The computer crossmatch: a safe alternative to the serological crossmatch

The crossmatch has evolved from including a wide range of techniques through a test purely to eliminate ABO incompatibility (immediate spin) to computer crossmatching in which no serological testing is carried out and validation ensures the correct ABO/RhD type blood is issued. The crossmatch was always considered to be the most important feature of the compatibility test and in particular the antiglobulin phase; however, there are potential risks associated with serological and computer crossmatching including technical and procedural errors. The use of immediate spin and computer crossmatch change the emphasis for safety of the compatibility test from the crossmatch to the antibody screen. UK guidelines have now been published describing the features necessary for the introduction of computer crossmatching. Computer crossmatching is used by many institutions in various countries. It is considered safe practice and brings benefits to the laboratory and the patient. Compatibility testing is only one element of the blood transfusion procedure; the others are equally as important and include correct patient identification at the time of collection of the blood sample and at the administration of the blood transfusion.     

TRALI: correlation of antigen-antibody and monocyte activation in donor-recipient pairs

BACKGROUND: TRALI may be a severe reaction associated with transfusion of plasma-containing blood components. TRALI has usually been associated with antibodies against granulocytes and HLA class I antigens, but more recently with antibodies against HLA class II and monocytes. TRALI cases were investigated to determine correlation between antigen and antibody. Additionally, activation of monocytes by TRALI serums was studied. STUDY DESIGN AND METHODS: Sixteen cases of TRALI were investigated. All patients were typed for HLA antigens. Implicated donors were screened for HLA antigens and antibodies against granulocytes and monocytes. In 6 cases, recipient monocyte activation was measured in vitro after incubation with TRALI and control serums. In four cases, monocyte activation was measured after incubation of TRALI serums against a panel of monocytes of known HLA antigen type. RESULTS: In 14 of the 16 cases (87.5%), antigen-antibody correlation was identified. TRALI monocytes, incubated with implicated TRALI serum (n = 6), expressed significantly greater cytokine and tissue factor (p < 0.05, repeated-measures ANOVA) than controls. Panel monocytes incubated with TRALI serum showed increased expression of cytokine and/or tissue factor when corresponding antigen was present. CONCLUSION: In most cases of TRALI, a correlation between antigen and antibody can be identified. Activation of monocytes and their subsequent release of cytokines may play a role in the pathogenesis of TRALI.     

The sensitivity and specificity of the immediate-spin crossmatch

The immediate-spin (IS) crossmatch is used to detect ABO incompatibility between donor red cells (RBCs) and the serum of the intended recipient. However, this test may be positive in the absence of ABO incompatibility (false positive) or it may be negative when ABO incompatibility exists (false negative). During a 25-month study, the rates of both false-positive and false-negative IS crossmatch results were evaluated, and the sensitivity and specificity of the IS crossmatch were determined. During the study period, 53,656 IS crossmatches were performed for patients without significant RBC antibodies. Fifty-five patients had positive IS crossmatches, and no false-negative reactions were found. In tests of 55 patients with positive IS crossmatches, 77 false-positive and 5 true-positive reactions were noted. The causes of the false-positive reactions were rouleaux (36 patients), cold-reactive antibodies (8 patients), a combination of rouleaux and cold-reactive antibodies (2 patients), fibrin clot (1 patient), and undetermined (3 patients). The sensitivity and specificity of the IS crossmatch were 100 and 99.86 percent, respectively. Laboratory personnel should be aware that the IS crossmatch may have false-positive or false-negative results, and they should develop written protocols to distinguish quickly between true-positive and false-positive reactions.     

The difficult crossmatch: a consideration of the staff and not the method

The crossmatching laboratory is regarded as a stressful work environment where many nontechnical issues may influence the interpretation of test results, particularly if the results are unclear. An attempt has been made to identify major areas of conflict and stress and to demonstrate their relationship to the quality of crossmatching. The Janis an Mann model for decision making in conflict situations is presented and related to interpretation of crossmatches.     

Role of the crossmatch in testing for serologic incompatibility

Nine unexpected antibodies of unquestioned clinical significance were detected when the major crossmatch was performed on 31,320 pretransfusion blood samples from 8969 patients whose screening test for unexpected antibodies was nonreactive. Three of the antibodies retrospectively were found to manifest a positive screening test. Another antibody was not detected by the antibody screening test due to an error in preparation of the screening red blood cells. The overriding importance of the major crossmatch is the assurance of ABO compatibility between donor blood and recipient. Therefore, while this study does not resolve whether the antiglobulin phase of the procedure might be considered optional, the major crossmatch should not be eliminated.     

Evidence-based practice: compatibility with nursing

This article explores the compatibility of evidence-based practice with nursing. The generation of relevant research evidence in nursing and determining best evidence are discussed. The article concludes that different forms of research, other than randomised controlled trials, are valid and in many cases more applicable to nursing practice, and that nurses need to determine what constitutes relevant and best evidence for the profession.     

Is a room-temperature crossmatch necessary for the detection of ABO errors?

The detection of anti-A and anti-B isohemagglutinins by low-ionic- strength saline tests at 37 degrees C and by the indirect antiglobulin technique, without an "immediate'spin" or room-temperature phase, has been studied. Using such a procedure, all but one of 2746 patient blood samples reacted in accordance with ABO type when tested against A2 and B red cells. However, the discrepant sample also was nonreactive when tested by "immediate-spin" technique against saline-suspended A2 red cells. Our findings indicate that compatibility tests performed at 37 degrees C in low-ionic-strength saline are as sensitive as "immediate- spin" tests with saline-suspended red cells for the detection of ABO errors. Performing serologic tests for unexpected alloantibodies and donor-recipient compatibility without an "immediate-spin" or room- temperature phase abbreviates pretransfusion testing and reduces the detection of clinically insignificant alloantibodies solely reactive at room temperature.     

The risk of abbreviating the major crossmatch in urgent or massive transfusion

The risk of abbreviating the major crossmatch in urgent situations by issuing blood after an "immediate spin" phase was evaluated by a retrospective study of 82,647 crossmatches performed on serum from approximately 13,950 patients. Although the initial screening test for unexpected antibodies for all patients failed to show agglutination or hemolysis of the reagent red blood cells, agglutination was subsequently noted during at least one crossmatch performed for 148 of them. Further evaluation of these patients' serums indicated that most positive reactions were due to weakly reactive low thermal amplitude antibodies. Eight of the incompatible crossmatches were related to antibodies in the Kell, Kidd or Rh systems, and a ninth antibody, anti- E, was identified through subsequent evaluation of a cold antibody- induced crossmatch incompatibility. Issuance of blood in urgent situations after an "immediate spin" phase of the crossmatch, for patients whose red blood cells have been typed, and whose serums have been screened for unexpected antibodies, has a low level of risk.