Bacterial Contamination of Blood Products and the Value of Pre-Transfusion Testing

Abstract

There has been a dramatic increase recently in the number of reports of septic episodes associated with both red cell and platelet concentrate transfusions. These reports suggest that transfusion-associated septic reactions may occur as often as 1 per 4000 platelet transfusions, however, the true incidence of the bacterial contamination of stored cellular blood components has not yet been established. Recently developed automated techniques for the detection of bacteria are much more rapid than direct plating techniques. Such rapid techniques can be used to monitor the sterility of cellular blood products with greater sensitivity than Gram staining; using a small aliquot of the blood product taken soon after collection. Using such equipment, the incidence of bacterial contamination of 15,838 random donor platelet concentrates collected over a six-month period was determined and evidence of bacterial contamination was found in 32. Seven were classified as confirmed, 10 as unconfirmed and 12 as non-confirmed positives. The confirmed positivity rate was thus 4.4 per 10,000. This rate represents the minimum incidence of bacterial contamination of platelet concentrates and the true rate is likely higher, as some of the unconfirmed positives are likely to have been found to be positives, had the original platelet concentrate been available for culture. The true positive rate is therefore estimated to be between 4.4 and 10.7 per 10,000. Given this rate of bacterial contamination, it is our contention that all platelet concentrate units be monitored for bacteriologic sterility prior to their issue. The cost of such screening would be of the same order of magnitude as that for each of the tests currently performed to screen donors for transfusion-transmitted diseases. The addition of a bacteriologic surveillance program could contribute significantly to a blood supply with reduced risk and would enable relevant scientific advances, such as the prolongation of the storage time to be fully implemented to optimize patient care as well as blood product utilization.