no guarantee or representation regarding the accuracy, completeness, or usefulness of this information for any particular purpose, including but not limited to any cost savings.