Pre-transfusion Testing: Sample Collection & Testing

• ID & Collection

  • the requisition is generated by physician or other authorized healthcare professional
  • all paperwork/wristbands must have minimum of 2 independent identifiers
  • there is usually additional information like patient name and DOB
  • the test can be STAT, ASAP, or routine
  • ABO and Rh must be determined before transfusion except in emergency situations where there is no time -- give O +/- until the type and cross is done
  • The patient's location (ER, OR, etc) can imply an emergency; ER usually takes precedence
• Ottenberg used minor and major crossmatching
• Tubes

  • can collect a red top tube (no additive) or a lavender top (gel technology)
  • plasma is preferred because you don't get small clots forming which may be confused as aggregates, particularly in the gel technique
  • do not use tubes with clot activators or silicone coating
• The sample

  • cannot be lipemic or hemolyzed
  • certain antibodies produce hemolysis (ABO, P, Lewis, Kidd...)
  • it should not be contaminated with any IV fluid -- always draw below an IV
  • it blood is drawn from a line, the first 5-10mL of blood should be discarded before filling tubes for blood banking
• sample retention and record review

  • check for past adverse reactions to transfusions, special transfusion requirements, and unexpected antibodies in the file - if the patient had one, even it is no longer showing up, must give patient blood free from that antigen. Don't want to risk an anamnestic response
• Pretransfusion testing

  • some facilities require manufacturers to supply selectogen cells taht are homozygous (double dose) for clinically significant antibodies
  • this is because some antibodies show dosage
  • dosage means that the antibodies react better when the antigen is homozygous, and they react weakly with antigens that are heterozygous on the RBCs
• Group O was designated as the universal donor
• It was discovered that patient antibodies to RBCs could be harmful
• In 1939, the Rh factor was discovered, and it was found necessary to recognize incomplete IgG antibodies to Rh