Comparison of ABO antibody titration, IgG subclasses and qualitative haemolysin test to reduce the risk of passive haemolysis associated with platelet transfusion

A study on diagnostic performance of different immunohematological diagnostic tests in assessing the prevalence of ABO Hemolytic Disease of Newborn in the antenatal O group mothers and their neonatal outcome in a tertiary care hospital in Northern India

BACKGROUND

Hemolytic disease of the newborn (HDN) results in the decreased lifespan of the red cells. HDN related to ABO incompatibility is mostly unnoticed because routine screening is not being done. This study was done to assess the prevalence of ABO-HDN and to compare different immunohematological tests. Methods-In this study 213 O group mothers and the 122 ABO-incompatible newborns born to them were included. Quantifying the maternal IgG anti-A/anti-B antibody titer was done by Conventional Tube Technique (CTT) using Dithiothreitol (DTT) pretreated maternal serum. Hemolysin test was performed on the mothers having titer > 256. These cases were followed up and, after delivery, were monitored for ABO HDN, along with direct antiglobulin testing and elution studies. The prevalence of ABO-HDN was calculated, and the different diagnostic parameters of the tests were calculated. Results- The prevalence of ABO-HDN in our population was estimated to be 1.7%, 6.1% & 10.6% in our population, O group mothers, and O group mothers with ABOincompatible newborns, respectively. Maternal titer≥ 512 strongly correlated with ABOHDN. DAT positivity is a good predictor of ABO-HDN, especially using sensitive techniques. Maternal IgG titers have the highest sensitivity & Negative Predictive Value, while DAT has the highest specificity & Positive Predictive Value. Conclusion - Maternal ABO antibody titration may be advocated in the centers to identify high-risk groups. It can advocate institutional delivery and dedicated follow-up of newborns with ABO-HDN. Blood grouping & DAT may be performed in all newborns born to O blood group to identify high-risk cases.

Characteristics of ABO Antibodies in Group O Malaysian Blood Donors

Background

Haemolytic transfusion reactions (HTRs) due to anti-A and anti-B antibodies in Group O blood products are rare but potentially fatal. This study aimed to identify the prevalence of high ABO antibody titre and the immunoglobulin (Ig) classes (IgM only or with IgG) and the prevalence of haemolysin antibodies in Group O blood donors.

Methods

Plasma from Group O blood donors was tested by using antibody titration at room temperature. Titres ≥ 64 were considered high. The plasma was treated with 0.01 M dithiothreitol (DTT) to determine the presence of IgG antibodies and titre. IgG titres ≥ 64 were considered high. Tests for haemolysis were conducted by mixing the plasma with 3% fresh A1 and B cell suspensions and incubating at 37 °C. The haemolysis was observed macroscopically.

Results

Of 311 donors, 238 (76.5%) showed high anti-A and/or anti-B antibody titres. The highest antibody titre obtained was 256. Female and younger donors (< 40 years old) had higher anti-A and anti-B titres. The anti-B titre showed an association with gender (P < 0.001), and was high in female donors (77.8%). Males aged over 50 years old were found to have low mean titre antibodies. Most donors had both IgM and IgG ABO antibodies. The prevalence of haemolysins in our population was 3.5%.

Conclusion

Most of our O blood donors had a high ABO antibody titre but a low prevalence of haemolysins. Males aged over 50 years old are the best O donors for preventing HTRs, particularly when mismatch transfusion is required. We recommend a transfusion unit screen for ABO antibody titre in younger female donors (< 40 years old), to prevent the transfusion of high titre O blood products into non-O recipients.

Lower Levels of ABO Anti-A and Anti-B of IgM, IgG and IgA Isotypes in the Serum but Not the Saliva of COVID-19 Convalescents

Individuals with ABO type O, naturally possessing anti-A and anti-B antibodies in their serum, are underrepresented among patients infected with SARS-CoV-2 compared with healthy controls. The ABO antibodies might play a role in the viral transmission. Therefore, we aimed to quantify anti-A/anti-B, including their subclasses IgM, IgG and IgA, in the serum and saliva of Caucasians (n = 187) after mild COVID-19 to compare them with individuals who had never been infected with SARS-CoV-2. Two samples were collected within two months after the diagnosis (median days: 44) and two months later. ABO antibodies were determined by flow cytometry. Additionally, total IgA in saliva and antibodies specific to SARS-CoV-2 were tested by ELISA. COVID-19 convalescents had significantly lower levels of anti-A/anti-B IgM, IgG and IgA in their serum than control subjects (p < 0.001). Interestingly, no significant differences were observed in saliva. ABO antibody levels remained stable over the period considered. No relation of ABO to the level of SARS-CoV-2-specific antibodies was observed. Total IgA was lower in convalescents than in controls (p = 0.038). Whereas ABO antibodies in the saliva may not contribute to the pathogenesis of COVID-19, individual pre-existing high serum concentrations of anti-A/anti-B may have a protective effect against SARS-CoV-2 infection.

High titers of anti-A1 and anti-B antibodies among Peruvian group O platelet donors

Critical antibody titers have been described as factors associated with hemolysis in ABO plasma-incompatible platelet (PLT) transfusions. This study was carried out to describe the frequency of high-titers anti-A and antiB IgM and IgG antibodies in group O apheresis platelet donors, and to explore differences according to the donor characteristics. A cross-sectional study was carried out at the Blood Bank of a National Hospital in Peru from January to March 2019. IgM and IgG antibodies against A1 and B antigens were quantified in 339 platelet donors using the direct hemagglutination technique and the solid-phase adherence technique, respectively. For analysis purposes, two cut-off points; ≥128 and ≥64, were used to define a critical titer for IgM due to a lack of consensus. An IgG titer of ≥256 was also defined as critical. Of the donors, 22.1 % had critical IgM titers when the cut-off point was defined as ≥128. However, when the IgM cut-off was ≥64, the frequency of platelet donors with critical titers increased to 54.0 %. The frequency of donors with critical IgG titers was 23.5 %. Higher IgG titers were associated with female donors while higher IgM titers were negative associated with age. One in two or three platelet donors, depending on the cutoff point used to define a critical IgM titer, had at least one critical titer of anti-A or anti-B antibodies. Early identification of platelet donors with critical antibody titers could prevent passive transfusion of ABO antibodies to non-isogroup recipients.

Risk of ABO-Incompatible Plasma From Non-ABO-Identical Components

The last several decades have seen significant changes in the approach to resuscitation of bleeding patients. These include the adoption of ABO-incompatible plasma transfusion in the form of group A plasma and/or low titer group O whole blood for trauma patients of unknown ABO group. Studies to date have examined the impact of these practices on patient outcomes and clinical markers of hemolysis in recipients of ABO-incompatible plasma compared to those for whom the plasma is ABO-compatible. Risk for increased mortality and/or overt hemolysis appear to be low among recipients of ABO-incompatible plasma; however, nearly all of studies are retrospective and most have focused only on adult trauma patients so results may not be generalizable to other bleeding patients. Work continues to evaluate the role of various titer thresholds in decreasing hemolytic risk and opportunities remain to improve our understanding of anti-A and anti-B antibody interactions with complement/endothelium and identify strategies to minimize risk.

ABO antibody titer performance characteristics and correlates between two automated platforms

BACKGROUND

AABB standards require a policy for assessing transfusing ABO-incompatible plasma. After a fatal hemolytic event with incompatible plasma, our institution instituted platelet donor population titer method for ABO antibodies on the PK7300, with high-titer being defined as having isohemagglutinin titers greater than 256. We recently switched titering platforms to the Neo Iris and we seek to determine the equivalent isohemagglutinin high-titer cutoff on the Neo Iris as compared to the PK7300.

METHODS

We measured the titers on 299 apheresis platelet donors and compared its performance characteristics at various cutoffs to the PK7300 reference standard. Discrepant results were manually diluted and retested on the Neo Galileo. Furthermore, since the Neo Iris is able to determine isotype and antigen specific titers, we also characterized these features in our donor population.

RESULTS

IgM titer of 128 on the Neo Iris has better accuracy compared to the titer of 64 (94 % vs 93.6 %). Eleven of sixteen discordant results were in agreement with Neo Iris. Blood group O had the highest IgG antibody titers for both anti-A and anti-B (p = 8.4E-17 and 4.3E-09, respectively). Additionally, group O donors exhibited lower anti-A2 than anti-A1 IgG titers.

DISCUSSION

The Neo Iris titer cut-off of 128 had the best overall accuracy and correlation with a 256 cut-off on our laboratory developed test on the PK7300 platform. Additionally, we found that group O donors had the highest titer antibodies, with typically higher IgG titers than IgM, and generally multiple dilution levels greater than other blood types.