The Direct Antiglobulin Test seems super-simple, but there’s more to it than meets the eye! Sue Johnson joins Dr. Chaffin to discuss.

Sue Johnson

Susan Johnson, MTSM, MT(ASCP)SBB

The DAT (also known as the “Direct Coombs” test) is really a basic and easy test to do. For such a simple test, however, most blood bank students struggle with the concepts, as do many clinicians! The DAT leads to discussions of autoantibodies, adsorptions, and elutions, oh my! Never fear, though, my friend Sue Johnson is a master teacher who has explained the essentials of the DAT to thousands of students! She is my guest on this episode to guide us to great clarity on this most excellent immunohematology test.

This is a fun episode! Whether you are a pure beginner or an experienced blood banker, you will come away with a much better understanding of why the DAT is so important!

About My Guest: Sue Johnson, MSTM, MT(ASCP)SBB is the Director of Clinical Education at BloodCenter of Wisconsin (a part of Versiti). She also is the director of the Specialist in Blood Banking Program at BCW and the Transfusion Medicine Program at Marquette University. Sue is Associate Director of the Indian Immunohematology Initiative, a program designed to improve general immunohematology knowledge in South Asia. She is a sought-after speaker and world-class immunohematology expert. Sue also appeared on episode 050 and 051 of this podcast (in both cases, discussing Pretransfusion Testing).

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DISCLAIMER: The opinions expressed on this episode are those of my guest and I alone, and do not reflect those of the organizations with which either of us is affiliated. Neither Ms. Johnson nor I have any relevant financial disclosures.

The images below are generously provided by Sue Johnson. The featured image seen in the podcast episode list and on Facebook and Twitter was illustrated by Jenny O’Connor, MLS(ASCP)SBBCM.

Johnson Slide 1
Johnson Slide 2 - DAT Reagents
DAT procedure 1 - Fresh sample from patient to be tested
DAT procedure 2 - Wash thoroughly
DAT procedure 3 - Washing removes interfering free antibody (compare to slide 2)
DAT procedure 4 - Anti-human globulin agglutinates coated RBCs
Johnson Slide 7 - Complement deposition on RBCs (note C3b and C3d)
Johnson Slide 8 - Causes of positive DAT (1 of 3)
Johnson Slide 9 - Causes of positive DAT (2 of 3)
Johnson Slide 10 - Causes of positive DAT (3 of 3)
Johnson Slide 11 - Factors to consider when evaluating DAT results
Johnson Slide 12 - AMAZING flowchart for DAT evaluation!

Don’t miss these videos for a visual look at what Sue described:

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