High additional maternal red cell alloimmunization after Rhesus- and K-matched intrauterine intravascular transfusions for hemolytic disease of the fetus

The selection and preparation of red cell components for intrauterine transfusion: A national survey

BACKGROUND AND OBJECTIVES

The practice regarding the selection and preparation of red blood cells (RBCs) for intrauterine transfusion (IUT) is variable reflecting historical practice and expert opinion rather than evidence-based recommendations. The aim of this survey was to assess Canadian hospital blood bank practice with respect to red cell IUT.

MATERIALS AND METHODS

A survey was sent to nine hospital laboratories known to perform red cell IUT. Questions regarding component selection, processing, foetal pre-transfusion testing, transfusion administration, documentation and traceability were assessed.

RESULTS

The median annual number of IUTs performed in Canada was 109 (interquartile range, 103-118). RBC selection criteria included allogeneic, Cytomegalovirus seronegative, irradiated, fresh units with most sites preferentially providing HbS negative, group O, RhD negative, Kell negative and units lacking the corresponding maternal antibody without extended matching to the maternal phenotype. Red cell processing varied with respect to target haematocrit, use of saline reconstitution (n = 4), use of an automated procedure for red cell concentration (n = 1) and incorporation of a wash step (n = 2). Foetal pre-transfusion testing uniformly included haemoglobin measurement, but additional serologic testing varied. A variety of strategies were used to link the IUT event to the neonate post-delivery, including the creation of a unique foetal blood bank identifier at three sites.

CONCLUSION

This survey reviews current practice and highlights the need for standardized national guidelines regarding the selection and preparation of RBCs for IUT. This study has prompted a re-examination of priorities for RBC selection for IUT and highlighted strategies for transfusion traceability in this unique setting.

How do we perform intrauterine transfusions?

BACKGROUND

Intrauterine transfusion (IUT) is an invasive but critical and potentially life-saving intervention for severe fetal anemia with demonstrated improvement in outcomes. The fetus is vulnerable to hemodynamic alterations and transfusion-related adverse events; therefore, special consideration must be given to blood component selection and modification. There is widespread IUT practice variability, and existing guidance primarily relies on expert opinion and single center experiences.

STUDY DESIGN AND METHODS

Experts in Maternal Fetal Medicine, Pediatric Hematology, and Transfusion Medicine from centers across the United States, collectively performing about 120 IUT annually, offer a multidisciplinary perspective on the performance of IUT and preparation of blood components. This perspective includes strategies for identifying an at-risk fetus, communicating between disciplines, determining the necessary blood volume, selecting and processing blood components, documenting the procedure in medical record, and managing the neonate.

RESULTS

Identifying an at-risk fetus relies on review of the clinical history, non-invasive monitoring, and laboratory evaluation. We recommend the use of relatively fresh, group O, cytomegalovirus-safe, freshly irradiated, red blood cells (RBC) that are Hemoglobin S negative and antigen-negative for any maternal antibody, if indicated. These RBC units should be concentrated to remove additives and increase the hematocrit thus minimizing fluctuations in fetal volume status. The units intended for IUT should be labeled clearly and the documentation of transfusion differentiated in the maternal medical record.

DISCUSSION

An awareness of the technical, logistical, and regulatory considerations for IUT performance will facilitate improved communication and patient care, especially when rare units of RBC are required.

Double/Triple Intrauterine Blood Transfusion in Rh-isoimmunized Anemic Fetuses in Multiple Pregnancies with Favorable Outcome

Background

Multiple pregnancies have increased with the use of assisted reproduction, and we expect more women reporting with Rh isoimmunization among multiple gestation in near future. Intrauterine transfusion in singleton itself is technically difficult and requires a lot of skill and precision. Performing double/triple transfusion in twins/triplets is expected to be more demanding.

Aim

To create awareness on the technical difficulties encountered in intrauterine transfusion in twins and triplets.

Methodology

We report a case series of four Rh-isoimmunized twins/triplets in 5 years who presented with severe anemia requiring intrauterine transfusion.

Results

Each of the four sets of cases had their own intricacies that needed to be pondered before tackling them as not much was available in the literature. In Case 1, the first twin intrauterine transfusion in our 20-year-long experience, the difficulty in the approach to the first twin due to a posteriorly placed placenta has been highlighted. Case 2 was rare due to the concomitant presence of atypical antibodies in the mother in addition to Rh-D isoimmunization that made it difficult to cross match any donor blood for intrauterine transfusion. The third case was exclusive due to its monochorionic-diamniotic nature of the twins where the impact of inter-twin anastomosis on the transfusion was to be taken into consideration. Fourth case was a triplet gestation where the difficulty of which cord to be assigned to which fetus, the crowded space for intervention, as well as the risk of prolonged operative time and associated risk of preterm/premature rupture of membranes were our concern.

Conclusion

Intrauterine transfusion (IUT) in twins/triplets is challenging. Difficulties encountered during IUT in multifetal gestation are due to different or uncertain chorionicity, intraplacental anastomosis between vessels, different degree of anemia in twins, difficult to ascertain cord-fetus relationship and difficulty to reach placental insertion site due to crowding by multiple fetal parts.

Identification and management of fetal anemia due to hemolytic disease

INTRODUCTION

Hemolytic disease of the fetus and newborn (HDFN) is a condition caused by maternal alloantibodies against fetal red blood cells (RBCs) that can cause severe morbidity and mortality in the fetus and newborn. Adequate screening programs allow for timely prevention and intervention resulting in significant reduction of the disease over the last decades. Nevertheless, HDFN still occurs and with current treatment having reached an optimum, focus shifts toward noninvasive therapy options.

AREAS COVERED

This review focusses on the timely identification of high risk cases and antenatal management. Furthermore, we elaborate on future perspectives including improvement of screening, identification of high risk cases and promising treatment options.

EXPERT OPINION

In high-income countries mortality and morbidity rates due to HDFN have drastically been reduced over the last decades, yet worldwide anti-D mediated HDFN still accounts for 160,000 perinatal deaths and 100,000 patients with disabilities every year. Much of these deaths and disabilities could have been avoided with proper identification and prophylaxis. By implementing sustainable prevention, screening, and disease treatment measures in all countries this will systemically reduce unnecessary perinatal deaths. There is a common responsibility to engage in this cause.

Laboratory Monitoring of Mother, Fetus, and Newborn in Hemolytic Disease of Fetus and Newborn

Background

Laboratory monitoring of mother, fetus, and newborn in hemolytic disease of fetus and newborn (HDFN) aims to guide clinicians and the immunized women to focus on the most serious problems of alloimmunization and thus minimize the consequences of HDFN in general and of anti-D in particular. Here, we present the current approach of laboratory screening and testing for prevention and monitoring of HDFN at the Copenhagen University Hospital in Denmark.

Summary

All pregnant women are typed and screened in the 1st trimester. This serves to identify the RhD-negative pregnant women who at gestational age (GA) of 25 weeks are offered a second screen test and a non-invasive fetal RhD prediction. At GA 29 weeks, and again after delivery, non-immunized RhD-negative women carrying an RhD-positive fetus are offered Rh immunoglobulin. If the 1st trimester screen reveals an alloantibody, antenatal investigation is initiated. This also includes RhD-positive women with alloantibodies. Specificity and titer are determined, the fetal phenotype is predicted by non-invasive genotyping based on cell-free DNA (RhD, K, Rhc, RhC, RhE, ABO), and serial monitoring of titer commences. Based on titers and specificity, monitoring with serial peak systolic velocity measurements in the fetal middle cerebral artery to detect anemia will take place. Intrauterine transfusion is given when fetal anemia is suspected. Monitoring of the newborn by titer and survival of fetal red blood cells by flow cytometry will help predict the length of the recovery of the newborn.

Immunohematologic aspects of alloimmunization and alloantibody detection: A focus on pregnancy and hemolytic disease of the fetus and newborn

Alloimmunization to non-ABO, red blood cell (RBC) antigens remains one of the most clinically-relevant complexities faced by blood banking practitioners. In the setting of transfusion therapy, these antibodies raise risks for incompatibilities, while for pregnant patients they can mediate deadly forms of hemolytic disease of the fetus and newborn. As such, a thorough understanding of pathways that lead to alloimmunization, as well as the tools used by blood banks to detect alloantibodies, is critical to transfusion practice. In this review, in which alloimmunization in the setting of pregnancy will be emphasized, we will review: 1) the clinical impacts of RBC alloantibodies in the peri-partum period; 2) the current pathophysiologic mechanisms thought to influence non-ABO antigen alloimmunization; 3) the strengths and weaknesses of laboratory tools used in aiding alloimmunization detection; and 4) future directions of the transfusion community related to alloimmunization impacting pregnancy.

The prenatal intervention of pregnancy complicated with anti-Kell isoimmunization: a review

Since the first case of the hemolytic disease of the fetus and newborn (HDFN) caused by anti-K was reported in 1946, the fetal diagnosis of K-HDFN has made rapid progress from invasive immunological and biochemical tests to noninvasive Doppler ultrasound and molecular biology techniques. However, its treatment, especially prenatal intervention, has developed slowly compared with RhD-HDFN. This review attempts to clarify the current key points and explore the direction of the next phase by systematically reviewing the development of diagnosis and treatment of this disease, which involving multidisciplinary participation.

Fetal anemia

The diagnosis and management of fetal anemia has been at the forefront of advances in the fields of fetal physiology, immunology, fetal imaging, and fetal therapy among others. Alloimmunization and parvovirus infection are the leading cause of fetal anemia in the United States. The middle cerebral artery peak systolic velocity (MCA-PSV) diagnoses fetal anemia. Its discovery is considered one of the most important achievements in fetal medicine. Accumulation of experience in recent years as well as refinement of surgical techniques have led to safer invasive procedures. It is expected that long term follow-up of affected pregnancies, continues to reflect all these improvements in care. It is also expected that treatment of other less common causes of fetal anemia becomes more frequently reported and that the management principles of fetal anemia are successfully applied to other fetal pathologies.

Exposure to non-inherited maternal antigens by breastfeeding affects antibody responsiveness

The observation, by Ray Owen and colleagues in 1954, that D-negative women were less likely to form anti-D antibodies against their D-positive fetus if their mother possessed the D-antigen, was not found in all later studies. We hypothesized that breastfeeding, received by the mother, may affect her immunity against non-inherited maternal red blood cell antigens. We studied a cohort of 125 grandmother-mother-child combinations, from a follow-up study of mothers after intrauterine transfusion of the fetus for alloimmune hemolytic disease. For mismatched red blood cell antigens the mother was exposed to, whether or not antibodies were formed, we determined whether her mother, the grandmother, carried these antigens. The duration for which the mothers were breastfed was estimated by way of a questionnaire. Using multivariate logistic regression analyses, the interaction term (non-inherited maternal antigen exposure by categorized breastfeeding period) showed that a longer breastfeeding period was associated with decreased alloimmunization against non-inherited maternal antigens (adjusted odds ratio 0.66; 95% confidence interval 0.48–0.93). Sensitivity analysis with dichotomized (shorter versus longer) breastfeeding periods showed that this lower risk was reached after two months (aOR 0.22; 95% CI 0.07–0.71) and longer duration of breastfeeding did not seem to provide additional protection. These data suggest that oral neonatal exposure to non-inherited maternal red blood cell antigens through breastfeeding for at least two months diminishes the risk of alloimmunization against these antigens when encountered later in life.

Red Blood Cell Alloimmunization in the Pregnant Patient

Alloimmunization to red blood cell (RBC) antigens represents a challenge for physicians caring for women of child bearing potential. Exposure to non-self RBC antigens may occur during transfusion or pregnancy leading to the development of antibodies. If a subsequent fetus bears that antigen, maternal antibodies may attack the fetal red blood cells causing red cell destruction and clinically significant hemolytic disease of the fetus and newborn (HDFN). In the most severe cases, HDFN may result in intrauterine fetal demise due to high output cardiac failure, effusions and ascites, known as "hydrops fetalis". This article reviews strategies for management and prevention of RBC alloimmunization in women of child bearing potential.

Platelet Transfusion Induces Alloimmunization to D and Non-D Rhesus Antigens

Background

Platelet concentrates (PC) contain residual contaminating red blood cells (RBC), being higher in pooled buffy coat PC (BC-PC) than in apheresis units (AP-PC). Data about PC-induced alloimmunization against non-D Rhesus (Rh) antigens are limited.

Methods

For all newly detected RhD and non-D alloantibodies between August 2015 and September /2017 we prospectively evaluated if they were triggered through PC by analyzing for incompatible RBC and/or PC transfusions.

Results

We found 5,799 positive results in 89,190 antibody screening tests. We identified 13 newly detectable Rh antibodies through incompatible PCs in 11 patients: 6× anti-D, 4× anti-E, 2× anti-c, 1× anti-f. They received a total of 156 PC (83 BC-PC; 73 AP-PC): 5 patients received incompatible BC-PC only, 1 patient received incompatible AP-PC only, 5 patients received incompatible BC-PC and AP-PC. Quality control showed a mean (range) of 0.304 (0.152-1.662) and 0.014 (0.003-0.080) × 10⁹ RBC/l for BC-PC and AP-PC, respectively. Ten of the 11 patients received RBC transfusions, all of them being antigen-negative for the alloantibodies identified.

Conclusions

PC transfusions may not only induce RhD alloimmunization, but also immunization against further Rh antigens such as c, E, and f. The risk seems higher for BC-PC than for AP-PC. The results may have impact on future recommendations of PC transfusion with respect to Rh compatibility and upper limits of RBC contamination.

The HLA-DRB1*15 phenotype is associated with multiple red blood cell and HLA antibody responsiveness

BACKGROUND

Once a patient has produced a red blood cell (RBC) antibody, there is an increased risk of additional antibody formation after subsequent RBC exposure. Recently, we observed that HLA-DRB1*15 was overrepresented in 379 multiple RBC antibody responders compared to controls or 562 patients with a single RBC antibody (odds ratio [OR], 1.7; 95% confidence interval [CI], 1.3-2.3). In this study we evaluated whether the HLA-DRB1*15 represents a responder phenotype against HLA and/or RBC antigens.

STUDY DESIGN AND METHODS

HLA-DRB1*15 frequencies in single and multiple antibody responders were compared between three groups of individuals: 1) those with HLA antibodies, 2) those with RBC antibodies, and 3) those with both RBC and HLA antibodies.

RESULTS

A total of 3959 immunized patients (female-to-male ratio, 2.3) had been HLA-DRB1 typed. Among the 3275 individuals with HLA antibodies, the frequency of the DRB1*15 phenotype differed significantly from 19.7% in patients with a panel reactivity (PRA) of not more than 20% to 26.9% in patients with PRA of more than 80% (OR, 1.5; 95% CI, 1.2-1.9). This association between DRB1*15 and multiresponsiveness was mainly due to pregnancy-induced HLA immunization. In the 257 individuals with RBC and HLA antibodies, the frequency of DRB1*15 was 4.2 times (95% CI, 1.1-16) higher in those with multiple RBC antibodies and HLA-PRA of more than 50% compared to only single RBC responders with PRA of less than 20%.

CONCLUSION

The HLA-DRB1*15 phenotype is associated with broad RBC and HLA immunization.

Hemolytic disease of the fetus and newborn: managing the mother, fetus, and newborn

Hemolytic disease of the fetus and newborn (HDFN) affects 3/100 000 to 80/100 000 patients per year. It is due to maternal blood group antibodies that cause fetal red cell destruction and in some cases, marrow suppression. This process leads to fetal anemia, and in severe cases can progress to edema, ascites, heart failure, and death. Infants affected with HDFN can have hyperbilirubinemia in the acute phase and hyporegenerative anemia for weeks to months after birth. The diagnosis and management of pregnant women with HDFN is based on laboratory and radiographic monitoring. Fetuses with marked anemia may require intervention with intrauterine transfusion. HDFN due to RhD can be prevented by RhIg administration. Prevention for other causal blood group specificities is less studied.

Society for Maternal-Fetal Medicine (SMFM) Clinical Guideline #8: the fetus at risk for anemia--diagnosis and management

OBJECTIVE

We sought to provide evidence-based guidelines for the diagnosis and management of fetal anemia.

METHODS

A systematic literature review was performed using MEDLINE, PubMed, EMBASE, and the Cochrane Library. The search was restricted to English-language articles published from 1966 through May 2014. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion. Evidence reports and published guidelines were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. GRADE (Grading of Recommendations Assessment, Development, and Evaluation) methodology was used for defining the strength of recommendations and rating the quality of evidence. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence.

RESULTS AND RECOMMENDATIONS

We recommend the following: (1) middle cerebral artery peak systolic velocity (MCA-PSV) measured by ultrasound Doppler interrogation be used as the primary technique to detect fetal anemia; (2) amniotic fluid delta OD450 not be used to diagnosis fetal anemia; (3) MCA-PSV assessment be reserved for those patients who are at risk of having an anemic fetus (proper technique for MCA-PSV evaluation includes assessment of the middle cerebral artery close to its origin, ideally at a zero degree angle without angle correction); (4) if a fetus is deemed at significant risk for severe fetal anemia (MCA greater than 1.5 multiples of the median or hydropic), fetal blood sampling be performed with preparation for an intrauterine transfusion, unless the pregnancy is at a gestational age when the risks associated with delivery are considered to be less than those associated with the procedure; (5) if a fetus is deemed at significant risk for severe fetal anemia, the patient be referred to a center with expertise in invasive fetal therapy; (6) MCA-PSV be considered to determine the timing of a second transfusion in fetuses with anemia, and, alternatively, a predicted decline in fetal hemoglobin may be used for timing the second procedure; and (7) pregnancies with a fetus at significant risk for fetal anemia be delivered at 37-38 weeks of gestation unless indications develop prior to this time.

Haemolytic disease of the fetus and newborn

Haemolytic Disease of the Fetus and Newborn (HDFN) is caused by maternal alloimmunization against red blood cell antigens. In severe cases, HDFN may lead to fetal anaemia with a risk for fetal death and to severe forms of neonatal hyperbilirubinaemia with a risk for kernicterus. Most severe cases are caused by anti-D, despite the introduction of antental and postnatal anti-D immunoglobulin prophylaxis. In general, red blood cell antibody screening programmes are aimed to detect maternal alloimmunization early in pregnancy to facilitate the identification of high-risk cases to timely start antenatal and postnatal treatment. In this review, an overview of the clinical relevance of red cell alloantibodies in relation to occurrence of HDFN and recent views on prevention, screening and treatment options of HDFN are provided.

Intrauterine blood transfusion: current indications and associated risks

Fetal anemia is a serious complication in pregnancy and associated with perinatal mortality and morbidity. During 25 years of worldwide experience with intravascular intrauterine blood transfusion, a variety of indications have been described. Intrauterine transfusion (IUT) treatment is considered most successful for fetal anemia due to red cell alloimmunization. Moreover, the use of this procedure has also been reported in pregnancies with parvovirus B19 infection, fetomaternal hemorrhage and placental chorioangiomas, for example. This review focuses on the current indications of intrauterine blood transfusions. In addition, we describe the potential complications of IUT treatment.

HLA-DRB1 associations in individuals with single and multiple clinically relevant red blood cell antibodies

BACKGROUND

A minority of red blood cell (RBC) alloantigen-exposed persons form antibodies. Responders are at high risk of developing additional antibodies upon subsequent transfusions. Several studies showed an association between particular HLA-DRB1 phenotypes and the development of specific RBC antibodies. This study evaluates the presence of HLA-DRB1 antigens in individuals with single or multiple RBC antibody specificities to explore whether the response against RBC antigens is associated with a summation of particular HLA-DRB1 susceptibility antigens.

STUDY DESIGN AND METHODS

Frequencies of HLA-DRB1 alleles in individuals with antibodies against clinically relevant antigens were compared to a large population cohort to calculate odds ratios (ORs) for alloimmunization to different RBC antigens.

RESULTS

The study cohort consisted of 941 individuals (female-to-male ratio, 3.8) possessing 1462 antibody specificities elicited by transfusion, pregnancy, transplantation, or a combination of these. Besides confirmation of known associations, new associations were identified for anti-E with DRB1*09 and for anti-S with DRB1*07 (ORs, 3.7 and 8.7, respectively). Multiple antibody formation was in a minority of cases associated with the presence of multiple DRB1 susceptibility genes. In multiple responders DRB1*15 was present in almost 40% of cases compared to approximately 25% in single-antibody responders and in the control population.

CONCLUSION

This study suggests that HLA-DRB1 restriction plays an important role for a first RBC antibody response but multiple antibody formation seems less dependent on the presence of particular HLA restriction genes, while HLA-DRB1*15 may represent a susceptibility phenotype enhancing formation of multiple RBC antibody specificities.

Enhancement of Antibody Titre and Development of Additional Red Cell Alloantibodies Following Intrauterine Transfusion

Intrauterine blood transfusion is the mainstay of managing foetuses with severe anemia. It may however result in fetomaternal hemorrhage, which in cases of Rh isoimmunisation may increase the severity of the disease by enhancing the maternal immunological response to fetal antigens. This study was conducted to determine the frequency, specificity and origin of additional red cell antibodies which developed after IUT. The change in the titre of allo anti-D following IUT was also determined. Antibody detection and titration was done on the blood samples of all the patients before and after intrauterine blood transfusion to check for the development of additional antibody and change in the titre of existing anti-D. Severe anemia was found in 17 (58.6 %) fetuses who received a total of 42 ultrasound-guided IUTs. Development of antibodies additional to anti-D in maternal serum was seen in 5 (29.4 %) cases. The specificity of additional alloantibodies was anti-C in four cases whereas it was anti-E in one case. Four fold or greater increase in existing allo-anti D titre was seen in 6 (35.3 %) cases after IUT. Enhancement of maternal sensitisation leading to an increase in maternal antibody titre is particularly seen after the first IUT. Matching of the donor RBCs particularly for Rh antigens might prevent the induction of additional alloantibodies against these antigens. IUT as a treatment modality should be given judiciously and only when the need is inevitable.

Long-Term follow up after intra-Uterine transfusionS; the LOTUS study

BACKGROUND

The Leiden University Medical Center (LUMC) is the Dutch national referral centre for pregnancies complicated by haemolytic disease of the fetus and newborn (HDFN) caused by maternal alloimmunization. Yearly, 20-25 affected fetuses with severe anaemia are transfused with intra-uterine blood transfusions (IUT). Mothers of whom their fetus has undergone IUT for HDFN are considered high responders with regard to red blood cell (RBC) antibody formation. Most study groups report high perinatal survival, resulting in a shift in attention towards short- and long-term outcome in surviving children.

METHODS/DESIGN

We set up a large long-term observational follow-up study (LOTUS study), in cooperation with the Sanquin Blood Supply Foundation and the LUMC departments of Obstetrics, Neonatology and ImmunoHematology & Bloodtransfusion.The first part of this study addresses several putative mechanisms associated with blood group alloimmunization in these mothers. The second part of this study determines the incidence of long-term neurodevelopment impairment (NDI) and associated risk factors in children treated with IUT. All women and their life offspring who have been treated with IUT for HDFN in the LUMC from 1987-2008 are invited to participate and after consent, blood or saliva samples are taken. RBC and HLA antigen profile and antibodies are determined by serologic or molecular techniques. Microchimerism populations are tested by real time polymerase chain reaction (RT PCR).All children are tested for their neurological, cognitive and psychosocial development using standardised tests and questionnaires. The primary outcome is neurodevelopmental impairment (NDI), a composite outcome defined as any of the following: cerebral palsy, cognitive or psychomotor development < 2 standard deviation, bilateral blindness and/or bilateral deafness.

DISCUSSION

The LOTUS study includes the largest cohort of IUT patients ever studied and is the first to investigate post-IUT long-term effects in both mother and child. The results may lead to a change in transfusion policy, in particular future avoidance of certain incompatibilities. Additionally the LOTUS study will provide clinicians and parents better insights in the long-term neurodevelopmental outcome in children with HDFN treated with IUTs, and may improve the quality of antenatal counselling and long-term guidance.

The use of blood products in perinatal medicine

Fetal and neonatal medicine is a field with many new procedures and techniques. An increasing number of centres worldwide give intrauterine transfusions, which are considered to be standard-of-care treatment for severe fetal anaemia. The survival of very prematurely born neonates, in particular of a gestational age of <28 weeks, has greatly improved over the last decade but almost all these children need transfusions. Although in many cases such blood transfusions are life saving, randomized, controlled studies investigating appropriate indications, transfusion volume and type of blood product have not been performed. Most of the protocols used are expert based.

Does an alloimmune response to strong immunogenic red blood cell antigens enhance a response to weaker antigens?

BACKGROUND

It has been suggested that an immune response against the high immunogenic D antigen also augments the immune response to less immunogenic red blood cell (RBC) antigens. Based on the high antibody frequency, E and K antigens can also be regarded as strong immunogens. The question is whether the immunization against E and K antigens also enhances the formation of other antibody specificities. This question is in particular relevant for patients who are currently transfused with RH- and/or K-matched RBCs.

STUDY DESIGN AND METHODS

A retrospective multicenter study analyzed FY, JK, and MNS antibodies alone and in combination with anti-E and/or anti-K. Analysis was performed for primary and subsequent antibody responses.

RESULTS

In the cohort analyzed, 5016 patients possessed 5981 antibodies. Antibodies directed to multiple blood group systems were present in 606 of the 779 (78%) patients with multiple antibodies. In 88 of 1270 (6.9%) patients, FY, JK, and/or MNS antibodies appeared simultaneous with anti-E and/or anti-K during a primary antibody response after transfusion. Patients formed antibodies to antigens in the FY, JK, and MNS systems equally often as first antibodies followed by anti-E or anti-K than as second antibodies after anti-E or anti-K were already present. Patients with anti-E and/or anti-K or with antibodies to antigens in the FY, JK, and/or MNS systems equally often formed additional antibodies during a second antibody response.

CONCLUSION

An immune response against allogeneic RBC antigens defines good responders who readily form antibodies against other antigens. No support was found that the response against strong RBC antigens also enhances the formation against weaker antigens.

Effect of screening for red cell antibodies, other than anti-D, to detect hemolytic disease of the fetus and newborn: a population study in the Netherlands

BACKGROUND

Hemolytic disease of the fetus and newborn (HDFN) is a severe disease, resulting from maternal red cell (RBC) alloantibodies directed against fetal RBCs. The effect of a first-trimester antibody screening program on the timely detection of HDFN caused by antibodies other than anti-D was evaluated.

STUDY DESIGN AND METHODS

Nationwide, all women (1,002 in 305,000 consecutive pregnancies during 18 months) with alloantibodies other than anti-D, detected by a first-trimester antibody screen, were included in a prospective index-cohort study. In a parallel-coverage validation study, patients with HDFN caused by antibodies other than anti-D, that were missed by the screening program, were retrospectively identified.

RESULTS

The prevalence of positive antibody screens at first-trimester screening was 1,232 in 100,000; the prevalence of alloantibodies other than anti-D was 328 in 100,000, of which 191 of 100,000 implied a risk for occurrence of HDFN because the father carried the antigen. Overall, severe HDFN, requiring intrauterine or postnatal (exchange) transfusions, occurred in 3.7 percent of fetuses at risk: for anti-K in 11.6 percent; anti-c in 8.5 percent; anti-E in 1.1 percent; Rh antibodies other than anti-c, anti-D, or anti-E in 3.8 percent; and for antibodies other than Rh antibodies or anti-K, in none of the fetuses at risk. All affected children, where antibodies were detected, were promptly treated and healthy at the age of 1 year. The coverage validation study showed a sensitivity of the screening program of 75 percent. Five of 8 missed cases were caused by anti-c, with delay-induced permanent damage in at least 1.

CONCLUSION

First-trimester screening enables timely treatment of HDFN caused by antibodies other than anti-D, however, with a sensitivity of only 75 percent. A second screening at Week 30 of c- women will enhance the screening program. Severe HDFN, caused by antibodies other than anti-D, is associated with anti-K, anti-c, and to a lesser extent with other Rh-alloantibodies.