1. Check past records for known ABO groups
2. Check diagnosis for leukemia
3. Use anti-A,B in case the A antigen is only weakened
4. Use monoclonal typing sera, as they are very sensitive
5. Read microscopically for weak agglutination and MFA
6. Try secretor status tests as a secretor will secrete his true ABH antigens. As QC, set up known secretor and non-secretor salivas.
7. Try adsorption and elution studies with anti-A: Incubate the patient's red cells at 4°C for 4 hours or overnight to try to adsorb the anti-A onto them. Perform an elution on the red cells and test the eluate against A₁ and O cells. If anti-A is in the eluate, only the A₁ cells should agglutinate and this confirms the presence of the A antigen on the patient's cells. As QC on the elution, test the last wash to be sure it does not contain anti-A.

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©1999 Division of Medical Laboratory Science
University of Alberta

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