ANSWERS WITH SOLUTIONS 2024
Direct Antiglobulin Test (DAT) - ANSWER -Detects IgG or complement bound to RBCs in vivo
-In the procedure, AHG reagent is added after the RBCs have been washed
-Agglutination demonstrates whether IgG or complement was attached to the RBCs
DAT false positive - ANSWER -Overcentrifugation
-Contaminated reagents
-Insufficient washing of RBCs
-Test tubes allowed to stand after centrifugation
-RBCs left in suspension for extended time before testing
-Clotted sample
-IV immune globulin
-Spontaneous agglutination (IgM)
DAT false negative - ANSWER -Improper cell washing (free antibody/complement remains and reacts
with AHG; no Check Cells react with antibodies)
-Delay in adding AHG after washing step (antibody elutes off and attaches to AHG)
-Inactive, or forgotten, AHG
-Improper specimen agitation before interpretation