A purple tope tube (EDTA) is the preferred sample for pretransfusion testing. A red top tube (clotted specimen) can be used if necessary. A tiger top tube (serum separator tube) cannot be used because the separator gel can interfere with agglutination reactions. Specimens expire in 3 days -- blood requested after that needs a new sample sent. You may make exceptions if the patient has not been transfused or pregnant in the last 3 months. Neonates are also an exception -- see neonatal protocol.
A. Group, screen and hold. ABO grouping, D typing and antibody screening performed. Indicated for patients in whom transfusion is possible, but not certain. If antibody screen is positive, the antibody will be identified and the physician will be contacted to see if crossmatched blood will be needed. If physician is unsure, if transfusion is now certain, or if the patient is a pre-op, two units of blood will be crossmatched, if the antibody is clinically significant.
B. Type and crossmatch. ABO grouping, D typing, antibody screening, and crossmatch of RBC units. We will leave units crossmatched up to 24 hours in most cases. If not used, the unit is released into inventory again. Units are not crossmatched to more than one patient at a time at PMH, ZLUH or CMC.
A tube is required for ABO typing of the recipient to determine if it matches the autologous unit(s). An antibody screen is done but crossmatching is not required.
Once during each admission, a tube is required for ABO and Rh typing. Crossmatching is not performed.
Time required. Pretransfusion testing requires a minimum of one hour to perform. Most of the time is the incubation necessary for the antibody screening rather than the ABO or Rh typing or crossmatching. If no antibodies are found, an immediate spin crossmatch will be performed, taking only approximately 10 minutes. If clinically significant antibodies are present, a LISS crossmatch with antiglobulin phase must be performed, taking 30 minutes or so. In an emergency, blood can be released without testing being completed, but all testing will eventually be done after the infusion.
Review of records. When pretransfusion testing is requested on any patient, old blood bank records must be consulted to verify that the current blood type matches the previous blood type on record. If there is a discrepancy, you may be called to investigate. The most likely possibilities are mislabelled specimens then or now, or that another individual is using one person's PMH card. Ask for another specimen from the current admission. Written records of blood type can never be used as the only indication of blood type.
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