Anti-A Titre Test – Serum
Overview:
The Anti-A titre test measures the amount (titre) of anti-A antibodies present in an individual’s serum. This test is particularly important in the context of blood transfusion compatibility, organ transplantation, and maternal-fetal blood group incompatibility.

Anti-A antibodies are naturally occurring in people who lack A antigens on their red blood cells—primarily individuals with blood group B or O.

Sample Type:
Serum (blood sample)

A blood sample is drawn, serum is separated, and the level of anti-A antibodies is determined through serial dilution and agglutination methods.

Purpose of the Test:
To determine antibody titre levels in individuals with blood group B or O

To assess risk of hemolytic transfusion reaction before giving incompatible blood

Evaluate hemolytic disease of the newborn (HDN) risk when there is ABO incompatibility between mother and fetus

Used in organ transplantation, especially for ABO-incompatible kidney or liver transplants, to guide desensitization protocols

How the Test Works:
The patient’s serum is mixed with type A red blood cells in varying dilutions

The highest dilution at which agglutination (clumping) occurs is recorded as the titre value

A higher titre means more anti-A antibodies are present

Interpretation of Results:
Low titre: Low level of anti-A antibodies; lower risk of immune reaction

High titre: High concentration of anti-A antibodies; may pose risk in transfusion or transplantation scenarios

In pregnancy, high maternal anti-A titres may increase the risk of ABO hemolytic disease of the newborn

Note: Normal titres vary depending on lab protocols, population, and purpose of testing.

Clinical Significance:
Helps prevent transfusion reactions

Guides organ transplant compatibility decisions

Assists in maternal-fetal monitoring in ABO-incompatible pregnancies

Supports safe cross-matching practices in blood banks

Limitations:
Titre levels may fluctuate over time or after exposure to antigens (e.g., transfusion, pregnancy)

Must be interpreted along with clinical history and blood group typing

Does not assess Rh antibodies (separate testing required for Rh incompatibility)

Conclusion:
The Anti-A Titre test is a valuable tool in transfusion medicine, transplantation, and maternal-fetal care. By quantifying anti-A antibodies in serum, it helps ensure compatibility, prevent immune complications, and guide treatment decisions in sensitive clinical settings.