Diego(a) antigen frequency and anti-Diego(a) frequency in a South Texas community

The objective of this study was to determine the percent of the donor population in a South Texas community positive for the red cell antigen Diego(a) (Di(a)) and to determine the percent of anti-Di(a) in previously transfused patients.

Donor segments from 270 type A and type O donors were typed with anti-Di(a) and 305 previously transfused patients were screened for anti-Di(a).

The study was conducted using donor segments from units collected by the South Texas Blood Center and blood samples from patients in three hospitals in Corpus Christi TX.

The typing serum was from a type A donor, so only A and O donors were used for the antigen typing. The sera used for the antibody screens were from patients with previous transfusions in the local hospitals. Duplicate samples were eliminated.

Of the 270 type A and O donors, seven (2.6%) were found to be Di(a) positive and four (1.3%) of the 305 previously transfused patients had anti-Di(a).

In 1985, red blood cell antigen typing of Mexican American blood donors in the Corpus Christi area revealed a Di(a) antigen frequency of 14.7% with eight percent in Mexican American blood donors from two other areas of Texas. With an Hispanic population of 50.4%, it was expected that four percent to seven percent of the donor population would be positive for the antigen. The finding of only 2.6% Di(a) positive donors demonstrates about a 20% Mexican American donor population. Anti-Di(a) was found in 1.3% of the plasma samples from previously transfused patients. These results would indicate a 0.03% to 0.05% transfusion incompatibility in patients with a negative antibody screen for the Corpus Christi area. Areas of the United States with a higher percent Mexican American donor population would expect a higher percent incompatibility. Since the Mexican American population is increasing in South Texas and several other areas in the United States, the antibody may become increasingly important in transfusion therapy and as a cause of hemolytic disease of the newborn.