DAT FINAL KEY CONCEPTS AND PRACTICE
QUESTIONS
◉ When do we use AHG technique?
Answer: In antibody screening and identification, antigen typing,
and in direct antiglobulin testing.
◉ In DAT, where does the sensitization step occur?
Answer: in the body
◉ Direct antiglobulin tests determine what?
Is IgM coating detected with this form of testing?
Is IgA coating detected?
What is in the control tube of this test? What results do you look for
in the control and what do they mean?
Answer: DAT determines *in vivo* coating of red blood cells by IgG
antibody, by complement, or by both IgG and complement.
, IgM coating is not detected, except by complement that may have
been activated.
IgA coating is not detected.
The control tube consists of the patient's RBCs and saline. The
control tube should be negative. If the control tube is positive it
suggests polyagglutination and we cannot really trust anything going
on in the DAT tube if the control is positive.
◉ Briefly list the steps in direct antiglobulin testing.
Answer: Collect EDTA sample. (antigen-antibody reaction occurs in
the body) Wash the cells to remove free plasma antibody. Add AHG
(polyspecific). If the cells were coated in vivo, then the test will be
positive (agglutination will occur). In a positive DAT test with
polyspecific AHG, you would need to continue testing to a
monospecific AHG to determine if the cells were coated with IgG or
with complement (C').
◉ What type of tube is used in direct antiglobulin test? Why do we
use this tube?
Answer: Sample is drawn in a lavender top tube. The EDTA will not
allow blood to clot, if the tube allows blood to clot, there could be a
false positive DAT because clotting can cause the complement
cascade to start.
QUESTIONS
◉ When do we use AHG technique?
Answer: In antibody screening and identification, antigen typing,
and in direct antiglobulin testing.
◉ In DAT, where does the sensitization step occur?
Answer: in the body
◉ Direct antiglobulin tests determine what?
Is IgM coating detected with this form of testing?
Is IgA coating detected?
What is in the control tube of this test? What results do you look for
in the control and what do they mean?
Answer: DAT determines *in vivo* coating of red blood cells by IgG
antibody, by complement, or by both IgG and complement.
, IgM coating is not detected, except by complement that may have
been activated.
IgA coating is not detected.
The control tube consists of the patient's RBCs and saline. The
control tube should be negative. If the control tube is positive it
suggests polyagglutination and we cannot really trust anything going
on in the DAT tube if the control is positive.
◉ Briefly list the steps in direct antiglobulin testing.
Answer: Collect EDTA sample. (antigen-antibody reaction occurs in
the body) Wash the cells to remove free plasma antibody. Add AHG
(polyspecific). If the cells were coated in vivo, then the test will be
positive (agglutination will occur). In a positive DAT test with
polyspecific AHG, you would need to continue testing to a
monospecific AHG to determine if the cells were coated with IgG or
with complement (C').
◉ What type of tube is used in direct antiglobulin test? Why do we
use this tube?
Answer: Sample is drawn in a lavender top tube. The EDTA will not
allow blood to clot, if the tube allows blood to clot, there could be a
false positive DAT because clotting can cause the complement
cascade to start.
