Comparative analysis of serological reactivity in genetically confirmed Rh variants within a recipient population

Detecting Rh variants in transfusion recipients is essential to prevent alloimmunization. This study compared the serological reactivity of various monoclonal antibodies using two techniques (gel column agglutination and microplate technology at room temperature) in relation to genetically confirmed Rh variants.

Over an 18-month period, all EDTA blood samples referred to the molecular laboratory were analysed. RHD and RHCE genotyping was performed, and samples carrying at least one variant allele underwent serological testing. Statistical analysis was performed using the McNemar test (p < 0.05).

Among 610 samples, 118 (19%) carried at least one Rh variant. The most frequent alleles were RHCE*CeRN (n = 39) and RHD*weak D type 1 (n = 14). Weak RhD (types 1 and 3) and partial RhD from RHD*DAR were serologically weakened (<4+) with both methods. Homozygosity for RHCE*CeRN was suggested by serological weakening of RH5 with both methods, whereas heterozygosity was indicated by serological weakening of RH2 with microplate only. Other variants with a few samples (RH1 of RHD*weak D type 2 and 5, RH2 of RHD*RHD-CE (4-7)-D, RH3 of RHCE*cEIV, RH4 of RHCE*ceJAL and RH5 of RHCE*ceMO.01 and RHCE*ceAR) showed weak serological intensities but lacked statistical confirmation. Finally, 39% of Rh variants were not detected as serologically weakened by both serological methods.

Phenotyping remains the first-line screening tool. Weak serological intensities help guide molecular investigations. However, detection of Rh variants using serology alone is highly variable. Combining different clones and techniques improves sensitivity.