Packed red blood cells do not have an antibody, since the greatest risk of Rh incompatible blood is to current or future pregnancies. For RBCs, type O negative blood is considered a "universal donor" as recipients with types A, B, or AB can almost always receive O negative blood safely. Type AB positive is considered a "universal recipient" because they can receive the other ABO/Rh types safely. These are not truly universal, as other red cell antigens can further complicate transfusions. There are many other human blood group systems and most of them are only rarely associated with transfusion problems. A screening test is
Jehovah's Witnesses and blood transfusions eating blood to prohibit the medical transfusion of human blood. Osamu Muramoto has argued that the refusal by Jehovah's Witnesses of "life-saving" blood treatment creates serious bio-medical ethical issues. He has criticized the "controlling intervention" of the Watch Tower Society by means of what he claims is information control and its policy of penalising members who accept blood transfusions or advocate freedom to choose blood-based treatment. He says the threat of being classified as a disassociated Witness and subsequently shunned by friends and relatives who are members coerces Jehovah's Witnesses to accept and obey the prohibition on blood transfusions. In