Du Test in Blood Bank: Introduction, Principle, Procedure, Result Interpret

Du Test in Blood Bank: Introduction, Principle, Procedure, Result Interpretation and Clinical Significance

Introduction of Du Test in Blood Bank

Du test helps to distinguish true Rho (D) negative from Du positive. Du is the weak expression of the RhD antigen (Du) and is widely used to describe cells that have a quantitative reduction in the expression of their RhD antigen.

Principle of Du Test

Red blood cells that react weakly or not at all in direct agglutination test with anti-D may react with anti-D on the presence of Coomb reagent incubating at 37° C and examine for agglutination. Washing the red cells is mandatory to remove unbound antibody (IgG anti-D) prior to testing with anti-IgG.

Requirements for Du Test in Blood Bank

Equipment and reagents required are given below-

Test sample
Test tubes (10 × 75 mm)
Test tube rack
Pasteur pipette or micro pipette
Marker
Container for waste disposal
Tissue paper
Incubator or water bath (37°C)
Centrifuge
5% cell suspension of RBCs
Normal saline
View box/Microscope
Clean grease-free glass slides
Anti-D sera
Antihuman globulin (Coomb’s reagent)- containing anti- IgG
Bovine albumin 22% ( control)

Procedure of Du Test

Prepare 5% cell suspension of red blood cells as follows–Mix 5 drops ( 50µl each) of sedimented RBCs with 2 ml of normal saline. Centrifuge at 1500 RPM for 1 minute and discard the supernatant. Put 4 ml of normal saline into the sedimented RBCs and mix it well. This preparation gives a 5% suspension of RBCs.
Take one tube and label it as ‘T ‘.
Add in it one of the Anti- D sera.
Label the second tube as ‘C’ and add in it one drop of 22% bovine albumin.
By using a Pasteur Pasteur pipette, add one drop of the cell suspension to each of the two test tubes, mix well.
Incubate the test and the control for at least 15 minutes at 37°C.
After incubation, wash the cells in each tube three times with fresh normal saline (for each washing add a test tube full of normal saline).
Decant the tubes completely after the last washing.
To each tube, add two drops of Coomb reagent.
Mix the contents of the tube gently and centrifuge at 1,500 RPM for 1 minute.
Resuspend the cells by gentle agitation and examine macroscopically for agglutination. If there is confusion, confirm the results microscopically.

Result Interpretation of Du Test

Result Interpretation of Du test are as follows-

Du Test- Introduction, Principle, Procedure, Result Interpretation and Clinical Significance

Key

O/-: No agglutination

+ : Agglutination

Keynotes on Du Test in Blood Bank

Red blood cells which agglutinate in the presence of Anti- D and Bovine control, cannot be accurately tested for the Du antigen.
A Du positive donor should not be used for transfusion purposes.
Du positive recipients must receive only Rh-negative blood.
Invalid positive test results may be obtained with antiserum if the blood tested is from a person with autoantibodies or abnormal serum proteins. The simultaneous use of 22% bovine serum control is useful for the detection of such false-positive results.
Antihuman globulin (Coomb’s reagent) can be made by injecting purified human gammaglobulin into one colony of rabbits and purified human beta-globulin components into another colony of rabbits ( complement).
After a certain amount of time has passed, the serum from these rabbits is taken and combined to create Anti-human globulin.

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