Time Frame 15 minutes. Student should strive to be able to perform multiple procedures simultaneously.

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Valerie Richardson
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1 Name Direct Antiglobulin Test (DAT) (Direct Coombs) Principle The DAT detects the in vivo sensitization of RBC with IgG incomplete or non-agglutinating antibodies. After thorough washing of RBC with saline antiglobulin serum is added. Agglutination is a positive reaction and indicates that the patient cells are coated with antibody. Clinical Significance The DAT is utilized to aid in the diagnosis of hemolytic disease of the newborn and autoimmune hemolytic anemia to investigate possible transfusion reactions and RBC sensitization by drugs. Acceptable Student Result Range The DAT must be performed with 100% accuracy. Time Frame 15 minutes. Student should strive to be able to perform multiple procedures simultaneously. Specimen EDTA (preferred), whole blood, or clot tube. Reagents Blood bank reagent rack 0.85% NaCl Procedure Refer to MLAB 2431 procedure cards. Interpretation of Results Agglutination of the red blood cells by the anti-human globulin serum is indicative of in-vivo sensitization of the cells. If the patient is an adult, a history must be obtained which includes the following: 1. Transfusion history 2. Medications Summer MLAB 2360 DAT! 1

Clinical Significance The DAT is utilized to aid in the diagnosis of hemolytic disease of the newborn and autoimmune hemolytic anemia to investigate possible transfusion reactions and RBC

2 3. Patient's diagnosis An eluate should be performed to determine the specificity since, especially in transfused patients, a positive DAT may be indicative of a delayed hemolytic reaction. If the patient is an infant a Type and Screen must be performed on the mother of the infant and an ABO/D type (forward only) must be performed on the infant. An appropriate elution technique must be performed to determine the specificity of the antibody coating the infant's cells. (See flow chart.) Cordblood Workups 1. Perform DAT s on the CORDBLOOD specimens, and perform an ABO/D type on the infant as necessary. (TRhs are not optional if mother is D negative.) 2. If a positive is obtained, look at the CORDBLOOD flowchart (on the following page) to determine what additional testing must be done. 3. Once the appropriate work has been completed, fill out the HDN worksheet with interpretations of work done on baby and mom. 4. Under interpretation, state the of elution which should then be performed AND your expected results. EXAMPLE: Mom Antibody screen Antibody ID Baby Baby s DAT Interpretation: A positive positive Anti-E A positive positive I would need to perform an acid elution on the baby s cord cells. I would expect to elute an anti-e from the baby s cord cells. Summer MLAB 2360 DAT! 2

An appropriate elution technique must be performed to determine the specificity of the antibody coating the infant's cells. (See flow chart.) Cordblood Workups 1.

3 Cordblood Direct Antiglobulin Test (DAT) DAT Negative DAT Positive Mom D pos Mom D neg ABO/D type cord cells T&S Mom nothing more ABO/D type cord cells Screen negative & Mom is group O, and baby is A or B Screen is Positive D neg baby D pos baby Lui Freeze elution on cord cells Panel on Mom No RhIg RhIg needed Interpret results ID antibody in for Mom Mom s serum Acid eluate on cord cells Identify antibody in cord eluate For D negative mothers with a DAT positive baby, RhIg candidacy is determined by identification of the antibody coating baby s cells. If due to immune anti-d (determined by mother s history), she is NOT an RhIg candidate. If due to passively acquired anti-d (from her antenatal dose of RhIg - determined by mother s history), she IS a candidate. If due to any other immune antibody (anti- K, anti-fy, etc.), she IS a candidate. Summer MLAB 2360 DAT! 3

antibody in cord eluate For D negative mothers with a DAT positive baby, RhIg candidacy is determined by identification of the antibody coating baby s cells.

4 Summer MLAB 2360 DAT! 4

5 Mom's Type Date & Rh Mom's Name and Hospital Number Blood Bank Clinical Cordblood DAT Worksheet Name DAT A B A,B Cell Typing with Anti- D DC D D u u C Interp RhIg Yes/No Tech Time Summer MLAB 2360 DAT! 5

6 Name Date Elution Studies Recording Results Patient Name Cells A1 B S1 S2 S3 Reactions with Eluate Reactions with Last Wash Control Interpretation: Summer MLAB 2360 DAT! 6

7 Only test that can be batched Direct Antiglobulin Test (DAT) Cordbloods Tube for DAT mom's last name Tube for DAT mom's last name Tube for DAT mom's last name Patient #1 Cord cell suspension name of mom (complete) and Hospital Patient #2 Cord cell suspension name of mom (complete) and Hospital Patient #3 Cord cell suspension name of mom (complete) and Hospital Summer MLAB 2360 DAT! 7

name of mom (complete) and Hospital Patient #2 Cord cell suspension name of mom (complete) and

8 Summer MLAB 2360 DAT! 8

Direct Antiglobulin Test (DAT)

Exercise 8 Direct Antiglobulin Test (DAT) Objectives: 1. State the purpose for performing the DAT. 2. State what a positive DAT indicates. 3. List the reagents which are used for performing the DAT. 4.