Packed red blood cells Rh type, specifically the phenotype, and the "screen" refers to testing for atypical antibodies that might cause transfusion problems. The typing and screening are also performed on donor blood. The blood groups represent antigens on the surface of the red blood cells which might react with antibodies in the recipient. The ABO blood group system has four basic phenotypes: O, A, B, and AB. In the former Soviet Union these were called I, II, III, and IV, respectively. There are two important antigens in the system: A and B. Red cells without A or B are called type O, and
Jehovah's Witnesses and blood transfusions decide whether they could conscientiously accept fractions used from blood for purposes such as vaccination. This position has been expanded on since; the pre-formatted Durable Power of Attorney form provided by the Watch Tower Society includes an option for Jehovah's Witnesses to "accept all fractions derived from any primary component of blood." In 1964, Jehovah's Witnesses were prohibited from obtaining transfusions for pets, from using fertilizer containing blood, and were even advised (if their conscience troubled them) to write to dog food manufacturers to verify that their products were blood-free. Later that year, it was stated that doctors or nurses