Unexpected Red Cell Antibodies Research Articles

Sensitivity of column agglutination technology in detecting unexpected red cell antibodies

Summary. This study was conducted to compare a new microtube column agglutination technology (CAT) with a previously described tube saline‐indirect antiglobulin test (SIAT) with carefully defined performance in the detection of unexpected antibodies. On testing 117 sera from fresh and frozen stock containing antibodies detectable by SIAT, CAT failed to detect two examples of weak anti‐K. All other discrepancies between the two techniques involved antibodies generally regarded as clinically insignificant. Titration studies with anti‐D (concentration approximately 10 ng/ml) and 23 other antibodies, and studies with 10 weak antibodies of various blood group systems, showed the two techniques to be of similar sensitivity. Equivocal CAT results requiring repeated testing were found in 4·1% of specimens tested. We conclude that the CAT method adequately meets our requirements in sensitivity of detection of unexpected antibodies in pre‐transfusion testing and offers opportunities for savings in technical staff time.

The routine use of soluble Lewis antigens in the identification of Lewis system antibodies.

Approximately 3 percent of the blood samples tested at the authors' laboratory have contained unexpected red cell (RBC) antibodies, of which about one-third have been anti-Le(a) or anti-Le(b). Although these antibodies are usually clinically insignificant, considerable workload was expended in their identification. In hopes of reducing this workload, an alternative approach for identifying these antibodies was implemented. If a patient had no history of unexpected antibodies, with the exception of Lewis system antibodies, and if the results of serum antibody detection testing were typical for the presence of anti-Le(a) and/or anti-Le(b), the serum was treated with commercially standardized soluble human Le(a) and Le(b) blood group substances, and the Lewis phenotype of the patient's red cells was determined. If the treated serum demonstrated specific antibody neutralization and the red cell phenotype was Le(a-b-), the results were interpreted as positive for anti-Le(a) or anti-Le(b), and no further antibody identification workup was performed. If the patient was Le(a+b-) or Le(a-b+), or if the treated serum failed to demonstrate specific antibody neutralization, the serum was tested against panels of reagent RBCs that were licensed for the identification of unexpected antibodies. During the study period (8-1-89 to 6-16-90), 498 of 46,965 patients' samples met the criteria for testing for specific antibody neutralization. Of these 498 blood samples, 452 showed specific neutralization of antibody activity by Lewis substance and were Le(a-b-). Only 1 of these samples was discovered to contain an additional non-Lewis antibody (anti-Bg).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum Volumes Should Not Be Reduced When Testing Neonates for Unexpected Red Cell Antibodies

Serum-to-red cell ratio (volume:volume) significantly affects the sensitivity of antibody detection. Obtaining sufficient serum quantity can be a problem when testing blood from transported neonates not accompanied by maternal samples. Reducing serum volumes used for testing might result in missed antibodies. The authors studied 1,177 sera for unexpected red cell antibodies by comparing one versus two drops of patient serum using a technique with LISS at 37 degrees C through the antiglobulin phase. The serum-to-red cell ratio using two drops was approximately 50: 1. Results of 60% (58/96) of samples containing antibody benefited by the use of increased serum. Eighteen percent; (17/96) had antibodies detected only with two drops that were missed entirely by one, and 43% (41/96) showed stronger positive reactions using two drops versus one. Importantly, antibodies detected only with or enhanced by two drops were clinically significant (anti-D, anti-K, anti-M, anti-c, anti-E). Thus, reducing serum-to-cell ratio is potentially dangerous, and blood banks should insist on adequate sample size to ensure patient safety.

Experience With a Cost-effective Crossmatch Protocol

Pretransfusion blood samples were routinely tested for ABO group, Rh type, and the presence of unexpected red blood cell antibodies. Patients who had unexpected red blood cell antibodies received transfusions of blood that was crossmatched using an immediate spin test, a 37 degrees C incubation step, and an indirect antiglobulin test. Patients who did not have unexpected red blood cell antibodies received transfusions with blood that was crossmatched by an immediate spin crossmatch only. Because the average immediate spin crossmatch required only 3.25 minutes to be performed, crossmatches were not done for patients without unexpected antibodies until blood was actually requested to be issued for transfusion. During the first 8 1/2 months this protocol was used, 27,742 crossmatches were performed and 46,959 unnecessary crossmatches were avoided, thus reducing direct costs by at least +49,300. This protocol also allowed for optimal blood inventory control and minimized the outdating of units of blood to only 0.19%.