WASHINGTON - The Food and Drug Administration (FDA) reports that findings to date indicate that the particles are composed of normal blood substances and that rates of adverse reactions to transfusions have not increased since the blood particles have been observed. All analyses to date of possible infectious agents, chemical contaminants, or blood bag defects have found no abnormalities that indicate a public health risk. Increasing evidence suggests that many of the particles observed may be explained by the use of certain standard, accepted procedures for preparation of red blood cells for transfusion.
Reports of unusual particles initially came from two regions of the American Red Cross (ARC) and involved blood bags from only one manufacturer. However, additional surveillance resulted in similar reports from other ARC and non-ARC centers in many parts of the country and in collection bags from several manufacturers.
Early reports of adverse events in patients who received blood that might have conceivably contained such particles raised the question of whether they could be harmful. However, follow up investigations by the blood centers have so far failed to provide any evidence of any increase in adverse reactions among patients who may have received potentially implicated blood transfusions.
In addition, testing by the Centers for Disease Control and Prevention (CDC) found no evidence of infectious agents or increased levels of a limited number of chemicals. Baxter Healthcare Corporation, a major blood bag manufacturer, in cooperation with the ARC and FDA, has extensively tested their processes and materials, and these tests have identified no unexpected materials or conditions. FDA laboratories have also independently tested some collection bags of the type for which questions of particulates were raised, and have detected normal contents in the blood bags and no contaminants or unexpected chemicals to date.
Studies on both the safety and on the cause of the particulates are ongoing. FDA, CDC, NIH, American Association of Blood Banks (AABB), ARC, America's Blood Centers, state health departments and a number of individual blood centers are all sharing information and many are conducting studies to try to determine why these blood particles are being seen and to detect any possible risk to blood safety.
In one study, to address a possible effect on transfusion safety, the Georgia Division of Public Health, with technical assistance from the CDC, FDA, ARC and AABB, surveyed blood transfusion services in Georgia about the occurrence of adverse events associated with blood transfusion during January 2002 through January 2003. This rate did not significantly change over the 13-month period, and did not increase during January 2003 when the particulates were first noticed.
One theory under investigation by FDA and the blood centers is that the observed particles can result from certain physical conditions of blood handling. Whole blood is composed of red blood cells, plasma, white cells, and platelets. It is a long-term practice in the blood industry, when blood platelets are not being prepared from whole blood, to allow the platelets to remain in red blood cell units during and after processing to remove plasma.
With the availability in recent years of automated methods for platelet collection that yield more platelets from fewer donors,whole blood donations are less commonly used as a source of platelets. In these whole blood donations, it is more efficient to leave the platelets in the RBC fraction of the blood. It is known that platelets sometimes form visible particulates.
Preliminary studies show that the presence of these platelet particles is most common following the preparation of units using methods that allow the platelets to remain with the red blood cells. Some veteran blood bankers think that the observed particles are not unusual, though it is unclear whether the frequency of this phenomenon has increased.
Other possible contributing causes of the observed particles have not been completely ruled out and are still being studied in the laboratory and the field. Additional ongoing investigations include further studies both to detect any potentially related adverse events and to better understand how different methods of blood preparation may contribute to particle formation. These studies may help FDA to determine whether any changes in current practices are desirable.
While these investigations are ongoing, FDA's current thinking is that it is appropriate for blood collection establishments to inspect all blood and blood components using the enhanced procedures that have been in place for the last several weeks. Until these issues are resolved more definitively, FDA believes it is appropriate for blood collection establishments to continue to quarantine any suspect products as a precautionary measure, or else filter the products using procedures that are adequate to remove white cells. Current evidence suggests that such procedures will remove all or most of the observed particulates.
Dependent on further studies of the particulate matter, FDA may issue guidance to the blood industry on appropriate measures needed to keep the blood supply as safe as possible while not unnecessarily affecting the availability of blood products, which are vital to the public health.
FDA wants to emphasize that blood donation is a safe procedure. Continued donations are critical to maintaining a safe and adequate blood supply. For patients who need a blood transfusion, the benefits of transfusion are far greater than the risks. FDA, CDC, and the blood organizations will continue to inform the public as more is known about the particulate matter in blood products.