The importance of antibodies against low‐incidence RBC antigens in complete and abbreviated cross‐matching

BACKGROUND: It is common practice to perform an antiglobulin cross-match only when unexpected RBC alloantibodies are present, to detect antibodies against additional RBC antigens. In this study, the incidence of unexpected antibodies to low-incidence antigens (Ab-LIA) over a period of 23 years was investigated. STUDY DESIGN AND METHODS: Records of RBC antibodies and the accompanying transfusion history from 1978 through 2000 was retrospectively examined. Complete cross-matches were performed for all RBC transfusions before 1991. As of 1991, the type-and-screen policy was applied. To study the incidence of anti-Wra, a prospective study was conducted on sera from 462 patients sent to the transfusion laboratory and 486 blood donors. RESULTS: The records of 1795 patients containing 2257 RBC antibodies were examined. In 89 patients, a total of 94 Ab-LIAs was found. Anti-Wra was the most frequently encountered Ab-LIA. Thirty-nine patients had Ab-LIA in combination with other antibodies, 20 of which were autoantibodies. Eighty percent of these Ab-LIA were found at the first positive antibody screening test. Fifty-one solitary Ab-LIA were found in 50 patients, 37 during antibody screening tests, and 14 after positive complete cross-matches conducted before 1991. After an RBC antibody was detected, 664 patients received a total of 7792 RBC transfusions. Since the introduction of the type-and-screen policy, only one anti-Wra has been discovered during complete cross-matching. No transfusion reactions due to Ab-LIA were reported during the study period. In the prospective study, 12.3 percent of patients and 4.3 percent of blood donors had anti-Wra. CONCLUSIONS: Although Ab-LIAs are found coincidentally in the sera of only 2 to 3 percent of patients with other RBC antibodies, they are formed often. Because we found no difference in serologic incompatibility, due to Ab-LIAs, between patients with and without other blood group antibodies, we conclude that blood can be transfused safely to patients without performing a complete cross-match.