What is the purpose of the Comb's control in the ABO testing procedure?

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Multiple Choice

What is the purpose of the Comb's control in the ABO testing procedure?

The key idea is to confirm that the antiglobulin (AHG) reagent is present and works. The Coombs control uses sensitized red cells that already carry IgG antibodies. When AHG is added, if it’s active and properly included in the run, it will bind to those IgG on the control cells and bridge them, producing agglutination. This shows the AHG reagent is functioning and was added correctly, so a negative result in the actual test can be trusted. If the control fails to agglutinate, it signals a problem with the AHG reagent or the procedure, making the test results unreliable. This control does not determine ABO type and is not about detecting spontaneous RBC agglutination; it’s a built-in check on the AHG step.

The key idea is to confirm that the antiglobulin (AHG) reagent is present and works. The Coombs control uses sensitized red cells that already carry IgG antibodies. When AHG is added, if it’s active and properly included in the run, it will bind to those IgG on the control cells and bridge them, producing agglutination. This shows the AHG reagent is functioning and was added correctly, so a negative result in the actual test can be trusted. If the control fails to agglutinate, it signals a problem with the AHG reagent or the procedure, making the test results unreliable. This control does not determine ABO type and is not about detecting spontaneous RBC agglutination; it’s a built-in check on the AHG step.

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