The evaluation of a positive direct antiglobulin test in pretransfusion testing

The results of serologic studies on 879 blood samples with a positive direct antiglobulin test (DAT) are presented. All blood samples were from patients who were either anemic, for reasons other than blood loss, recently transfused, or had serum antibodies detected during routine pretransfusion tests. Blood samples from only 81 of the patients included in this study had serologically reactive eluates (64 autoantibodies, three antibodies to penicillin and cephalothin treated red blood cells, three passively acquired anti-A antibodies, and 11 transfusion-induced alloantibodies). The eluted antibodies were also detected in the serum by routine pretransfusion tests in 13 of the patients whose red blood cells eluted autoantibodies, and in five of the patients whose red blood cells eluted transfusion-induced alloantibodies. All but one of the 11 transfusion-induced alloantibodies were detected within 14 days posttransfusion. Based on these findings, a cost-effective and safe approach to the management of blood samples with a positive DAT would be to restrict the preparation and testing of eluates to those samples from recently transfused patients. It is the contention of the authors that the incorporation of the DAT in pretransfusion testing should primarily serve to detect alloantibody formation before such antibodies are evident in the serum, and should not be used to screen patients for unsuspected autoimmune hemolytic anemia. Furthermore, the authors question the necessity for blood banks to routinely perform an autocontrol on all blood samples from prospective transfusion recipients.     

Delayed hemolytic episodes due to anti-M

We observed three cases in which anti-M, undetectable in pretransfusion serum, was responsible for accelerated hemolysis of crossmatch- compatible red blood cells 5 to 15 days after transfusion. In each case, the direct antiglobulin test, which had been negative on pretransfusion testing, was weakly positive on the posttransfusion sample. Anti-M was identified in both the serum and eluate from the posttransfusion sample in two cases. In the third, anti-M could be identified only in the posttransfusion serum. Hemolysis was mild, and was not clinically suspected in any of these three patients until blood was requested for further transfusion. In one of the cases, the antibody was undetectable within a few weeks after the hemolytic episode. Destruction of transfused red blood cells by newly synthesized alloantibodies, particularly those of the Kidd system, is a familiar phenomenon to blood bankers. It is apparent from these studies that anti-M also can behave in this fashion.     

The efficacy of performing red cell elution studies in the pretransfusion testing of patients with positive direct antiglobulin tests

In order to evaluate the efficacy of performing red cell elutions in pretransfusion testing, the serologic records of 638 patients with positive direct antiglobulin tests (DAT) were reviewed. These patients were identified by routine antibody screening procedures that included an autologous control. DAT results on the red cells of these patients showed 279 with IgG and C3d sensitization, 319 with IgG alone, and 40 with C3d sensitization alone. Of 638 patients' red cell eluates, 401 demonstrated no reactivity, 154 demonstrated panagglutination, and 60 demonstrated passively acquired anti-A,B. Only 23 of 638 patients had alloantibody sensitization of their red cells. Of the 23, 19 had serum antibody corresponding to the specificity of antibody detected in the eluate. Thus, only four of 638 (0.6%) eluates gave results unavailable by serum testing alone. This study indicates that routine eluate investigation provides little useful information in assuring compatibility. Serum antibody testing and careful review of the clinical and transfusion history constitute appropriate pretransfusion testing in patients with positive direct antiglobulin tests. Eluate testing should be restricted to cases in which immune hemolysis is suspected clinically.     

Frequency of delayed hemolytic transfusion reactions following antibody screening and immediate-spin crossmatching

In view of the continuing controversy regarding the use of immediate-spin crossmatch procedures in preparing blood for transfusion to patients in whom unexpected clinically significant antibodies have not been found by antibody screening by the indirect antiglobulin test (IAT), a review of 8 years' experience with such a policy was conducted. In that period, 54,725 units of packed red cells or whole blood were transfused to 10,146 patients. Four clinically overt delayed hemolytic transfusion reactions and 18 clinically silent delayed serologic transfusion reactions were found. In 3 of the 22 patients, the offending antibody(ies) were detectable in the pretransfusion serum by an enzyme IAT, but none was detectable by routine saline IAT against either a three-cell screening panel or the transfused cells. Thus, the incorporation of saline indirect antiglobulin crossmatch would not have prevented the delayed reactions. It can be concluded that the use of a saline indirect antiglobulin crossmatch offers no significant advantage over the current policy of using only immediate-spin crossmatch for those patients whose pretransfusion serum gives negative results in a three-cell screen using a saline IAT.     

Studies of antibodies in the sera of patients who have made red cell autoantibodies

BACKGROUND: In patients in whom autoantibodies of broad specificity (panagglutinins) are present in the serum, adsorption studies are often necessary to identify alloantibodies that are simultaneously present. STUDY DESIGN AND METHODS: Samples from 138 patients in whom the direct antiglobulin test was positive and antibody was present in the serum were studied. When antibody identification studies before or after initial adsorption suggested the presence of an alloantibody, additional alloadsorptions were performed. RESULTS: Among the samples from 138 patients, 71 contained only panagglutinating autoantibody, and another 19 contained either autoantibodies or alloantibodies that were not accompanied by panagglutinins. The remaining 48 samples contained both panagglutinins and a total of 62 antibodies that appeared to be alloimmune in nature. Alloadsorption with antigen-negative red cells showed that 29 (47%) of the apparent alloantibodies were in fact partially adsorbed autoantibodies that mimicked alloantibodies by their reactions. CONCLUSION: Initial autoadsorption often left unadsorbed alloantibodies and autoantibodies with mimicking specificities. Initial alloadsorption more often left only true alloantibodies unadsorbed. From the screening tests, it appeared that 43 percent of the 138 patients were alloimmunized. Recognition of the mimicking nature of the partially adsorbed autoantibodies found that the real incidence of alloimmunization in the patients was 23 percent. Recognition of this phenomenon considerably simplifies the selection of blood for transfusion to these patients.     

When should antibody screening tests be done for recently transfused patients?

The American Association of Blood Banks (AABB) requires that blood samples used for pretransfusion testing of recently transfused (or pregnant) patients must be obtained within 3 days of scheduled transfusions. This requirement, which became effective in July 1988, amended Standard G2.000 of the AABB, which previously required that pretransfusion testing must be done on blood samples obtained within 2 days of scheduled transfusions. The present study was designed to estimate the risk associated with adopting the amended version of Standard G2.000. Sixty patients who developed significant unexpected alloantibodies after transfusion were studied retrospectively. Thirteen of the 60 patients were found to have newly detectable antibodies within 83 hours of a sample reported to be negative for the new antibody. Had the amended version of Standard G2.000 been in effect, the detection of some of these antibodies might have been delayed up to 24 hours. It was estimated that the implementation of the new AABB requirement at the authors' institution could potentially place about 1 in 3000 transfused patients at risk for an acute or delayed hemolytic transfusion reaction.     

Hemolysis following intravenous immune globulin therapy

Two patients who had hemolysis after receiving large doses of intravenous immune serum globulin are reported. Both patients had positive direct antiglobulin tests due to alloantibodies contained in the immune serum globulin. Markedly increased red cell transfusion requirements and elevated serum bilirubin levels provided evidence of hemolysis.     

Revisiting the issue: can the reading for serologic reactivity following 37°C incubation be omitted?

BACKGROUND: Omitting the 37 degrees C reading from screening tests for unexpected antibodies results in failure to detect some Rh, K, and Jk agglutinins of potential significance (wanted positives). However, this measure avoids unwanted positive tests due to cold agglutinins. STUDY DESIGN AND METHODS: Using data from prior publications, actual risk calculations (ARCs) were made to predict the risk of eliminating the 37 degrees C reading, pretransfusion direct antiglobulin test (DAT), and routine indirect antiglobulin crossmatch (IAT-XM). ARCs used the equation: wanted positives missed x 0.34 (or 0.80) x 5 x percent antigen-positive, where 0.34 = percent of patients transfused (ARCs for 37 degrees C reading and DAT); 0.80 = percent of crossmatched patients transfused (ARCs for IAT-XM); 5 = average number of units transfused. Following elimination of the 37 degrees C reading, the impact of this change on patient care was monitored. Antibody detection and identification data and transfusion reaction reports for 6 months after the change were reviewed. Recently transfused patients with new antibodies were evaluated for immune hemolysis by review of clinical and laboratory data. The findings were compared with those from the same dates of the preceding year. RESULTS: The risk of transfusing incompatible blood by eliminating the DAT, IAT-XM, and 37 degrees C reading is approximately 1:13,000, 1:2,000, and 1:2,400 units transfused, respectively. The cumulative risk from eliminating all three tests is approximately. 1 :1,000 units. With respect to the 37 degrees C reading, there were no differences between the pre-change and post-change study periods in the incidence of reported transfusion reactions or cases of immune hemolysis associated with newly formed antibodies. However, unwanted positive tests decreased from 162 to 61 following elimination of the 37 degrees C reading. This represents a decrease of 20 percent in the number of samples requiring antibody identification annually. CONCLUSIONS: Eliminating the 37 degrees C reading from pretransfusion antibody screening tests imposes less risk than omitting the routine IAT-XM, and it avoids the time and costs of evaluating unwanted positive tests, thus reducing expenditures and delays in patient care.     

Comparison of a manual hexadimethrine bromide-antiglobulin test with saline- and albumin-antiglobulin tests for pretransfusion testing

A prospective double-blind study compared a manual hexadimethrine bromide (Polybrene) antiglobulin antibody detection test (P-AHG) and crossmatch with the albumin-antiglobulin antibody detection test and saline-antiglobulin crossmatch routinely used in our laboratory. A total of 10,084 pretransfusion blood samples from approximately 6000 patients were tested. The P-AHG method detected 153 of 157 alloantibodies for which antigen-negative, crossmatch-compatible blood is routinely provided. All four antibodies not detected were anti-K. The routine techniques detected 147 of the 157 alloantibodies. The P-AHG method detected only 36 percent of the alloantibodies for which crossmatch-compatible blood is routinely provided without determination of the antigen status of the donor unit's red cells (e.g., anti-Lea), whereas the routine method detected 91 percent of such antibodies. Eighty-six percent of the 189 alloantibodies detected by the Polybrene technique were found before the addition of antiglobulin. The manual Polybrene test is a rapid and sensitive technique; it may be used without an antiglobulin phase as a routine crossmatch procedure when accompanied by a sensitive antibody detection test that includes antiglobulin and an additional test to ensure ABO compatibility.     

Prophylactic antigen-matched donor blood for patients with warm autoantibodies: an algorithm for transfusion management

BACKGROUND: Patients with warm autoantibodies are at high risk for delayed hemolytic transfusion reactions due to the presence of alloantibodies. To provide blood safe for transfusion and to avoid adsorption studies in some cases, the provision of prophylactic antigen-matched donor blood where feasible for patients with warm autoantibodies is advocated. STUDY DESIGN AND METHODS: Twenty consecutive adult patients with warm autoantibodies (January 1999 to February 2000) received chronic RBC transfusions by use of this protocol: the serology consistent with warm autoantibodies was confirmed; the alloantibodies were identified; the complete phenotype was determined (i.e., C, E, c, e, K, Jk(a), Jk(b), Fy(a), Fy(b), S, and s); and prophylactic antigen-matched (i.e., donor RBCs matched with the patient's phenotype), WBC-reduced donor RBCs were provided for transfusion. On subsequent admissions, samples were evaluated by panel studies and DATs. If the serology remained consistent with previous findings, prophylactic antigen-matched, WBC-reduced RBCs were transfused without further testing. RESULTS: Eight of 20 (40%) patients had existing, clinically significant alloantibodies. In 12 of 20 (60%) patients, a phenotype was determined and the patients received transfusion of a total of 149 prophylactic antigen-matched RBC units (mean, 15 units per patient) precluding adsorption studies on 51 pretransfusion samples. In 8 of 20 (40%) cases (2 with alloantibodies), phenotypes were indeterminant, necessitating differential allogeneic adsorption studies on 39 samples before transfusion of 144 RBC units (mean, 18 units per patient). CONCLUSIONS: Determining complete phenotypes should be a routine component of the serologic evaluation of patients with warm autoantibodies. Our algorithm for providing prophylactic antigen-matched RBCs to these patients when a complete phenotype can be determined provides flexibility in their transfusion management while maintaining safety and circumvents or simplifies pretransfusion adsorption studies.     

Changes in peripheral blood CD5 (Bla) B-cell populations and autoantibodies following blood transfusion

BACKGROUND: CD5 B cells and the natural autoantibodies they produce play a role in antigen presentation, tolerance induction, and maintenance of an idiotypic immune network. The effects of transfusion on autoantibodies and peripheral blood CD5 B cells were studied. STUDY DESIGN AND METHODS: Eight previously transfused patients with sickle cell anemia and five patients who underwent orthopedic surgical procedures with transfusion were enrolled in the study. Patients in both groups received 1 to 2 units of allogeneic packed red cells. Ten untransfused healthy adults and five patients who underwent orthopedic surgery without transfusion were enrolled as controls. Peripheral blood CD5 B cells, serum levels of IgM, antinuclear antibodies, rheumatoid factor, and anticardiolipin IgM were quantitated either at the beginning of the study (baseline sample), before transfusion, or before surgery and either at 1-, 2-, 4-, 6-, and 8-week intervals after transfusion, after surgery, or after the baseline sample was obtained. RESULTS: IgM levels and the absolute number of B cells that coexpressed CD5 rose to twice pretransfusion levels in six of eight transfused sickle cell anemia patients and in four of five transfused orthopedic surgery patients. No comparable increases in CD5 B cells were noted in untransfused controls. Preexisting rheumatoid factor and antinuclear antibody levels increased in four of five transfused orthopedic surgery patients. One sickle cell anemia patient developed anti-Fya despite receiving Fya-negative blood. Increasing titers of anti-Fya paralleled the increases in IgM and CD5 B cells after transfusion. One patient who developed a positive direct antiglobulin test after transfusion had large increases in serum anticardiolipin IgM. Anticardiolipin IgM was subsequently eluted from direct antiglobulin test-positive red cells obtained after transfusion. Antibodies with anti-Fya-like activity and anticardiolipin IgM were produced in vitro by CD5 B cells and not by conventional CD5-negative B cells. CONCLUSION: An association was found between transfusion-induced increases in CD5 B cells and increased autoantibody production. These data may have implications for immunologic intervention to prevent the induction of red cell antibodies and other changes in the immune system caused by exposure to foreign antigens via blood transfusion.     

Prevalence of HLA antibodies in transfused patients with and without red cell antibodies

BACKGROUND: Multiply transfused patients are at increased risk of developing red cell (RBC) antibodies, as well as antibodies to HLA. Although pretransfusion testing screens for RBC antibodies, no such testing is routinely performed for HLA antibodies. Determining which patients are more likely to make HLA antibodies may be important for patients undergoing elective surgery where platelets (PLTs) may be required. It is hypothesized that patients with RBC alloantibodies may be more likely to have HLA antibodies than previously transfused patients without RBC antibodies. STUDY DESIGN AND METHODS: Blood was collected from 53 adult male surgical patients with RBC alloantibodies and a control group of 69 similar male patients with a history of previous transfusions but no evidence of RBC alloimmunization. The samples were tested for the presence of immunoglobulin G Class I HLA antibodies by enzyme-linked immunosorbent assay. RESULTS: Of the 53 samples from patients with RBC alloantibodies, 12 (22.6%) also had HLA antibodies, whereas only 7 (10.1%) of the 69 patients in the control group had HLA antibodies (p < 0.03). CONCLUSIONS: There is a significant difference between the rates of HLA alloimmunization in male patients with RBC antibodies versus multiply transfused patients without RBC antibodies. Screening for HLA antibodies may be warranted in patients with RBC alloantibodies who might require PLT transfusion support for elective surgery.     

Assessment of clinical significance of anti-Ge in an untransfused man

A 19-year-old, untransfused Melanesian man from Papua New Guinea was admitted to the hospital for repair of an atrial septal defect. His serum contained an alloantibody that reacted strongly on the indirect antiglobulin test and was identified as anti-Ge. Gerbich-negative blood was transfused following urgent surgery. A 51Cr red cell survival study performed 2 weeks after surgery yielded zero survival of Gerbich-positive cells after 24 hours. A monocyte-driven, antibody-dependent, cell-mediated cytotoxicity assay performed on both pretransfusion and posttransfusion serum samples and on concentrated serum showed less than 1 percent specific lysis of Gerbich-positive cells. This did not correlate with the indication of clinical significance predicted by the 51Cr study. Red cell adherence and phagocytosis, not evident in a monocyte monolayer assay using native serum, were demonstrable in 16 percent of monocytes by the use of concentrated serum.     

Lack of clinical significance of "enzyme-only" red cell alloantibodies

In a retrospective study on samples from 10,000 recently transfused patients, 35 samples were found to contain an antibody that reacted with ficin-treated red cells but was not demonstrable by low-ionic- strength saline solution and indirect antiglobulin test (LISS-IAT). In those 35 patients, the specificity of the antibody was such that each patient would have been transfused with antigen-negative blood had the antibody reacted in LISS-IAT. Tests on red cells from the units already transfused showed that 19 patients had among them received, by chance, 32 antigen-positive and 74 antigen-negative units. The remaining 16 patients had among them received 57 units that were, again by chance, all antigen negative. One patient given antigen-positive blood suffered a delayed transfusion reaction; in two others the antibodies became LISS-IAT active after transfusion. However, similar changes to the LISS- IAT-active state were seen with two antibodies of patients given only antigen-negative blood. Also found in the 10,000 patients were 28 clinically insignificant antibodies, 77 sera in which the antibody was too weak to identify, and 216 autoantibodies that reacted only with ficin-treated red cells. These data support a belief, generally held in the United States but not necessarily elsewhere, that the use of protease-treated red cells for routine pretransfusion tests creates far more work than the accrued benefits justify.     

Suitability of preadmission blood samples for pretransfusion testing in elective surgery

BACKGROUND: North American transfusion guidelines do not stipulate a time limit between drawing the specimen for pretransfusion testing and giving the transfusion to patients who have not received a transfusion or been pregnant in the preceding 3 months. British guidelines suggest that separated plasma and serum can be stored at -30 degrees C for up to 6 months, but they draw attention to the paucity of evidence concerning the use of stored samples. In Australia, transfusion guidelines recommend a maximum of 10 days' validity for pretransfusion specimens, which requires the patient to present for pretransfusion testing within 10 days of admission or to undergo retesting after admission, which in turn necessitates additional time in the hospital before operation. The study was performed to document the safety of using for pretransfusion testing a blood sample collected more than 10 days before surgery. STUDY DESIGN AND METHODS: Samples from 500 patients scheduled for elective surgery who had not been pregnant or received a transfusion in the previous 3 months were separately tested in blood group and antibody screens at an interval from 11 to 335 days before admission and again on admission. RESULTS: No clinically significant change was detected in the red cell antibody status of the paired samples of any patient. CONCLUSION: For patients who have not been transfused or pregnant in the previous 3 months, it is safe to crossmatch blood for transfusion by using a sample collected well in advance of elective surgery and stored at -30 degrees C.     

Detection of multiple passively acquired alloantibodies following infusions of IV Rh immune globulin

BACKGROUND: Passively acquired blood group alloantibodies are detected regularly after infusions of IV Rh immune globulin (RhIG) for the treatment of immune thrombocytopenic purpura (ITP) in D+ patients. STUDY DESIGN AND METHODS: Blood samples from 16 D+ patients with ITP were tested after treatment with IV RhIG for the presence of passively acquired alloantibodies. Similar studies were conducted for three D- patients after injections of IM RhIG for Rh immunoprophyl-axis. Four production lots of IV RhIG and 2 lots of IM RhIG were tested for the presence of alloantibodies. RESULTS: All 16 D+ patients with ITP developed a positive DAT, as well as positive antibody detection test results, after infusions of IV RhIG. All postinfusion plasma samples contained anti-D, as well as one or more additional antibodies, usually anti-C, -E, -G, -V, or -Fy(a). Eluates from patients' RBCs with positive DAT results contained multiple passively acquired alloantibodies. Multiple alloantibodies were detected in samples of different production lots of IV RhIG or IM RhIG. No acute transfusion reactions were observed in five D+ patients with ITP who had been treated with IV RhIG and had been given serologically incompatible D+ RBCs. After injections of IM RhIG, the only passively acquired alloantibody detected was anti-D. CONCLUSION: Plasma samples from D+ patients with ITP treated with IV RhIG regularly contained anti-D and multiple other passively acquired Rh, Duffy, or Kidd system alloantibodies. Postinfusion RBC samples all had positive DAT results with eluates containing anti-D and multiple other Rh, Duffy, or Kidd system antibodies. The consistent detection of multiple passively acquired alloantibodies after IV RhIG, in contrast to the detection of anti-D only after IM RhIG, reflects the immediate effect of the entire (bolus) dose of RhIG by the IV route, the dose for treating ITP that is approximately 10 times the dose for Rh immunoprophylaxis, and the expected serologic incompatibility with recipients' D+ RBCs.     

The production of red blood cell alloantibodies in mice transfused with blood from transgenic Fyb-expressing mice

BACKGROUND: A murine model would be useful to identify which immune mechanisms could be manipulated to treat or prevent red blood cell (RBC) alloimmunization in patients who become sensitized to multiple or widely expressed antigens. STUDY DESIGN AND METHODS: Transgenic mice (B6CBAF1/J-Tg-Fy(b)) expressing the human Fy(b) antigen of the Duffy (Fy) blood group were donors. Recipient B6CBA-F1 mice received four weekly intravenous (IV) transfusions: either 0.3 mL of washed buffy coat-depleted RBCs or 0.3 mL of RBCs with spleen cells. Titers of immunoglobulin M (IgM) and immunoglobulin G (IgG) were measured in recipient serum samples by flow cytometry with RBCs from donor mice as target cells. Recipient serum samples were also tested against human RBCs of various Fy phenotypes. Additionally, RBC survival studies were performed in alloimmunized mice utilizing biotin-labeled Fy(b) transgenic mouse RBCs. RESULTS: B6CBA-F1 mice receiving washed buffy coat-depleted RBCs first made IgM, followed by IgG alloantibodies to transgenic mouse Fy(b)-positive RBCs. Recipients of Fy(b)-positive RBCs mixed with spleen cells also produced IgM and IgG alloantibodies, but at a slower rate than recipients of washed buffy coat-depleted RBCs. Serum samples showed specificity for Fy3, Fy(b), and Fy6. Decreased survival of transfused RBCs was evident at 24 hours after transfusion. CONCLUSIONS: It is possible to elicit the formation of anti-Fy alloantibodies by IV transfusion in mice that lack Fy antigens. The transfusion of RBCs alone was adequate to stimulate alloantibody production in B6CBA-F1 recipient mice. The survival of transfused Fy(b)-positive RBCs is diminished in sensitized mice. This model will be useful in further studies of RBC alloimmunization.     

Red blood cell alloimmunization in sickle cell disease patients in Uganda

BACKGROUND: Blood transfusion is an integral part in the management of sickle cell disease (SCD) patients. Alloimmunization is a recognized complication of red blood cell (RBC) transfusions with consequences including delayed hemolytic transfusion reactions and difficulties in getting compatible blood for future transfusions. The objective of this study was to determine the frequency of RBC alloimmunization in SCD patients in Uganda where pretransfusion screening for alloantibodies is not practiced.
STUDY DESIGN AND METHODS: In a cross-sectional study, SCD patients at Mulago Hospital Sickle Cell Clinic, Kampala, Uganda, were investigated. The demographic characteristics and transfusion history were recorded. Blood samples were drawn from consenting, previously transfused patients and RBC alloimmunization was demonstrated using immunohematologic techniques.
RESULTS: There were 428 patients (median age, 12 years; female/male ratio, 1.0) and they had received a median of 3 units in a median of three transfusion episodes. Twenty-six patients (6.1%) possessed RBC alloantibodies and 21 (80.7%) of them had received up to 10 transfusions. A total of 30 alloantibodies was found; 20 (66.7%) and 5 (16.6%) belonged to Rh and MNS blood groups, respectively. Five of the alloimmunized patients had multiple antibodies.
CONCLUSIONS: The rate of RBC alloimmunization in Ugandan SCD patients was 6.1%. The homogeneity between donors and SCD patients plus the low transfusion load may explain this immunization frequency. Nevertheless, our study confirms the significance of RBC alloimmunization as a complication in Ugandan SCD patients. Therefore, there is need to improve immunohematologic testing in Uganda so that RBC alloimmunization and its consequences may be prevented.     

Clinical significance of serologic markers related to red blood cell autoantibodies production after red blood cell transfusion—severe autoimmune hemolytic anemia occurring after transfusion and alloimmunization: successful treatment with rituximab

BACKGROUND: The association of autoantibody formation with blood transfusion was previously noted. Severe autoimmune hemolytic anemia (AIHA) diagnosed after red blood cell (RBC) transfusion determined us to undertake this study and investigate the incidence and clinical significance of autoantibodies occurring after transfusion by a retrospective review of blood bank and medical records.
STUDY DESIGN AND METHODS: We report a lymphoma patient who developed severe autohemolysis after blood transfusion and alloantibody production. The hemolysis was refractory to steroids and chemotherapy and ceased after rituximab. We also retrospectively assessed the blood bank records for a 2-year period to identify the patients who developed autoantibodies after blood transfusion and examined laboratory, clinical features, and outcome.
RESULTS: From January 2005 through December 2006, 375 direct antiglobulin tests (DATs) and 3409 indirect antiglobulin tests (IATs) were found to be positive. Thirty-eight patients with positive DATs and IATs had demonstrable RBC warm-type autoantibodies occurring after blood transfusion; 27 of them had also one or more alloantibodies. Clinical and laboratory signs of hemolysis were absent in all patients (except the case reported). In another 5 patients alloantibodies were retrieved from RBC eluate and serum without evidence of autoantibodies; therefore, a delayed serologic transfusion reaction was diagnosed.
CONCLUSION: RBC autoantibodies are quite commonly found after blood transfusion. Nevertheless, clinically significant AIHA is a rare but at times a life-threatening phenomenon. We describe a first case of successful treatment with rituximab of refractory posttransfusion AIHA. Rituximab must be further evaluated for this indication.     

Anti-i causing acute hemolysis following a negative immediate-spin crossmatch

A unique case of acute hemolysis following transfusion of red cells (RBCs) that were found compatible by immediate-spin (IS) crossmatch technique is reported. Screening tests for unexpected antibodies, using low-ionic-strength saline (LISS), 10 minutes' incubation at 37 degrees C, and anti-IgG, were nonreactive; however, 1 transfused unit was found crossmatch incompatible by indirect antiglobulin technique (IAT). An anti-i (titer 512 at 4 degrees C) that was not an autoantibody was identified in the patient's serum. Unlike the incriminated donor RBCs, most I+ RBCs did not react by LISS-IAT. Variable reactivity was seen with ficin-treated I+ RBCs, and there was marked hemolysis of iadult and icord RBCs. In marked contrast, dominant Lu(a-b-) RBCs, with reduced expression of i, did not react by any test method; nor did autologous I+, Lu(b+) RBCs. The in vivo clinical significance of this anti-i was confirmed by monocyte monolayer assay and RBC survival studies. The patient's i antigen may have been altered, by either chemotherapy or disease, and lacked part of the i antigen-mosaic. Her antibody was directed at epitopes of i that were absent from her RBCs. Those i epitopes missing from her RBCs are also absent on dominant Lu(a-b-) RBCs. This anti-i represents a unique cause of an acute hemolytic transfusion reaction. It also represents a case of acute immune-mediated hemolysis following transfusion of IS crossmatch-compatible blood when screening tests for unexpected antibodies are nonreactive. Because of the rarity of such cases (less than 1/200,000 RBC units transfused), modifications to pretransfusion testing protocols are not proposed.