RBC antibody persistence.

BACKGROUND: A person exposed to foreign blood group antigens may produce antibodies. The persistence of antibodies varies among people and among antibodies. A study was performed to investigate the persistence of clinically significant RBC alloantibodies over a period of 20 years. STUDY DESIGN AND METHODS: A retrospective examination was performed of all records of RBC antibodies in the transfusion laboratory computer database from 1978 through 1997. Records of patients who underwent at least one antibody investigation after an antibody had been detected were studied. The study included all antibodies against the Rh, K, Fy, Jk, and MNs blood group systems. An antibody was regarded as not persistent if, after previous detection, the screening or panel studies became negative for the antibody under study. Anti-D due to RhIg administration was excluded. RESULTS: An analysis was performed of 480 records consisting of 593 antibodies that fulfilled the criteria. Median antibody follow-up was 10 months (range, 1-240). In 137 patients, 153 (26%) antibodies became undetectable over the course of time. After initial negative screening investigations, 310 antibodies were formed. The antibodies that were still detectable had a median follow-up of 7 months (range, 1-193). A patient's age, sex, and antibody specificity were of no influence on the length of time that antibodies were detectable. Antibodies detected with a more sensitive screening technique were less persistent (p = 0.0002). For 28 patients, detection of antibodies was highly irregular. CONCLUSIONS: About 25 percent of all antibodies became undetectable over the course of time. The antibody screening technique used, rather than the antibody specificity, affected these results. To prevent delayed hemolytic transfusion reactions, precise antibody documentation is of great importance.

Alloimmunization after blood transfusion in patients with hematologic and oncologic diseases.

BACKGROUND: Because of intensive marrow depression and improved survival, patients with hematologic and oncologic malignancies are dependent on transfusion for a longer period. It has been advocated that these patients should receive blood that is matched for blood group antigens other than ABO and D. A retrospective study was performed on the rate of alloimmunization against red cell antigens in 564 patients with malignant hematologic diseases over a period of 10 years. STUDY DESIGN AND METHODS: Records of transfusion and immunohematologic studies of all patients (n = 1066) with malignant myeloproliferative and lymphoproliferative diseases diagnosed between 1987 and 1996 at one hospital were collected from the hospital computer blood bank files. Transfusions were correlated with antibody formation. Factors affecting this correlation were analyzed. RESULTS: Seventy-one antibodies were found in 51 patients. The overall immunization rate was 9.0 percent. Fifty percent of antibodies were formed after 13 units had been transfused. Once a patient had formed an antibody, the probability of additional antibodies increased 3.3-fold. Anti-c, anti-E, and anti-K composed the majority of antibodies found. Four patients formed Rh system antibodies after incompatible platelet transfusions. Patients who underwent intensive chemotherapy formed antibodies at a much lower rate than other patients. More than 40 percent of antibodies became undetectable after the first detection. No difficulty was encountered in finding compatible blood for these patients. CONCLUSIONS: Antibody formation in hematologic malignancies is comparable to that in other diseases requiring multiple blood transfusions. Extensive antigen matching before transfusion of patients with hematologic and oncologic malignancies is not necessary and leads to increased costs.