There are two arms to the prion filtered red cells in surgery and multi-transfused patients (PRISM) trial—one control arm (patients receiving standard red cells) and one filter arm (patients receiving prion filtered red cells). Patients in both arms of the trial are followed up for six months in case of late complications, especially formation of antibodies to red cells which might affect future transfusions. This means that although it is anticipated that recruitment to the filter arm will be complete in 2010, follow up will continue to mid-2011. It may be clear at that point that the filters do not cause unexpected complications. As a comparison, a similar number of patients in the control arm are also being followed up. This will complete in 2011, with follow up until 2012.
Since the prion filtered red cells in surgery and multi-transfused patients (PRISM) study is still ongoing, there are no publications related to it as yet. The Irish Blood Service has presented an abstract on its clinical experience with prion filtered red cells at the American Society for Haematology in December 2009.
To ask Her Majesty's Government how many persons have been transfused with prion filtered red cells as part of the PRISM trial; and how many units of prion filtered red cells have been transfused in the United Kingdom as part of the PRISM trial. [HL1591]
Other than the ongoing prion filtered red cells in surgery and multi-transfused patients (PRISM) study, we are aware of two other studies that have assessed the safety of red cells filtered using the P-Capt filter:
a small study conducted by the manufacturer in healthy volunteers where the subjects received one unit of prion filtered red cells; and
a study of 20 patients conducted in Ireland where patients were specifically followed up for evidence of adverse events. The Irish Blood Service has now transfused around a further 180 units of red cells filtered using the P-Capt filter, but these patients have not been specifically followed up.
As far as we are aware, the PRISM study is the only controlled clinical study of red cells filtered using the P-Capt filter that is currently recruiting patients.