3. Explain how Coombs reagents are produced.
4. Explain the role of Coombs control cells in antiglobulin testing.
5. Explain the mode of action of the Coombs control cells.
8. Explain why a lavender top tube is best for DAT testing.
Name two reasons for a false positive DAT, and explain why each would produce a false positive result.
False positive reactions can also occurred when performing this test. These would not be detected by the use of Coombs Control Check Cells. Reasons for a false positive reaction could be the following:
Using improper sample (clotted cells instead of EDTA for Direct Antiglobulin Test, DAT)
Spontaneous agglutination (cells heavily coated with IgM)
Non-specific agglutination ("sticky cells")
All of these reactions would be the result of cells appearing to agglutinate, or actually agglutinating. Using a clotted tube for the DAT may allow complement to become activated in the test tube since calcium ions are free to be part of the complement cascade.