Intermediate blood mixtures. Bags of blood pooled using components of donor blood, a process called component pooling. Donor blood is separated into its component parts for more efficient use of the blood. These components are mixed back together to produce the required blood. This blood is labelled as having red blood cells from group O (universal donor blood group) and it is depleted of platelets (needed for clotting). It also has the Rh (rhesus) D antigen and is labelled D-positive. Buffy coat refers to the white blood cells (lymphocytes). The blood mix displayed here is not yet suitable for clinical use. It is an intermediate product that needs to have more blood components added.