Weak and partial D phenotyping: a comparison study between molecular and serologic results.

Area of Science:

• Transfusion Medicine
• Immunology
• Genetics

Background:

• Variant D antigens can lead to inconsistent serologic test results when using Anti-D reagents.
• Limited data exists on the capacity of Anti-D reagents to distinguish D variants identified through RHD genotyping.

Purpose of the Study:

• To evaluate the ability of 20 U.S. Food and Drug Administration-licensed Anti-D reagents to identify molecularly defined D variants.
• To determine if reactivity patterns can correlate with specific D variants.

Main Methods:

• Tested red blood cells from 119 donors with variant RHD alleles using 20 Anti-D reagents.
• Utilized immediate spin (IS) and indirect antiglobulin test (IAT) with conventional test tube and column agglutination technologies.
• Analyzed agglutination reaction strength to correlate reactivity with specific D variants.

Main Results:

• Immediate spin (IS) showed more negative or weak reactions, while the indirect antiglobulin test (IAT) yielded more positive reactions (3+/4+ agglutination).
• RHD*01W.3 samples exhibited the strongest reactivity at both IS and IAT.
• RHD*01W.2 samples displayed the greatest variation in reactivity, with the weakest overall reactivity at IS. All weak D types had samples yielding both negative and 4+ agglutination results at IS.

Conclusions:

• Serologic testing alone, even with multiple Anti-D reagents, is insufficient to definitively identify weak or partial D types.
• The study highlights the necessity of molecular testing for accurate D variant characterization and risk assessment for alloanti-D.
• Multiple Anti-D reagents can help identify samples requiring reflex molecular testing.