The procedure for the Direct Antiglobulin Test is outlined below:
- Using patient labeled tubes, a 3-5% red cell suspension is prepared using normal saline.
- 1 drop of red cell suspension is added to 4 tubes labeled: Polyspecific, IgG, C3d and Saline Control.
- The cells in the 4 tubes are washed 3 times with normal saline and decanted to a dry cell button.
- 2 drops of each reagent are added to the corresponding tubes and centrifuged at 2500 rpm for 15-20 seconds.
- Tubes are observed and graded for agglutination.
- The polyspecific tube and C3d tube are incubated for 5 minutes to allow more time for complement binding. They are then centrifuged again and observed for agglutination.
Any negative tests in the Polyspecific, IgG or C3d tubes are followed with the addition of 1 drop of check cells to each tube, centrifuged and observed for agglutination. Check cells are added to ensure that the washing process occurred correctly as well as to confirm the addition of reagents.
In most warm autoantibody cases, the Direct Antiglobulin test will be positive.
