ABO Compatibility Guidelines for O‑Positive Liver Transplant Recipients

Standard ABO‑Compatible Donors

• O‑positive liver transplant recipients should receive grafts from O‑positive (identical) or O‑negative (compatible) donors, which represent the safest and most straightforward options. 1
• The prevailing practice is to allocate ABO‑identical donors to ABO‑identical recipients whenever possible. 1

Expanded Donor Pool: A2 Subgroup

• A2 blood‑group donors can be used safely for O‑positive recipients, providing an important means to expand the donor pool. 1
• Because A2 donors express lower levels of A antigens, they do not trigger hyper‑acute rejection in O‑positive recipients. 1

Donor Blood Groups to Avoid (Contra‑indicated)

• A1 donors are contraindicated for O‑positive recipients due to higher antigen expression that leads to incompatibility. 1
• AB donors are also contraindicated for O‑positive recipients because of full ABO incompatibility. 1

Rh Factor Considerations

• The recipient’s Rh‑positive status does not limit liver transplantation; Rh antigens are not expressed on hepatocytes, allowing grafts from both Rh‑positive and Rh‑negative donors. 1

Clinical Decision Algorithm (Routine Practice)

• Prioritize O‑positive or O‑negative donors for routine transplantation of O‑positive recipients. 1

Experimental/High‑Risk Situations

• ABO‑incompatible grafts (beyond the A2‑to‑O option) are considered experimental and should be reserved for urgent cases where no compatible graft is available. 1