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Direct Antiglobulin Test - Provincial

Discipline

Transfusion Medicine

Overview

Description

  • The Direct Antiglobulin test (DAT) is used to determine if red cells have been coated in vivo with IgG immunoglobulin, complement (C3d), or both.

Alias

  • Coombs test
  • DAT
  • Direct Coombs

Specimen Information

Specimen types accepted

  • Whole blood

Specimen collection container

Required volume

  • Optimal volume: 4 mL
  • Minimum volume: 1 mL
  • Capillary volume (microcontainer EDTA only): 0.5 mL

Submitting the minimum volume makes it impossible to repeat the test or perform confirmatory/reflex testing. In some situations, a minimum volume may require a second collection.

Transport and stability

  • Store at 2-8°C.
  • Specimen stability varies depending on methodology (24 – 72 hours). Refer to local laboratory policies to determine specimen stability.

Rejection criteria

Testing Information

Relevant clinical history

  • Diagnosis
  • Recent transfusion and pregnancy history
  • History of hematopoietic progenitor cell or organ transplantation

Clinical interpretation

  • Negative – no IgG or complement (C3d) detected on the surface of the red cell.
  • Positive – IgG and/or complement (C3d) is present on the surface of the red cell. 
  • For neonates the Direct Antiglobulin Test (DAT) results do not always correlate with symptoms of clinical jaundice.

Performance

Methodology

  • Gel testing or tube testing.

Days/times performed

  • Complex sites (RUH and RGH): testing available 24 hours/7 days a week. 
  • Advanced sites: testing available; hours variable. 
  • Basic sites: testing available; hours variable.
  • Current State Blood Drop Map

Maximum laboratory time

  • Routine:
    • Complex sites and Advanced sites: within 24 hours of receipt in Transfusion Medicine.
    • Basic sites: within 48 hours of receipt in Transfusion Medicine.
  • Urgent:
    • Within 4 hours of receipt in Transfusion Medicine.
  • STAT:
    • Within 1 hour of receipt in Transfusion Medicine.

Specimen retention time

  • 5 weeks

Other information

Reflex Testing
  • Positive results (excluding newborns and neonates) will be tested with individual monoclonal reagents to determine if red cells are sensitized with C3d (complement),   Immunoglobulin (IgG), or both.
Additional Comments
  • Do not centrifuge
Forms Required
Relevant Recent Medication History
  • Recent medication history (the Medication Administration Record – MAR may be requested from patient care units by phone, if required).

Last Updated: June 12, 2024