Blocked D phenomenon and relevance of maternal serologic testing

A blood requisition for double-volume exchange transfusion was received for a 2-day-old male child born to a 29-year-old multiparous female (P₂₀₀₂) referred to our institute having neonatal jaundice with encephalopathy; no maternal sample was received. The neonatal blood sample was typed as group A, D–, and the direct antiglobulin test (DAT) was strongly positive (4+) using the gel method. Mono-specific DAT showed the presence of IgG antibodies on neonatal red blood cells (RBCs). Acid elution and gentle heat elution (at 56°C) confirmed the presence of anti-D on neonatal RBCs. The baby received two exchange transfusions with group O, D–, packed RBCs compatible with his own serum. Later, on day 3, the neonate’s mother was typed as group AB, D–, and her serum revealed the presence of alloanti-D, -C, and -S reactive in the anti-human globulin phase. The anti-D titer was 1024. This report highlights the “blocking” phenomenon caused by maternal anti-D in a case of hemolytic disease of fetus and newborn with a positive DAT. Immunohematology2015;31:116–118.