Newcastle Laboratories

Direct Antiglobulin Test (DAT)

Clinical Background:

Request Reason: Investigation of acute and delayed haemolytic transfusion reactions (alloimmune reactions following transfusion), autoantibodies (including those associated with warm and cold autoi...

Request Reason: Investigation of acute and delayed haemolytic transfusion reactions (alloimmune reactions following transfusion), autoantibodies (including those associated with warm and cold autoimmune haemolytic anaemia’s (AIHA)), drug-induced haemolytic events and haemolytic disease of the fetus and newborn (HDFN). The DAT is used to demonstrate if red blood cells have been coated with complement (C3d) and/or antibodies (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. DAT’s are originally performed using a polyspecific antihuman globulin (AHG) reagent capable of detecting both IgG and C3d. If found to be 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.

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Test Details

  • Discipline:

    Transfusion

    Transfusion

  • Specimen Container Adult:

    6mL K2 EDTA (Pink Top) or 4mL K2 EDTA (Purple Top)

    6mL K2 EDTA (Pink Top) or 4mL K2 EDTA (Purple Top)

  • Specimen Container Paediatric:

    0.5mL K2 EDTA (Pink Top) or 6mL K2 EDTA (Pink Top) or 4mL K2 EDTA (Purple Top)

    0.5mL K2 EDTA (Pink Top) or 6mL K2 EDTA (Pink Top) or 4mL K2 EDTA (Purple Top)

  • Minimum Volume Adult:

    1mL

    1mL

  • Minimum Volume Paediatric:

    0.5mL

    0.5mL

  • Sample Stability:

    Short term storage: 24 hours at Room Temperature. Long term storage: 7 days at 4-6

    Short term storage: 24 hours at Room Temperature. Long term storage: 7 days at 4-6

  • 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...

    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.

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  • Add On Test:

    Differential DAT ELUATE

    All urgent add ons via telephone must be confirmed via email to the appropriate email address

    RVIadditions.Laboratory@nuth.nhs.uk (internal)

    tnu-tr.bloodsciencesadditions@nhs...

    Differential DAT ELUATE

    All urgent add ons via telephone must be confirmed via email to the appropriate email address

    RVIadditions.Laboratory@nuth.nhs.uk (internal)

    tnu-tr.bloodsciencesadditions@nhs.net (external)

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  • Interpretation:

    A negative DAT suggests that no antibody is attached to the red blood cell and the signs and symptoms should be investigated for some other cause. A positive DAT suggests that there are antibodies ...

    A negative DAT suggests that no antibody is attached to the red blood cell and the signs and symptoms should be investigated for some other cause. A positive DAT suggests that there are antibodies attached to the red cell. The stronger the reaction the more positive the test the greater the amount of antibody is 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.

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  • Factors Affecting Result:

    Key factors affecting the result: • Samples which are old (>24 hours) • Incorrect specimen type received • Clotted, haemolysed, icteric or lipaemic samples • Insufficient plasma provided • Clotted ...

    Key factors affecting the result: • Samples which are old (>24 hours) • Incorrect specimen type received • Clotted, haemolysed, icteric or lipaemic samples • Insufficient plasma provided • Clotted samples may interfere with instrument pipetting and must not be used. • Fibrin or particulate matter, clots, bubbles or scratches can interfere with reaction interpretations.

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  • Referenced Documents:

    4/1/15

    4/1/15

  • Routine Contact Name:

    Section Leader:

  • Routine Telephone:

    Freeman: 0191 213 7849
    RVI: 0191 282 43435

    Freeman: 0191 213 7849
    RVI: 0191 282 43435

  • Specialist Test:

    Yes

    Yes

  • Specialist Contact Name:

    transfusion manager

    transfusion manager

  • Specialist Telephone:

    0192 213 9169

    0192 213 9169

Availability:

All times.

Turn Around:

4 hours

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