Factors that may influence the sensitivity of the antibody screen:

1. Cell-to-Serum Ratio · Whenantibody is present in the test system in excess false-negativereactions occur as a result of prozone. · Whenthe antigen is in excess, false-negative reactions occur due to postzone · Aratio of two drops of serum to one drop of the RBC suspension typicallygives the proper balance between antigen and antibody to allowsensitization and agglutination to occur. Note: When an antibodyis weak, the amount of serum in the test system may be increasedto four to ten drops if NO potentiators (tube system), providing moreantibodies to react with the available antigens. 2. Temperature and Phaseof Reactivity · Omitthe immediate spin and room temperature phases to limit the detection ofinsignificant cold antibodies. · Spinand RT phase 3. Length of Incubation · Iftoo little contact time is allowed, too few RBCs will be sensitized · Ifthe incubation time is allowed to continue for too long, bound antibody maybegin to dissociate from the RBCs. · Asaline environment may require an incubation time of 30 minutesto 1 hour · Potentiators mayshorten the incubation time to as little as 10 minutes. 4. Ph · Mostantibodies react best at a neutral pH between 6.8 and 7.2 · Anti-Mdemonstrate enhanced reactivity at a pH of 6.5 · Acidifyingthe test system may aid in distinguishing anti-Mfrom other antibodies