Report on anti-Di^b encountered in two Hong Kong Chinese

Two cases of anti-Di^b, a rarely encountered antibody, were identified in serum samples referred by hospital blood banks during the past 13 months. Case 1 is a 4l-year-old female who required blood for elective surgery. Case 2 is a premature infant suffering from mild neonatal jaundice on day 2 after birth. The anti-Di^b in both cases exhibited marked dosage effect. The titer/score against Di(a+b+) and Di(a-b+) red blood cells (RBCs) in case 1 was 8/10 and 32/32, respectively, and in case 2, 4/18 and 32/46. The monocyte monolayer assay (MMA) also gave a similar pattern of results, being l5 percent and 100 percent reactive when tested with Di(a+b+) and Di(a-b+) RBCs in case 1, and 0.4 percent (within normal range) and l4.4 percent in case 2. The patient in case 1 underwent her operation without blood transfusion. The infant in case 2 was treated by phototherapy and subsequently recovered without the need for exchange transfusion. Immunohematology 1997;13:17–19.