Anti-A and anti-A,B monoclonal antisera with high titers favor the detection of A weak phenotypes.

Objectives: This study aimed to evaluate the reactivity and the titers of commercial anti-A and anti-A,B antisera in the detection of A weak antigen expression in human red blood cells.

Background: Commercial monoclonal antisera for ABO phenotyping are useful reagents allowing the identification of the four main ABO phenotypes (A, B, AB, and O). However, the reactivity of these commercial reagents can not be evident when the A or B antigens are weakly expressed, and these antisera have low titers.

Methods/materials: Six samples from blood donors and five samples from patients with ABO forward and reverse discrepant phenotyping were evaluated. The ABO phenotyping was carried out with different commercial monoclonal anti-A and anti-A,B antisera under different temperatures, using test tubes and gel column agglutination.

Results: Monoclonal anti-A antisera with titers less than 256 and anti-A,B with titers less than 128 failed to detect the weak expression of A antigen in 73% and 67% of the A weak phenotypes, respectively. Titres equal to or higher than 2048 (anti-A) and 1024 (anti-A,B) showed better reactivity, independent of the cell clone.

Conclusion: Our data indicate that anti-A and anti-A,B antisera with high titers give better reactivity with red blood cells carrying A weak antigen expression.