RESUMEN
The 19-year-old twin sisters donated their blood in 2000. Their blood had typical Rh D negative red cell phenotype in Rh typing and weak D test using an anti-D reagent (Dade Behring, USA). Twin sisters donated blood again in 2001. Both were negative in anti-D reagent (Bioscotte Ltd., UK) and weakly positive in additively performed weak-D test. So we have acquired blood samples from them for further study in 2002. The red blood cells from twin sisters were not agglutinated with 4 various commercially available anti-D reagents. But in subsequently performed weak-D test, different reactivity to their anti-D reagents were shown, namely negative (Dade Behring, USA) and weakly positive (Ortho-clinical diagnostics, USA; Greencross, Korea; Bioscotte Ltd., UK). The lack of reactivity with some anti-D as shown in these cases can indicate the presence of a partial D antigen. So we carried out a additional serologic test using 6 monoclonal anti-D antibodies in partial-D typing set (Diamed, Switzerland) on Rh D antigens of red cells from twin sisters. According to the different reactivity patterns, we confirmed elder sister was partial-D category DFR and younger sister was partial-D with indeterminate category.