How are transfusion-transmitted bacterial infection (TTBI) cases defined?

Updated: Jan 15, 2017
  • Author: Mudassar Zia, MD; Chief Editor: Emmanuel C Besa, MD  more...
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An important concept in the evaluation of data regarding transfusion-transmitted bacterial infections (TTBIs) is the definition of a case. The Bacthem study provided widely accepted criteria based on the separation of cases into possible, probable, and definite contamination. These are defined as follows [1] :

  • Possible contamination - The blood culture from a recipient grows a bacterial pathogen, with documentation of no other apparent source, but there is failure to isolate the same bacteria from the donor blood product, either because the culture is negative or it could not be done

  • Probable contamination - The blood culture from the recipient is negative or could not be done, but there is definite bacterial growth in the donor blood product.

  • Definite contamination - The blood culture from the recipient and the donor blood product grow the same bacteria.

Another intriguing dimension to TTBI is the fact that bacterial contamination per se does not mean definite production of clinical disease in the recipient. Likely causes of this discrepancy include the following:

  • Insufficient bacterial inocula that may result in a positive culture from the donor product or the recipient but that is not sufficient to produce clinical signs and symptoms

  • Infectivity and virulence of the bacteria under consideration

  • Contamination of the blood during testing procedures

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