Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Investigation of acute/delayed haemolytic transfusion reaction (alloimmune reactions following transfusion), autoantibodies (including those associated with warm and cold autoimmune haemolytic anaemia (AIHA)), drug-induced haemolytic events and haemolytic disease of the fetus and newborn (HDFN). The DAT is used to demonstrate coating of red blood cells with complement (C3d) and/or IgG in-vivo. A positive DAT may result in shortened red cell survival and must be evaluated with clinical information to ascertain the significance of the test. A DAT is originally performed using a polyspecific antihuman globulin (AHG) reagent capable of detecting both IgG and C3d. If positive by this reagent then a differential DAT will be performed using specific anti-IgG and complement reagents to identify the type of reaction (e.g. IgG only, C3d only or both). An eluate may be performed on samples expressing an IgG positive DAT to identify any antibody bound to the red cells.
Specimen container paediatric:
1mL K2 EDTA or 6mL K2 EDTA or 4mL K2 EDTA
Specimen container adult:
6mL K2 EDTA (pink top) or 4mL K2 EDTA (purple top)
Minimum volume paediatric:
0.5mL
Minimum volume adult:
1mL
Special requirements:
Test can be ordered via EPR PowerChart and taken with the BloodTrack bedside sample labelling system.
The Trust operates a zero tolerance policy. Deviation from Trust Sample Labelling Policy will result in the sample being rejected and a repeat requested.
Sample stability :
Short term storage: 24 hours at room temperature. Long term storage: 7 days at 4-6°C
Transport requirements:
Sample should be transported to Laboratory Medicine Reception via GP courier, hospital air-tube system or hand delivered to maintain storage conditions. Samples must not be subjected to extreme hot or cold conditions prior to testing.
Add on test:
Request for add on must be discussed directly with the Transfusion laboratory.
FH: 0191 2237849
RVI: 0191 2824435
Interpretation:
A negative DAT suggests that no antibody is attached to the red blood cell. A positive DAT suggests that there are antibodies attached to the red cell. The stronger the reaction, the more positive the test and the greater the amount of antibody bound to the red cell. However, the strength of the reaction does not always reflect the clinical severity. Medical history and clinical examination is required to determine if a positive DAT is due to a transfusion reaction, autoimmune reaction, an infection, a medication, or HDFN. A small percentage of the normal population will be DAT positive and not experience any haemolytic anaemia.
Factors affecting result :
Samples which are old (>24 hours). Incorrect specimen type received. Clotted, haemolysed, icteric or lipaemic samples. Insufficient plasma provided.