DAT positivity in blood donors: a perplexing scenario

Area of Science:

• Transfusion Medicine
• Immunology
• Hematology

Background:

• A blood request was made for a 70-year-old male patient with Chronic Obstructive Pulmonary Disease and anemia.
• One unit of blood was found incompatible during the antihuman globulin (AHG) phase of testing.

Observation:

• The patient's antibody screen, indirect antiglobulin test (IAT), direct antiglobulin test (DAT), and auto-control were all negative.
• The donor unit's DAT was positive using an anti-IgG gel card but negative with C3d reagent, and the donor's auto-control was positive.

Findings:

• The donor unit exhibited a positive DAT, indicating the presence of antibodies coating the red blood cells.
• The positivity was specifically associated with IgG antibodies, as confirmed by the anti-IgG gel card.

Implications:

• Positive DAT results in donor units necessitate deferral, notification, and physician referral.
• Further studies are required to understand the clinical significance and management of such cases in blood transfusion services.