Direct Antiglobulin Test

Description: 
The Direct Antiglobulin Test (DAT) is used to detect the presence of IgG or complement on the surface of a patients red cells. Certain at risk groups are routinely tested including neonates with jaundice, patients with haematological disorders and those with unexplained anaemia’s, especially if spherocytes are present.
A broad spectrum Antihuman Globulin (AHG) containing Anti-IgG and Anti-C3d is used; if a sample tests positive it is then tested against monoclonal AHGs to determine the specificity.
Clinical details: 
For further information please refer to the GSTT Clinical Guidance Policy.
http://tww-wafr/WAFR-FAD/Applications/ClinicalGuidance/User/Details.aspx?id=4971
Synonyms or keywords: 
Coombs test
Department: 
Blood Sciences Department
Location: 
St Thomas' Hospital
Sample type and Volume required: 
Griener Vacutte K3EDTA 6 mls whole blood for adult tube (Pink top)
Griener Vacutte K2EDTA 4 mls whole blood for adult tube (Purple top)
K3EDTA paediatric 1 ml whole blood tube (pink top)
Call in advance: 
No
Turnaround time: 
1 working day. This test can be performed urgently depending on clinical details and discussion with the laboratory.
Special sample instructions: 

Samples for Transfusion testing must include the following minimum details:

All details must be legibly handwritten on the blood tube.

Surname (in full)

Forename (in full)

GSTT Hospital Number*

Date of Birth

Date and time of sample

Sex

Signature of the person taking the sample

*Most samples from GP surgeries may be accepted without a hospital number. However samples for transfusion testing on antenatal patients must always have a GSTT hospital number.

Factors affecting the results:

Samples more than 48 hours old or that have been refridgerated cannot be tested. Certain drugs are known to cause a positive DAT.  Samples must be adequately anti-coagulated. Clotted samples cannot be used for this test as free red cells are required.

Criteria for acceptance / rejections of sample
Storage and transport: 
Samples are stored for 7 days.
Contacts:
Blood Transfusion Laboratory at Guy's and St Thomas' Hospital
020 7188 4774
Blood Transfusion Laboratory
St Thomas' Hospital
North Wing, 5th Floor
St Thomas' Hospital
Westminster Bridge Road
London SE1 7EH

Blood Transfusion Laboratory
Guy's Hospital
Southwark Wing, 4th Floor
Great Maze Pond
London SE1 9RT
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Blood Transfusion Laboratory at Guy's and St Thomas' Hospital

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Last updated: 08/08/2022