Selecting Positive and Negative Controls for Testing Reagent Anti-serum in the Blood Bank

  1. Each typing serum used in the blood bank must be tested on the day of use for appropriate reactivity with examples positive and negative for the antigen.
  2. To detect deterioration in a typing serum one must use a cell that exhibits the weakest expression of the antigen.
  3. When selecting a cell for testing look at the phenotypes of the cells and select a heterozygous cell, one which is positive for the antigen and its' allele.
  4. In the following example your patient has an anti-Fya identifed in the serum. You must now phenotype the patient for the Fya antigen. In this example we are looking at the Duffy blood group system in which Fya and Fyb are alleles.
    1. The panel below has the Duffy antigens highlighted.
    2. A cell which is positive (+) for Fya and and negative (0) for Fyb is a homozygous Fya cell
    3. If we were to write out the genotype it would be Fya+Fya+, 100% of the antigens on the cell are Fya resulting in a cell which strongly expresses the Fya antigen.
    4. A cell which is positive (+) for BOTH Fya and Fyb is a heterozygous cell, 50% of the antigens expressed are Fya and 50% of the antigens expressed are Fyb resulting in a cell with a weaker expression of both of these antigens. If we were to write out the genotype it would be Fya+Fyb+

        Rhesus Kell Duffy Kidd MNSs P Lewis Lu Results   Fya   Genotype
    1   C D E c e Cw K k Kpa Fya Fyb Jka Jkb M N S s P1 Lea Leb Lua        
    2 R1R1 + + 0 0 + 0 0 + 0 0 + 0 + + 0 + 0 +S 0 + +   Fya Neg   Fyb/Fyb
    3 R1R1 + + 0 0 + + 0 + 0 + + + + + + + 0 + 0 + 0   Fya Pos Hetero Fya/Fyb
    4 R1R1 + + 0 0 + + 0 + 0 + + 0 + + + + + + 0 + 0   Fya Pos Hetero Fya/Fyb
    5 r’r + 0 0 + + 0 0 + 0 + 0 0 + + + + + + 0 + 0   Fya Pos Homo Fya/Fya
    6 r"r 0 0 + + + 0 0 + 0 0 + 0 + 0 + 0 + 0 0 0 0   Fya Neg   Fyb/Fyb
    7 RzR1 0+ + + 0 + 0 0 + 0 + + 0 + + 0 + 0 + 0 + 0   Fya Pos Hetero Fya/Fyb
    8 R1R1 + + 0 0 + + + + 0 + + 0 + + 0 + 0 + 0 + 0   Fya Pos Hetero Fya/Fyb
    9 R1R1 + + 0 0 + + + + 0 + + 0 + + + + 0 + 0 + 0   Fya Pos Hetero Fya/Fyb
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  5. The purpose of the quality control is to detect the weakest expression of the antigen. Which cells would be appropriate for the positive control? Click NEXT