Evaluating the clinical significance of blood group alloantibodies that are causing problems in pretransfusion testing

Monocyte monolayer assay in pre-transfusion testing: A magic key in transfusing patients with recurrent bad cross-match due to alloimmunization

BACKGROUND

The monocyte monolayer assay (MMA) is an in-vitro assay that can predict the outcome of blood transfusion of antigen positive units when serologically compatible blood is not available.

MATERIALS AND METHODS

Fifty-four patients testing positive by the antibody screening test using gel agglutination were further examined by the alloantibody identification panel to determine alloantibody specificity. After determining and categorizing the antibodies, patients' samples were examined using the MMA to determine the clinical significance of the detected alloantibodies. We also tested 2 seeding methods (24-well cell culture plates versus 8-well chamber-slides) and 3 visualization/staining techniques (unstained phase contrast, Leishman and Giemsa staining).

RESULTS

35 out of the 54 cases (64.8%) had a monocyte index of >5% which is predictive of occurrence of hemolytic reaction after transfusion; 23 cases with antibodies known to be clinically significant [anti-C, anti-E, anti-c, anti-K, anti-Fy(a), anti Fy(b), anti-JK(b)], 2 with Anti-M specificity, 7 cases with autoantibodies and 3 cases with multiple antibodies. On the other hand, 19 out of the 54 (35.2%) cases included in the study showed a monocyte index of <5% which is predictive of absence of hemolytic reaction after transfusion. The 8-well chamber-slides were better than the 24-well culture plates, as the latter showed a lot of un-phagocytosed RBCs in the background. Also, Leishman staining was better than Giemsa staining with better and clearer differentiation between the RBCs, monocytes and phagocytic vacuoles.

CONCLUSION

MMA can be used as a surrogate cross-match test for the selection of blood units in cases where antigen-negative blood units are not available.

Activity, specificity, and titer of naturally occurring canine anti–DEA 7 antibodies

The reported prevalence of naturally occurring anti–dog erythrocyte antigen (DEA) 7 antibodies in DEA 7–negative dogs is as high as 50%. Characterization of these antibodies may better define their importance in canine transfusion medicine. We determined in vitro activity, specificity, and titer of anti–DEA 7 antibodies in DEA 7–negative dogs. Plasma samples from 317 DEA 7–negative dogs were cross-matched with DEA 7–positive red blood cells (RBCs) using gel column technology. Agglutination occurred with DEA 7–positive RBCs but not with DEA 7–negative RBCs in 73 samples (23%), which were hence classified as containing anti–DEA 7 antibodies. These samples were evaluated for hemolytic and agglutinating activity, strength of agglutination, and antibody specificity and titers. All samples showed agglutination but none showed hemolysis. Gel agglutination was graded as 1+ for 20 samples (27%), 2+ for 49 samples (67%), 3+ for 4 samples (6%); no samples were graded 4+. The agglutination titer was <1:2 for 51 samples (73%), 1:2 for 13 samples (19%), 1:4 for 4 samples (5%), and 1:8 for 2 samples (3%). Of 16 samples treated with 2-mercaptoethanol, 11 samples (69%) contained only IgM, 4 samples (25%) exhibited only IgG activity, and 1 sample (6%) had both IgG and IgM activity. Low titers of warm, weakly agglutinating, mostly naturally occurring IgM anti–DEA 7 antibodies were found in 23% of DEA 7–negative dogs. The presence of naturally occurring anti–DEA 7 antibodies suggests that cross-matching of canine blood recipients is advisable, even at first transfusion, to minimize delayed transfusion reactions.

Successful transfusion of antigen positive blood to alloimmunised patients using a monocyte monolayer assay

BACKGROUND

Providing adequate transfusion support for alloimmunised patients for whom antigen negative blood is not readily available is hampered by the risk of a haemolytic reaction. The monocyte monolayer assay (MMA) has shown good correlation between the antibody clinical significance and the fate of antigen positive blood.

MATERIALS AND METHODS

From 2006 to 2013, the clinical significance of red cell alloantibodies produced by 61 patients was evaluated using a MMA; and antigen positive blood offering the best survival advantage was selected for transfusion following a secondary MMA crossmatch. Post-transfusion, patients were evaluated for clinical signs of haemolysis.

RESULTS

Overall, 19 of 61 (31·1%) of our antibodies were potentially clinically significant, with a monocyte index (MI) > 5%. There was no correlation between the clinical significance as showed by the MMA, and the specificity of the antibody or the strength of reactivity at antihuman globulin (AHG) phase. Using the MMA as a secondary crossmatch method, 31 alloimmunised patients (including: eight anti-hr(B), four anti-Yt(a), one each anti-Rg1, -Co(a), Er(a), Le(b), -LW, -Sl1) received 103 antigen positive blood units with no clinical sign of a post-transfusion reaction. For three patients (one each anti-Jo(a), -AnWj, unidentified 'HTLA'), initial MMA was performed as part of an investigation of a suspected haemolytic reaction. In each case, the MMA accurately identified the unit responsible for the reaction.

CONCLUSION

Used as a crossmatch surrogate, the MMA provided valuable information in the decision of transfusing antigen positive blood to alloimmunised patients, avoiding delay because of the search of rare antigen negative units.

Pathology consultation on electronic crossmatch

OBJECTIVES

The full crossmatch is traditionally the final step in compatibility testing, acting as a serologic double check for ABO compatibility and unexpected RBC antibodies. In this review, we discuss the development of electronic crossmatch (EXM), an approach for determining when EXM can be used, and its strengths and weaknesses.

METHODS

Because EXM relies on highly sensitive screening assays, antibodies are frequently encountered whose clinical significance must be investigated and interpreted. Our approach is to obtain further history, perform enhanced tube testing, and consider tests of immune reactivity or RBC survival.

RESULTS

For those without clinically significant antibodies, we found two alternatives: immediate-spin crossmatch (IS XM) and EXM. IS XM is prone to error related to serologic interference, whereas EXM depends on the accuracy of the sample label, accurate data entry, and informatics to avoid errors.

CONCLUSION

EXM is an alternative to the serologic test in patients who have no clinically significant antibodies.

The Rh allele frequencies in Gaza city in Palestine

Background:

The Rh blood group system is the second most clinically significant blood group system. It includes 49 antigens, but only five (D, C, E, c and e) are the most routinely identified due to their unique relation to hemolytic disease of the newborn (HDN) and transfusion reactions. Frequency of the Rh alleles showed variation, with regard to race and ethnic.

Objectives:

The purpose of the study was to document the Rh alleles’ frequencies amongst males (M) and females (F) in Gaza city in Palestine.

Materials and Methods:

Two hundred and thirty-two blood samples (110 M and 122 F) were tested against monoclonal IgM anti-C,anti-c, anti-E, anti-e and a blend of monoclonal/polyclonal IgM/IgG anti-D. The expected Rh phenotypes were calculated using gene counting method.

Results:

The most frequent Rh antigen in the total sample was e, while the least frequent was E.The order of the combined Rh allele frequencies in both M and F was CDe > cDe > cde > CdE > cDE > Cde > CDE. A significant difference was reported between M and F regarding the phenotypic frequencies (P < 0.05). However, no significance (P > 0.05) was reported with reference to the observed and expected Rh phenotypic frequencies in either M or F students.

Conclusion:

It was concluded that the Rh antigens, alleles and phenotypes in Gaza city have unique frequencies, which may be of importance to the Blood Transfusion Center in Gaza city and anthropology.

A retrospective analysis of the value of monocyte monolayer assay results for predicting the clinical significance of blood group alloantibodies

BACKGROUND

Cellular assays (e.g., monocyte monolayer assays [MMAs]) have been used to predict the clinical significance of red blood cell (RBC) alloantibodies.

STUDY DESIGN AND METHODS

Twenty years of MMA data were retrospectively analyzed to 1) determine the optimal cut point (by correlating MMA results from 46 patients with RBC survival study results and/or laboratory and clinical signs of hemolytic transfusion reactions [HTRs] when incompatible blood was transfused), and 2) determine what percentage of 251 unusual alloantibodies (most to high-incidence antigens) were predicted to be clinically significant.

RESULTS

Two MMA cut points (5% and 20%) were chosen using a receiver-operating characteristics curve. No patients with MMA results less than or equal to 5 percent had clinical signs of a reaction; one-third of patients with MMA results 5.1 to 20 percent versus two-thirds with results greater than 20 percent had clinical signs of a HTR after transfusion of incompatible blood. Using 5-percent or 20-percent cut points, 173 (69%) or 97 (39%) of 251 unusual alloantibodies gave positive MMAs, respectively.

CONCLUSION

A negative MMA (< or =5%) indicates that incompatible blood can be given without risk of an overt HTR but does not guarantee normal long-term survival of those RBCs. Most unusual alloantibodies are predicted to cause shortened RBC survival, but transfusion of incompatible blood may not result in any clinical or laboratory signs of a HTR. We have used the MMA for approximately 20 years, instead of a 1-hour chromium-51 RBC survival, to aid in the decision to transfuse RBCs incompatible with antibodies to high-incidence antigens.

Red blood cell support and alloimmunization rate against erythrocyte antigens in patients undergoing hematopoietic stem cell transplantation

We retrospectively analyzed red blood cell (RBC) support and alloimmunization rate in 218 consecutive patients - 128 from the Pediatric Department and 90 from the adult Hematology Department - undergoing hematopoietic stem cell transplantation (HSCT) between 1994 and 2000. In the pre-HSCT period, the pediatric patients undergoing auto-HSCT required more RBC support. In the post-HSCT period, pediatric patients transplanted with an unrelated donor required more RBC support (median 13.5 U/10 kg bw) than patients receiving HSCT from a related donor (median 6 U/10 kg bw) or from an autologous source (median 4 U/10 kg bw, P=0.0004). In the pre-HSCT period, 159 out of 218 patients (73%) received a total of 1843 RBC units, with an overall median of 9 U/patient over a median of 24 months (range 4-62); 10 patients (6%) developed a total of 12 alloantibodies, with an alloimmunization rate of 5.4/1000 RBC units. In the post-HSCT period, all but three patients were given a total of 2420 RBC units, with an overall median of 6 U/patient over a median of 4 months (range 1-18); all but one of the pre-existing alloantibodies disappeared and three patients (1%) developed new alloantibodies with an alloimmunization rate of 1.2/1000 RBC units. These newly produced alloantibodies (one anti-M and two anti-E) were detected at +58, +90 and +210 days after HSCT. These findings might suggest a different approach to alloantibody screening tests in patients receiving HSCT, with a subsequent reduction of costs and laboratory workload.

Transfusion of incompatible RBCs to a patient with alloanti-Kp(b)

BACKGROUND

The finding of an antibody that reacts against a high-incidence blood group antigen always constitutes a complex transfusion problem because of the difficulty in finding compatible units. When the transfusion of incompatible RBCs is imperative, it would be of great interest to have access to techniques facilitating the prediction of the transfusion outcome.

STUDY DESIGN AND METHODS

The case of a patient with alloanti-Kp(b) who required RBC transfusions is reported. The functional activity of this antibody was assessed by both the chemiluminescence test (CLT) and the survival of 51Cr-labeled RBCS:

RESULTS

The CLT showed an opsonic index of 0.8 with Kp(b)-positive RBCs (normal values up to 1.6) in pretransfusion studies. During an elective surgical procedure, the patient required the transfusion of one incompatible unit of RBCs, which did not produce hemolysis. Two weeks after this incompatible transfusion, the opsonic index had risen to 11. Results of the 51Cr in vivo study, also performed at that time, indicated 24.3 percent survival of Kp(b)-positive RBCs at 60 minutes and 2.0 percent at 24 hours.

CONCLUSION

Results of the CLT correlated with the in vivo transfusion outcome and later with the 51Cr survival study.