Feasibility of the automated column agglutination technique for titration of anti-A/B antibodies in ABO-incompatible living kidney transplantation

INTRODUCTION

Quantitative measurement of anti-A/-B antibody titers is important during ABO-incompatible living kidney transplantation (ABOi-LKT).

METHODS

We conducted a multi-institutional study to measure the antibody titers using the automated column agglutination technique (auto-CAT) and tube test (TT) method in ABOi-LKT recipients. Statistical analysis was performed to evaluate the two methods.

RESULTS

We examined 111 samples from 35 ABOi-LKT recipients at four institutions. The correlation coefficient of the two methods was >0.9; the concordance rate and clinically acceptable concordance rate for the IgG titers were 60.4% and 88.3%, respectively. Perioperative status did not influence the statistical significance. Parallel changes were observed in the IgG antibody titers measured using the auto-CAT or TT technique by desensitizing therapy in time-course monitoring.

CONCLUSION

Auto-CAT is comparable with the TT technique and is feasible for IgG anti-A/B antibody titration in ABOi-LKT recipients.

Comparative evaluation of the conventional tube test and column agglutination technology for ABO antibody titration in healthy individuals: a report from India

Determination of accurate anti-A/-B titers is important for treatment selection in ABO-incompatible stem cell and solid-organ transplants. The standard method for ABO antibody titration is the conventional tube test (CTT). Dithiothreitol (DTT) is commonly used to inactivate the IgM antibody component. The aim of this study was to compare six different methods for ABO antibody titration and to observe the effectiveness of DTT on antibody estimation. A total of 90 healthy voluntary blood donors were enrolled in this study, including 30 each for blood groups A, B, and O. Antibody titrations were performed and tested using the CTT-immediate spin (IS), CTT-antihuman globulin (AHG) with and without DTT, column agglutination technology (CAT)-IS, and CAT-AHG with and without DTT methods. Bead-CAT was used, and the positive cutoff value was set to 1+ for each method to determine the endpoint of the titer. The median values of anti-A/-B titers by IS were found to be higher than those values by AHG in CTT and CAT among group B and A individuals, whereas no statistically significant differences were observed in values from group O individuals for IS and AHG anti-A/-B titers, estimated by each method. Although there was positive correlation between the anti-A/-B titer results obtained using the CTT and CAT in all blood groups, testing using AHG showed poor agreement with and without DTT pretreatment (kappa value of 0.11 and 0.20, respectively). Moderate agreement was observed between CTT-IS and CAT-IS (kappa value of 0.46). Median anti-A/-B AHG titers were reduced by the use of DTT in all blood group samples. Significant differences in the interpretability of anti-A/-B titers were observed among different methods. A uniform approach for selecting the method for ABO antibody titration is highly recommended, and DTT pretreatment of plasma to neutralize IgM activity should be considered to obtain precise values of IgG anti-A/-B titers. Immunohematology 2021;37:25-32 .

Determination of accurate anti-A/-B titers is important for treatment selection in ABO-incompatible stem cell and solid-organ transplants. The standard method for ABO antibody titration is the conventional tube test (CTT). Dithiothreitol (DTT) is commonly used to inactivate the IgM antibody component. The aim of this study was to compare six different methods for ABO antibody titration and to observe the effectiveness of DTT on antibody estimation. A total of 90 healthy voluntary blood donors were enrolled in this study, including 30 each for blood groups A, B, and O. Antibody titrations were performed and tested using the CTT-immediate spin (IS), CTT-antihuman globulin (AHG) with and without DTT, column agglutination technology (CAT)-IS, and CAT-AHG with and without DTT methods. Bead-CAT was used, and the positive cutoff value was set to 1+ for each method to determine the endpoint of the titer. The median values of anti-A/-B titers by IS were found to be higher than those values by AHG in CTT and CAT among group B and A individuals, whereas no statistically significant differences were observed in values from group O individuals for IS and AHG anti-A/-B titers, estimated by each method. Although there was positive correlation between the anti-A/-B titer results obtained using the CTT and CAT in all blood groups, testing using AHG showed poor agreement with and without DTT pretreatment (kappa value of 0.11 and 0.20, respectively). Moderate agreement was observed between CTT-IS and CAT-IS (kappa value of 0.46). Median anti-A/-B AHG titers were reduced by the use of DTT in all blood group samples. Significant differences in the interpretability of anti-A/-B titers were observed among different methods. A uniform approach for selecting the method for ABO antibody titration is highly recommended, and DTT pretreatment of plasma to neutralize IgM activity should be considered to obtain precise values of IgG anti-A/-B titers. Immunohematology 2021;37:25–32 .

Group O blood donors in Iran: evaluation of isoagglutinin titers and immunoglobulin G subclasses

This study aims to determine the most frequent titers of anti-A and anti-B (both presumed immunoglobulin [Ig]M and IgG) in Iranian group O blood donors and to compare these titer values with those found in other studies. In addition, alloantibody production and plasma levels of four IgG subclasses were compared between the high-titer and non-high-titer study groups. This study investigated anti-A and anti-B titers in 358 plasma samples. Based on these results, two study groups (high-titer and non-high-titer) were formed. Antibody detection tests were performed to detect unexpected antibodies to D, C, c, E, e, K, k, Fy^a, Fy^b, Jk^a, Jk^b, M, N, S, s, P1, Le^a, and Le^b. Four IgG subclasses were also evaluated through nephelometry assay. The most frequent titer obtained by room temperature and indirect antiglobulin tube tests was 256. The frequency of titers ≥512 was 31.5 percent. None of the cases showed unexpected RBC alloantibodies. IgG2 levels were significantly higher in the high-titer group. Evaluation of isoagglutinin titers in group O Iranian blood donors can provide insight into the frequency of isoagglutinin titers both within the Iranian population and as compared with other populations. A significant difference in IgG2 levels between the high-titer and non-high-titer groups was identified. More investigation needs to be conducted on the root cause of this finding. Immunohematology 2021;37:5-12 . This study aims to determine the most frequent titers of anti-A and anti-B (both presumed immunoglobulin [Ig]M and IgG) in Iranian group O blood donors and to compare these titer values with those found in other studies. In addition, alloantibody production and plasma levels of four IgG subclasses were compared between the high-titer and non–high-titer study groups. This study investigated anti-A and anti-B titers in 358 plasma samples. Based on these results, two study groups (high-titer and non–high-titer) were formed. Antibody detection tests were performed to detect unexpected antibodies to D, C, c, E, e, K, k, Fy^a, Fy^b, Jk^a, Jk^b, M, N, S, s, P1, Le^a, and Le^b. Four IgG subclasses were also evaluated through nephelometry assay. The most frequent titer obtained by room temperature and indirect antiglobulin tube tests was 256. The frequency of titers ≥512 was 31.5 percent. None of the cases showed unexpected RBC alloantibodies. IgG2 levels were significantly higher in the high-titer group. Evaluation of isoagglutinin titers in group O Iranian blood donors can provide insight into the frequency of isoagglutinin titers both within the Iranian population and as compared with other populations. A significant difference in IgG2 levels between the high-titer and non–high-titer groups was identified. More investigation needs to be conducted on the root cause of this finding. Immunohematology 2021;37:5–12 .

Comparative evaluation of DTT treated ABO isoagglutinin titres performed by two methods with solid phase red cell adhesion (SPRCA) titres

BACKGROUND AND AIMS

Measurement of actual concentration of IgG requires methods like treatment of serum with dithiothreitol (DTT). This study was aimed at comparing of DTT treated ABO titres performed by conventional test tube technique (CTT) and column agglutination technique (CAT) with HA/SPRCA.

MATERIALS AND METHODS

This was a prospective, observational study conducted from October 2019 to March 2020. All consecutive A, B and O group donors who gave consent for participation were included. All samples were tested by CTT and CAT before and after DTT treatment (pCTT, pCAT) and with HA/SPRCA.

RESULTS

A total of 300 donors were included; 100 each from A, B and O blood group donors. Group O titres were higher than group A/B titres. Group O titres were highest when performed by pCAT, followed by pCTT and lowest by HA/SPRCA. Group A/B titres were highest when performed by HA/SPRCA, followed by pCAT and pCTT for anti-A and highest when performed by pCAT, followed by HA/SPRCA and lowest by pCTT for anti-B.

CONCLUSION

Results obtained by pCAT were closer to results obtained by pCTT, whereas those obtained by HA/SPRCA were variable. SPRCA offers the advantage of automation, no inter-observer variation and less time consumption because IgM interference is not observed with SPRCA, thus providing an alternative to pCTT. However, these methods cannot be used interchangeably and to discern the most suitable method, a clinical impact of these results needs to be studied.

Outcome of desensitization in human leukocyte antigen and ABO incompatible living donor kidney transplantation: Single center experience of first 200 incompatible transplants

BACKGROUND AND AIMS

Although desensitization is well established, concerns about graft outcome, patient survival and rejection still exist. The present study aims at comparing outcomes of renal transplant recipients across simultaneous ABO and human leukocyte antigen (HLA) incompatibility barriers to those with ABO or HLA incompatibility alone.

MATERIALS AND METHODS

This was a retrospective study conducted from October 2015 to December 2018. All patients with a clinical diagnosis of chronic kidney disease, who were prospective HLA incompatible (HLAi) and/or ABO incompatible (ABOi) renal transplant recipients were included. A total of 400 cases including 36 ABOi transplants, 154 HLAi transplants, 10 simultaneously ABO and HLA incompatible transplants, and 200 ABO (ABOc) and HLA (HLAc) compatible kidney transplants from living donors were included.

RESULTS

There were significantly more number of blood transfusions, previous transplants and pregnancies in HLAi transplant recipients relative to the ABOi or the control group. Mean number of therapeutic plasma exchange procedures per patient and mean plasma volume processed per procedure were slightly higher in the ABOi + HLAi category. The incidence of graft dysfunction due to suspected antibody-mediated rejection during first year was highest in the ABOi + HLAi group, followed by ABOc + HLAi and ABOi + HLAc, lowest in the ABOc + HLAc category. Mean time to first episode of graft dysfunction was significantly shorter with incompatible transplants. There were no kidney transplant recipient deaths in the study.

CONCLUSION

Patient outcome and graft outcomes observed with incompatible transplants were not worse than those observed with compatible transplants.

An exploration of the advantages of automated titration testing: low inter-instrument variability and equivalent accuracy for ABO and non-ABO antibody titres relative to tube testing

BACKGROUND AND OBJECTIVES

Obtaining IgM and IgG titres is important in numerous clinical situations, including solid-organ transplant, obstetrics, and for testing of out-of-group plasma-containing components. Tube method is the most prevalent testing modality, though it is both labour-intensive and known for intra- and inter-laboratory variability. The utility of automated gel testing as a method to improve both inter- and intra-laboratory reproducibility is unknown.

MATERIALS AND METHODS

Two academic centres participated in a study evaluating automated gel titreing. Group O plasma samples were used to measure titres of antibodies against ABO (IgM) with buffered gel cards and 4 minor and minor red-blood-cell antigens (IgG) anti-IgG gel cards. Multiple ORTHO VISION automated analyzers were used to assess inter-instrument variation. A subset of ABO (IgM) samples were compared between laboratories to evaluate inter-laboratory variability. Multiple samples were titred by tube and by automated gel technology to determine similarity of results.

RESULTS

Testing demonstrated no significant difference between analysers or between sites when performing automated titrations (P ≥ 0·99). Non-ABO IgG titres were evaluated and demonstrated little inter-instrument variability. The IgM anti-A and -B titres obtained by automated gel testing were neither consistently higher nor lower than tube titres. Greater than 90% of titre values were within one dilution.

CONCLUSION

Based on this study, our data suggest that titreing by automated gel testing is both highly reproducible (IgM and IgG) and does not differ significantly from manual tube testing results of direct agglutination (IgM).

Standardization of ABO antibody titer measurement at laboratories in Korea

Background

Measurement of the ABO antibody (Ab) titer is important in ABO-incompatible transplantation. However, to the best of our knowledge, no standard protocol or external survey program to measure the ABO Ab titer has been established in Korea. We investigated the current status of ABO Ab titer measurements at various laboratories in Korea and the impact of the protocol provided to reduce interlaboratory variations in the methods and results of ABO Ab titers.

Methods

The Korean external quality assessment of blood bank laboratories sent external survey samples with a questionnaire to 68 laboratories across Korea for the measurement of ABO Ab titers in May 2012. After 6 months, a second set of survey samples were sent with a standard protocol to 53 of the previously surveyed laboratories. The protocol recommended incubation at room temperature only and use of the indirect antihuman globulin method for the tube test as well as and the column agglutination test (CAT).

Results

Several interlaboratory variations were observed in the results, technical procedures, and methods selected for measurement. We found that 80.4% laboratories hoped to change their protocol to the provisional one. Additionally, CAT showed significantly lower variation among laboratories (P=0.006) than the tube test.

Conclusions

Our study provides baseline data regarding the current status of ABO Ab titer measurement in Korea. The standard protocol and external survey were helpful to standardize the technical procedures and select methods for ABO Ab titer measurement.

Comparison of ABO antibody titers on the basis of the antibody detection method used

BACKGROUND

Detection methods for ABO antibody (Ab) titers vary across laboratories, and the results are different depending on the method used. We aimed to compare titer values using different detection methods for the measurement of ABO Ab titers.

METHODS

For ABO Ab detection, pooled group A or B red blood cells (RBCs) were reacted with each of 20 sera from blood groups A, B, or O without dithiothreitol treatment. The room-temperature (RT) incubation technique and the indirect antiglobulin test (IAT) were used in the tube test and gel card test. Flow cytometry (FCM) was performed by using anti-IgM and anti-IgG Abs.

RESULTS

Regardless of the blood groups tested, the FCM assay with anti-IgM showed the highest titer compared to the tube test and gel card test with RT incubation in both. The tube test with IAT showed a higher titer than the gel card test with IAT (Gel-IAT) or FCM with anti-IgG in blood group A and B, while Gel-IAT showed the highest titer relative to the other tests, only for the anti-A Ab in blood group O.

CONCLUSIONS

There were significant differences in the titers depending on the detection method used, and each method showed a different detection capacity for each ABO Ab depending on the ABO blood group tested. Therefore, caution should be exercised in interpreting ABO Ab titer results, taking into consideration the detection method used and the blood group.

ABO-incompatible kidney transplantation

PURPOSE OF REVIEW

A dramatic shortage of available organs around the world encouraged attempts to cross previously forbidden immunological boundaries in kidney transplantation. This review focuses on the recent results of ABO-incompatible kidney transplantation.

RECENT FINDINGS

The outcome of ABO-incompatible kidney transplantation in terms of patient and graft survival is comparable to ABO-compatible transplantation for adult and pediatric recipients. Splenectomy has been replaced by the B-cell-depleting agent rituximab to avoid isoagglutinin titer rebound, prevent antibody-mediated rejection, and improve graft survival. However, the risk for infections may be increased and warrants caution. Corticosteroids remain a necessary component of any ABO-incompatible protocol; early as well as late steroid withdrawal may bear an enhanced risk for acute rejection and should only be performed with careful follow-up including protocol biopsies. The few studies that have long-term outcomes using protocol biopsies have characterized a state of accommodation by up-regulation of complement inhibitors, down-regulation of A/B antigens, and establishment of endothelial chimerism over time.

SUMMARY

The experience accumulated around the world indicates that ABO-incompatible kidney transplantation is well tolerated and effective in adults and in children, and it represents an important step forward in expanding the living donor pool. Further understanding of ABO-incompatible graft accommodation may have broader implication also for human leukocyte antigen-sensitized allograft recipients.