Antiglobulin Testing Immunohematology Review 460
DIRECT (DAT) INDIRECT (IAT)
Detects
Specimen
Incubation
Application
False positives
False negatives
In vitro sensitization of RBCs by IgG ab
Serum, plasma, RBCs
Serum or plasma with reagent RBCs or RBCs with
reagent antiserum
Ab screen, xmatch, RBC phenotyping, weak D testing
Cells with pos DAT
Overcentrifugation
Same as DAT, plus over- or underincubation
In vivo sensitization of RBCs by IgG ab
EDTA red cells preferred
None required
HDFN, tf rxn, autoimmune hemolytic anemia,
drug-induced hemolytic anemia
Complement binding in vitro if RBCs are taken from
red-top tube & broad-spectrum AHG used
Septicemia
Contamination of specimen
Wharton’s jelly in cord blood
Over-reading
Overcentrifugation
Interruption in testing
Contamination, improper storage, or outdating of AHG
Failure to add AHG
Neutralization of AHG from inadequate washing
Dilution of AHG by residual saline
Over- or undercentrifugation
