Current status of bacterial contamination of autologous blood for transfusion

Autologous transfusion, although not without risk, does decrease the risk of transmitted diseases via homologous transfusion. However, strict quality control is required for autologous transfusion. In Japan, a recent enactment requires that written informed consent be obtained prior to blood transfusion, which therefore requires that clinicians provide sufficient explanation of the risks involved with this procedure. To the best of our knowledge, this is the first study to comprehensively evaluate the manner in which the safety of autologous blood transfusion can be compromised by bacterial contamination. For a 24-month period, between April 1996 and March 1998, bacterial contamination of all kinds of autologous blood samples was tested by sampling the culture immediately prior to transfusion. Subculturing, identification and susceptibility testing of the isolates were performed. From the 287 units of all kinds of autologous blood transfused, 18 were culture positive (6.3%). Positive blood cultures were obtained in two of the 59 units (3.4%) of autologous transfusion donated preoperatively (ATDP) that was infused intraoperatively, in three of the 117 units (2.6%) of hemodilution/autologous transfusion (HAT) and in three of the 81 (3.7%) of ATDP infused postoperatively. There was a high percentage (33.3%) of positive blood cultures in the cases of intraoperative blood salvage (IOBS). The total rate of positive blood cultures was 6.3% including IOBS and 3.1% excluding IOBS. The most common microorganism isolated from autologous blood was coagulase-negative Staphylococci in 12 of 18 culture-positive units (66.7%). Alpha Streptococcus uiridans was isolated in 2 units (11%) and Staphylococcus aureus was isolated in 1 unit (5.5%). However, none of the patients who received the culture-positive autotransfusion blood showed clinical signs or laboratory findings of bacteremia. Safe ATDP is threatened by bacterial contamination that can be introduced by numerous sources, such as the donors' blood, the skin at the site of venipuncture, the environment and the phlebotomist's finger. In the cases of IOBS, protection against bacterial contamination at the surgical site is crucial. Here we discuss the relevance of our findings to the efforts to minimize the risks of contamination associated with autologous blood transfusion; risks that must be communicated to the patient in the process of informed consent. Continued research is required to identify the safest method of autologous blood transfusion.