Non-anti-D antibodies in red-cell alloimmunization

Maternal red blood cell alloimmunization prevalence in the United States

ABSTRACT

Hemolytic disease of fetus and newborn (HDFN) is a life-threatening disease mediated by maternal alloimmunization to red blood cell (RBC) antigens. Studies of maternal alloimmunization prevalence in the United States lack national data. This study describes prevalence and trends in alloimmunization in pregnancy in the United States. RBC antibodies (abs) were identified in a large, nationwide, commercial laboratory database from 2010 through 2021. The cohort comprised pregnancies for which the year of laboratory collection and patient's state of residence were available. Data were normalized based on US Centers for Disease Control and Prevention estimates of live births and weighted by year and US Census Division. Cochrane-Armitage tests assessed temporal trends of alloimmunization. Of 9 876 196 pregnancies, 147 262 (1.5%) screened positive for RBC abs, corresponding to an estimated prevalence of 1518 of 100 000 pregnancies. Of identified RBC abs, anti-D comprised 64.1% pregnancies (586/100 000). Prevalence of other high-risk RBC abs for HDFN included anti-K (68/100 000) and anti-c (29/100 000). Incidence of all 3 high-risk abs increased from 2010 to 2021 (all P < .001). Among almost 10 million pregnancies in the United States, comprising an estimated 14.4% of all pregnancies, 1.5% screened positive for RBC abs. Almost three-quarters (679/100 000 [74.3%]) of RBC abs identified were high risk for HDFN. Although prevalence of anti-D is difficult to interpret without the ability to distinguish alloimmunization from passive immunity, it remains problematic in HDFN, ranking second only to anti-K in critical titers. Given the sequelae of HDFN, new initiatives are required to reduce the incidence of alloimmunization in patients of reproductive potential.

Current Insights Into K-associated Fetal Anemia and Potential Treatment Strategies for Sensitized Pregnancies

K-associated anemic disease of the fetus and newborn (K-ADFN) is a rare but life-threatening disease in which maternal alloantibodies cross the placenta and can mediate an immune attack on fetal red blood cells expressing the K antigen. A considerably more common disease, D-associated hemolytic disease of the fetus and newborn (D-HDFN), can be prophylactically treated using polyclonal α-D antibody preparations. Currently, no such prophylactic treatment exists for K-associated fetal anemia, and disease is usually treated with intrauterine blood transfusions. Here we review current understanding of the biology of K-associated fetal anemia, how the maternal immune system is sensitized to fetal red blood cells, and what is understood about potential mechanisms of prophylactic HDFN interventions. Given the apparent challenges associated with preventing alloimmunization, we highlight novel strategies for treating sensitized mothers to prevent fetal anemia that may hold promise not only for K-mediated disease, but also for other pathogenic alloantibody responses.

Perinatal risk factors associated with severity of haemolytic disease of the foetus and newborn due to Rhc maternal-foetal incompatibility: A retrospective cohort study

BACKGROUND AND OBJECTIVES

Anti-c is the third red blood cell antibody responsible for haemolytic disease of the foetus and newborn (HDFN) requiring intrauterine transfusion. We aimed to identify risk factors associated with HDFN and severe HDFN due to Rhc maternal-foetal incompatibility.

MATERIALS AND METHODS

A retrospective cohort study was conducted in Paris and the surrounding area (France), between 2013 and 2015. We included mothers and their children managed by the National Reference Centre in Perinatal Hemobiology for alloimmunization and maternal-foetal incompatibility for the Rhc antigen (N = 121). We conducted bivariate analyses to assess a relationship between perinatal factors (e.g., titre and concentration of anti-c antibodies, direct antiglobulin test) and HDFN, its severity and duration.

RESULTS

The incidence of HDFN was 30% (n = 36), including 11% of severe HDFN (n = 13). Seven percent (n = 9) of neonates received at least one transfusion during the first week and 21% (n = 26) after this period until 3 weeks of life. During pregnancy, a concentration ≥7.5 IU/ml and a titre ≥4 and above were associated with HDFN and severe HDFN (p < 0.05). At birth, the high intensity of the quantitative direct antiglobulin test was associated with HDFN and severe HDFN (p < 0.05). A concentration ≥15 IU/ml is the best factor (area under curve [AUC] = 0.78) in predicting HDFN, followed by a titre ≥8 (AUC = 0.76).

CONCLUSION

Anti-c alloimmunization causes neonatal anaemia, which is often belated. Paediatricians have to be aware of these risk factors and organize prolonged monitoring of neonates.

Different Types of Minor Blood Group Incompatibility Causing Haemolytic Disease of Neonates in one of the National Children's Medical Centre in China

Purpose

To review the neonatal cases with different types of minor blood group incompatible haemolytic diseases in China, and to improve the clinical understanding and management.

Materials and Methods

Seven cases from January, 1st, 2013 to December 31st, 2019 were searched out and reviewed retrospectively. All clinical data and laboratory findings were collected.

Results

There were totally seven cases enrolled including three cases of MNS, three of Diego, and one of Kidd combined with Rh, anti-RhE incompatibility. Among the seven cases, two had intrauterine transfusion, two underwent exchange transfusion, five received intravenous immune globulin, five cases developed anaemia, and three of them had transfusion. But among them, only four were found to have positive antibody screening and three were confirmed HDN with antibody types antenatally.

Conclusion

The clinical presentation is diverse. Antibody screening followed by the technique of peak systolic velocity in the fetal middle cerebral artery (MCA-PSV) helps to filter out the severe cases.

Hemolytic Anemia Due To Anti-c Incompatibility in The Newborn Period: A Case Report

Hemolytic disease of the fetus and newborn is a disease that is caused by maternal alloantibodies to the fetus. In the literature, the frequency of hemolytic disease of the newborn due to Rh (D) sensitization decreased inversely with the increase in the use of anti-D gammaglobulin. However, the importance of minor blood group incompatibilities has increased in the etiology. Clinical presentation in patients with minor blood group incompatibility may vary from subclinical hemolysis findings to active hemolysis and hyperbilirubinemia requiring blood exchange. In this case study, we present a patient with hemolytic anemia due to anti-c antibody incompatibility.

Title: Effect of multiple maternal red cell alloantibodies on the occurrence and severity of Hemolytic Disease of the Fetus and Newborn

INTRODUCTION

Antenatal antibody screening in India is focused on the detection of anti-D in RhD-negative mothers. HDFN outcome can also be affected by the presence of antibodies other than anti-D. We planned this study to find the impact of 'anti-D in combination with additional antibodies' on the development and severity of HDFN compared with 'anti-D alone'.

METHODS

This is a retrospective study performed at a referral center in northern India from October 2015 to March 2018. Antibody screening was performed on women with complicated obstetric history. Women with anti-D antibody were included in the study and categorized on the basis of presence of additional antibody (anti-D alone or in combination with other antibody). Various clinical, laboratory & interventional parameters were used to define HDFN and severe HDFN. Perinatal outcome was then compared between the two groups.

RESULTS

A total of 176 women with anti-D antibody were included in the study. Of these, 136 cases (77.3%) had anti-D alone while at least one additional antibody was present in 40 (22.7 %) cases. Most common additional antibodies were anti-C, anti-E and anti-c. After excluding 46 women for various reasons, 130 women were left for final analysis. Approximately 57% and 78% of cases were affected by severe HDFN amongst women with anti-D alone and in combination, respectively. Relative risk of developing severe HDFN was 1.7 times higher in women with additional antibody.

CONCLUSIONS

Patients with combination antibodies were found to have more severe HDFN compared to the ones with anti-D alone.

Blood Donation During Pregnancy Due to Anti-Ku Hemolytic Disease of the Fetus and Newborn

BACKGROUND

Management of pregnancy in patients with Kell-null phenotype can be challenging. The immune systems of these patients form an antibody that is universally reactive against the Kell Blood Group System and can cause hemolytic disease of the fetus and newborn.

METHODS

A 29-year-old woman, pregnant for the first time, developed anti-D and anti-Ku. The mother had to have labor induced when her fetus showed signs of severe anemia, but no compatible blood was available for transfusion. The induction was delayed so that a unit of blood could be collected from the mother.

RESULTS

Due to delayed cord clamping at delivery, the newborn did not have anemia and did not require a transfusion. The remaining blood was frozen for future needs.

CONCLUSION

Blood donation by a pregnant woman for potential transfusion to a newborn with anemia is safe for the mother and fetus, and is possibly the only option in hemolytic disease of the newborn due to a rare antibody.

Antibody-mediated immune suppression by antigen modulation is antigen-specific

Alloantibodies developing after exposure to red blood cell (RBC) alloantigens can complicate pregnancy and transfusion therapy. The only method currently available to actively inhibit RBC alloantibody formation is administration of antigen-specific antibodies, a phenomenon termed antibody-mediated immune suppression (AMIS). A well-known example of AMIS is RhD immune globulin prophylaxis to prevent anti-D formation in RhD- individuals. However, whether AMIS is specific or impacts alloimmunization to other antigens on the same RBC remains unclear. To evaluate the specificity of AMIS, we passively immunized antigen-negative recipients with anti-KEL or anti-hen egg lysozyme (HEL) antibodies, followed by transfusion of murine RBC expressing both the HEL-ovalbumin-Duffy (HOD) and human KEL antigens (HOD × KEL RBC). Significant immunoglobulin G deposition on transfused HOD × KEL RBC occurred in all passively immunized recipients. Complement deposition and antigen modulation of the KEL antigen occurred on transfused RBC only in anti-KEL-treated recipients, whereas HEL antigen levels decreased only in the presence of anti-HEL antibodies. Western blot analysis confirmed the specificity of antigen loss, which was not attributable to RBC endocytosis and appears distinct for the 2 antigens. Specifically, removal of KEL was attenuated by clodronate treatment, whereas loss of HEL was unaffected by clodronate in vivo but sensitive to protease treatment in vitro. Antigen-specific modulation correlated with antigen-specific AMIS, with anti-KEL treated recipients forming antibodies to the HOD antigen and anti-HEL-treated recipients developing antibodies to the KEL antigen. Together, these results demonstrate that passively administered antibodies can selectively inhibit the immune response to a specific antigen.

Efficacy of Antenatal Intravenous Immunoglobulin Treatment in Pregnancies at High Risk due to Alloimmunization to Red Blood Cells

Background

Alloimmunization to red blood cells (RBCs) may result in fetal anemia prior to 20 weeks gestation. The question as to whether early commencement of antenatal treatment with high-dose intravenous immunoglobulins (IVIG) may prevent or at least delay the development of fetal anemia in the presence of alloantibodies to RBCs is highly relevant.

Patients and Results

Here we describe a patient with high-titer anti-K and two other severely affected pregnant women with a history of recurrent pregnancy loss due to high-titer anti-D or anti-D plus anti-C. Early commencement of treatment with IVIG (1 g/kg/week) resulted in prevention of intrauterine transfusion (IUT) in the former two cases, and in a significant delay of development of fetal anemia in the remaining case (26 weeks gestation).

Conclusion

Based on our findings and of previously published cases, early initiation of treatment of severely alloimmunized women with IVIG (1 g/kg/week) could potentially improve the outcome of fetuses at risk.

Predicting anti-Kell-mediated hemolytic disease of the fetus and newborn: diagnostic accuracy of laboratory management

BACKGROUND

There is controversy on critical cut-off values of laboratory testing to select pregnancies at increased risk for anti-Kell-mediated hemolytic disease of the fetus and newborn. Without early detection and treatment, anti-Kell-mediated hemolytic disease of the fetus and newborn may result in progressive fetal anemia, fetal hydrops, asphyxia, and perinatal death.

OBJECTIVE

We aimed to determine the value of repeated anti-Kell titer determination and biological activity measurement using the antibody-dependent cellular cytotoxicity test determination in the management of pregnancies at risk for anti-Kell-mediated hemolytic disease of the fetus and newborn.

STUDY DESIGN

This was a retrospective cohort study of pregnancies with anti-Kell and a Kell-positive fetus, identified from January 1999 through April 2015. Laboratory test results and clinical outcome were collected from the Dutch nationwide screening program and the national reference center for fetal therapy in The Netherlands, the Leiden University Medical Center. Diagnostic accuracy was measured (receiver operating characteristic curves, sensitivity, specificity, positive and negative predictive values) for anti-Kell titers and antibody-dependent cellular cytotoxicity test. The relationship between the titer and antibody-dependent cellular cytotoxicity measurements and the 2 foregoing measurements were computed with a Pearson product-moment correlation coefficient.

RESULTS

In a 16-year unselected cohort, representing screening results of 3.2 million pregnancies resulting in live births in The Netherlands, we identified 1026 Kell-immunized pregnancies. In all, 93 pregnant women had anti-Kell and a Kell-positive child, without other red cell alloantibodies. In all, 49 children (53%) needed intrauterine or postnatal transfusion therapy. The first anti-Kell titer showed already a high diagnostic accuracy with an area under the curve of 91%. The optimal cut-off point for the titer was 4 (sensitivity 100%; 95% confidence interval, 91-100), specificity 27% (95% confidence interval, 15-43), and positive predictive value 60% (49-71%). The antibody-dependent cellular cytotoxicity test was not informative to select high-risk pregnancies. Linear regression showed no significant change during pregnancy, when antibody titer and antibody-dependent cellular cytotoxicity test results were compared with every 2 foregoing measurements (P < .0001).

CONCLUSION

Early determination of the anti-Kell titer is sufficient to select pregnancies at increased risk for hemolytic disease of the fetus and newborn with need for transfusion therapy. If the Kell status of the fetus is known to be positive, a titer of ≥4 can be used to target intensive clinical monitoring.

Anti-K1 (Kell) Antibody Expressed in Maternal Breastmilk: A Case Report of a Neonate with Multiple Intrauterine Transfusions and Postnatal Exposure to Kell Antibody in Maternal Breastmilk

Hemolytic disease of the fetus and newborn is a common consideration in newborn medicine, especially among the jaundiced. Maternal breastmilk provides numerous benefits to the infant, including nutrition and immunologic factors. Here, we present an infant who received three intrauterine transfusions for anemia secondary to anti-K1 (Kell), anti-C, and anti-e antibodies and whose maternal breastmilk tested positive for anti-Kell antibodies. The infant required another transfusion at 4 weeks of life for anemia. We review the pathophysiology of anti-Kell antibodies, the immunology of breast milk, and the intersection of these two topics.

Clinically significant anti-KEL RBC alloantibodies are transferred by breast milk in a murine model

BACKGROUND AND OBJECTIVES

Fetuses affected by maternal RBC alloantibodies may have prolonged anaemia after birth, leading one to question whether maternal alloantibody transfer may occur outside the placenta. In response to a recent publication describing breast milk transfer of clinically significant amounts of maternal antiplatelet IgA antibodies from mother to nursing infant, we hypothesized that maternal RBC alloantibodies may also be capable of being transferred in breast milk.

MATERIALS AND METHODS

The presence and clinical significance of breast milk alloantibody transfer were tested through a series of pregnancy, fostering and transfusion experiments, using a murine model in which transgenic RBCs express the human KEL glycoprotein.

RESULTS

Maternal anti-KEL immunoglobulins, induced through transfusion or pregnancy, were detected in the aqueous phase of breast milk. Further, efficient transfer of maternal anti-KEL IgG and IgA to nursing pups was observed in fostering experiments. The breast milk-acquired alloantibodies were clinically significant in wild-type pups in a transfusion setting, binding to 'incompatible' KEL RBCs and leading to premature clearance from the circulation. Although breast milk-acquired alloantibodies also bound to the RBCs of transgenic KEL-positive fostered pups, no anaemia resulted.

CONCLUSIONS

Taking these murine data in combination with recently published human data of maternal antiplatelet IgA antibodies in breast milk leading to sequelae in some infants, it is theoretically possible that maternal anti-RBC IgA alloantibodies may also be transferred in human breast milk and may lead to sequelae in some infants under some circumstances.

Red Cell Alloimmunization to Rhesus Antigen Among Pregnant Women Attending a Tertiary Care Hospital in Oman

OBJECTIVES

The detection of maternal alloimmunization against red cell antigens is vital in the management of hemolytic disease of the fetus and newborn. We sought to measure the presence of allosensitization to Rhesus D (RhD) antibodies in antenatal women attending a tertiary care hospital and assess the fetal outcome in sensitized women. 


METHODS

We conducted a retrospective review of pregnant Omani women who registered at the Sultan Qaboos University Hospital between June 2011 and June 2013. Pregnant women were tested for ABO blood type and were screened for RhD antigen and antibodies at their first antenatal clinic visit. In women who tested positive for the RhD antibodies, an antibody titer was performed to evaluate the severity of their case.

RESULTS

Data was available on 1,251 pregnant women who were managed and delivered at Sultan Qaboos University Hospital. The prevalence of RhD negative pregnant women was 7.3%. Blood group O was the most common followed by A, B, and AB. The rate of RhD negative alloimmunization was 10%, and anti-D was the most common antibody detected. There were no stillbirths or neonatal deaths. Postnatal transfusion was necessary for only one baby.

CONCLUSIONS

The prevalence of RhD negativity was comparable to other Asian countries. Previous RhD alloimmunization and history of miscarriages were the most common maternal medical history.

Alloimmunization due to red cell antibodies in Rhesus positive Omani Pregnant Women: Maternal and Perinatal outcome

OBJECTIVE

This study is aimed to determine the prevalence of alloimmunization due to antibodies to red blood cell (RBC) antigens (other than rhesus [Rh] antigen) and report the maternal, perinatal, and neonatal outcomes.

MATERIALS AND METHODS

A retrospective review of medical records of all patients with minor RBCs antibodies alloimmunization who were followed and delivered at Sultan Qaboos University Hospital, Oman from June 2011 to June 2013. Maternal characteristics, antibody type, antibody titer in addition to perinatal and neonatal outcomes were reviewed.

RESULTS

There were 1160 patients with Rh positive status in the study. The most common ABO blood group was O, followed by A, B, and AB. We found 33 out of 1160 Rh positive women alloimmunized with minor RBCs antibodies that gave a prevalence of minor RBCs alloimmunization of 2.7%. The most frequent antibody was anti-E 38%, followed by anti-c 17% and anti-kell 17%. 6 of these 33 patients were identified to have significant antibody titer, and two cases showed evidence of fetal anemia. Only one case required an intrauterine blood transfusion. The most common neonatal complication was jaundice in 53%, followed by respiratory distress syndrome in 28%. Two cases complicated by neonatal anemia required a postnatal blood transfusion.

CONCLUSION

Alloimmunization with anti-E, anti-c, and anti-kell were the most common antibodies among the study group. Minor RBCs alloimmunization was an important cause of neonatal morbidity.

Distribution of Kell phenotype among pregnant women in Sokoto, North Western Nigeria

Introduction

Kell antigen is highly immunogenic and is the common cause of antibody production in mismatched blood transfusions, haemolytic transfusion reaction (HTR) and maternal alloimmunization, which causes severe anaemia in neonates. The aim of this study is to determine the prevalence and ethnic variation of the Kell phenotype among pregnant women in Sokoto, Nigeria.

Methods

Kell antigen status of 150 pregnant women aged 18-45 years and mean age 27.19 ±4.69 years attending antenatal clinic in UDUTH Sokoto Nigeria was determined using the conventional tube method and anti-Kell reagents (Lorne Laboratories, UK).

Results

Among the 150 subjects studied, 3 (2.0%) of subjects were positive and 147 (98.0) were negative for K antigen. Of the 150 pregnant subjects; 32 (21.3%) were primigravidae while 118 (78.7%) were multigravidae. Kell phenotype was more prevalent among primigravidae (3.1%) compared to multigravidae (1.7%) women. The distribution of Kell phenotype among the pregnant subjects was compared based on ethnicity. The prevalence of Kell antigen was significantly higher among the Hausa ethnic group (3.2%) compared to other ethnic groups which indicated zero prevalence (p = 0.001). Kell negative phenotype was ≥ 96.8% among all the ethnic groups.

Conclusion

Our observed prevalence of Kell phenotype is consistent with previous studies among Blacks and Asians but significantly lower than values observed in previous studies among Caucasians. We recommend that all pregnant women should be screened for the presence clinically significant red cell antigens including Kell antigen on their first antenatal visit. Kell negative red cell should be routinely provided for all pregnant women and women with child bearing potential to reduce the risk of Kell-associated HDFN. There is need to introduce routine screening of pregnant women for clinically significant red cell antibodies to facilitate the effective management of HDFN as well as prevent HTR. There is also need for sustained health education of pregnant women in the area to encourage early booking for antenatal care.

Risk factors for alloimmunisation in the general patient population

For hospitals providing services to regional populations, difficulties are associated with transferred patients with poorly communicated medical history and a risk of alloimmunisation. Identification of patients at risk would assist in treatment planning. A retrospective study of alloimmunised patients was undertaken, comparing the demographics and diagnoses of this population with a control patient population. A preponderance of diagnoses of Sepsis, Haematological Malignancy, GIT Bleeds and Renal Failure was demonstrated in the alloimmunised population. Consistent with prior studies, RhD negative patients and female patients were over-represented in the study group, which was also on average significantly older.

Prevalence and Specificity of RBC Alloantibodies in Indian Patients Attending a Tertiary Care Hospital

Background. Red blood cell (RBC) alloimmunization results from genetic disparity of RBC antigens between donor and recipients. Data about alloimmunization rate in general patient population is scarce especially from resource limited countries. We undertook this study to determine prevalence and specificity of RBC alloantibodies in patients admitted in various clinical specialties at a tertiary care hospital in North India. Methods. Antibody screening was carried out in 11,235 patients on automated QWALYS 3 platform (Diagast, Loos, France). Antibody identification was carried out with an 11-cell identification panel (ID-Diapanel, Diamed GmbH, Switzerland). Results. The overall incidence of RBC alloimmunization in transfused patients was 1.4% (157/11235), with anti-E being the most common specificity (36.3%), followed by anti-D (16%), anti-c (6.4%), anti-c + E (6.4%), anti-C + D (5.1%), and anti-K (4.5%). The highest incidence of alloimmunization was observed in hematology/oncology patients (1.9%), whereas in other specialties the range was 0.7–1%. Conclusion. As alloimmunization complicates the transfusion outcomes, authors recommend pretransfusion antibody screening and issue of Rh and Kell matched blood to patients who warrant high transfusion requirements in future.

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.

Associations of Rhesus and non-Rhesus maternal red blood cell alloimmunization with stillbirth and preterm birth

BACKGROUND

Although the risks of adverse pregnancy outcomes associated with anti-D antibodies are well-recognized, much less is known concerning alloimmunization with other red blood cell antibodies detected during routine maternal screening. To date, most reports of adverse pregnancy outcomes associated with non-anti-D antibodies have been from small case studies. The aim of this study was to examine the associations of maternal alloimmunization with specific red blood cell antibodies and the risks of preterm birth and stillbirth in the Swedish population.

METHODS

All antibody screening, outcome and covariate data were obtained through linkages of Swedish national health and data registers. Follow-up in these population-based registers was available up to 31 December 2002. The final study sample consisted of 1,022,569 singleton births from 668,952 mothers during 1987-2002.

RESULTS

In total, 1.3% of the 1,022,569 study pregnancies were alloimmunized. In adjusted logistic regression models, compared with having no antibodies, alloimmunization with anti-D, anti-E, anti-C and anti-c was associated with increased risk of both stillbirth and preterm birth. In addition, anti-Kell was associated with increased risk of preterm birth and anti-Lea with increased risk of stillbirth. Compared with firstborn children, risk of preterm birth associated with alloimmunization was greater in subsequent births

CONCLUSIONS

In the largest study to date, alloimmunization with Rhesus, K- and -Lea red blood cell antibodies increased the risk of preterm birth and/or stillbirth. The association of anti-Lea with stillbirth was an unexpected finding. Further study of the consequences of non-anti-D alloimmunization is warranted.

Duffy antigen receptor for chemokine (DARC) polymorphisms and its involvement in acquisition of inhibitory anti-duffy binding protein II (DBPII) immunity

The Plasmodium vivax Duffy binding protein (PvDBP) and its erythrocytic receptor, the Duffy antigen receptor for chemokines (DARC), are involved in the major P. vivax erythrocyte invasion pathway. An open cohort study to analyze DARC genotypes and their relationship to PvDBP immune responses was carried out in 620 volunteers in an agricultural settlement of the Brazilian Amazon. Three cross-sectional surveys were conducted at 6-month intervals, comprising 395, 410, and 407 subjects, respectively. The incidence rates of P. vivax infection was 2.32 malaria episodes per 100 person-months under survey (95% confidence interval [CI] of 1.92-2.80/100 person-month) and, of P. falciparum, 0.04 per 100 person-months (95% CI of 0.007-0.14/100 person-month). The distribution of DARC genotypes was consistent with the heterogeneous ethnic origins of the Amazon population, with a predominance of non-silent DARC alleles: FY*A > FY*B. The 12-month follow-up study demonstrated no association between DARC genotypes and total IgG antibodies as measured by ELISA targeting PvDBP (region II, DBPII or regions II-IV, DBPII-IV). The naturally acquired DBPII specific binding inhibitory antibodies (BIAbs) tended to be more frequent in heterozygous individuals carrying a DARC-silent allele (FY*BES). These results provide evidence that DARC polymorphisms may influence the naturally acquired inhibitory anti-Duffy binding protein II immunity.

Anti Rh Hemolytic Disease due to Anti C Antibody: Is Testing for Anti D Antibodies Enough?

Rh blood group system is a complex blood group system. Rh antibodies are produced in Rh negative individuals following exposure to foreign RBCs after transfusion or pregnancy. Anti C is a rare cause of hemolytic disease of newborn and is very scarcely reported in the literature. The aim of the present case report of Hemolytic disease caused by Anti C antibody is to bring out the fact that antibodies other than anti D should be considered in cases that give a suggestive history but no evidence of Anti D.

Management of fetal hydrops due to maternal antibodies against a low incidence paternal red cell antigen: a novel insight from clinical practice

A rare case of a low incidence red cell antigen causing severe fetal allo-immune red cell disease is presented. Discussion of how this can be diagnosed and successfully managed antenatally using middle cerebral artery Doppler ultrasound and maternal antibody titre levels for fetal surveillance and timing of intervention with intrauterine transfusion.

Frequencies of maternal red blood cell alloantibodies in Port Harcourt, Nigeria

BACKGROUND

Alloantibodies of clinical importance can cause transfusion reactions or hemolytic disease of the fetus and newborn (HDFN). The frequencies of these antibodies have not been reported in our locality.

AIMS

To determine the frequency of occurrence of alloantibodies among pregnant women in Port Harcourt, Nigeria.

SETTINGS AND DESIGN

This is a prospective study, which was carried out in the Braithwaite Memorial Specialist Hospital, Port Harcourt, Nigeria.

MATERIALS AND METHODS

Screening and identification of red blood cell alloantibodies was done on the sera of 500 pregnant women using the DiaMed, DiaCell, and DiaPanel reagents (Cressier, Switzerland). ABO and Rh blood groups were done using antisera bought from Biotec (Ipswich, UK).

RESULTS

Alloantibodies were identified in the serum of 17 of the 500 (3.4%) pregnant women. The specificity of the antibodies was as follows: anti-C 6 (1.2%), anti-E 3 (0.6%), anti-Jsb 3 (0.6%), and anti-K 5 (1.0%). No anti-D was identified despite 8.6% of the study population being Rhesus D (Rh D) negative. The distribution of the antibodies was found to be independent of the blood groups of the participants (χ(2) = 4.050, P = 0.670). Blood group O constituted the highest percentage (48.0%).

CONCLUSION

This study has identified the presence of non-Rh D antibodies to the proportion of 3.4%. Rh D antibody was absent in this population irrespective of the relatively high percentage of Rh D negative women. There is a need to determine the actual risk these antibodies may pose to the antenatal women and to include antibody screening and identification in routine antenatal care.

[Kell immunization--a case report]

INTRODUCTION

The frequency of occurrence of RhD alloimmunization, due to preventive protocols, is decreased in our country, but more often there are other antigens that emerge as a cause of hemolytic disease of fetus. The most prominent is Kell antigen, which promotes specific course of disease based on an innate pathogenetic mechanism. Anti-Kell antibody production is, just as in other atypical antibodies, provoked with transfusion of incompatible blood. Except for the immune-mediated hemolysis, anti-Kell antibodies can also inhibit the function of progenitor (erytroid and megakariocyte) cell lines.

CASE REPORT

We present the case of G1P1 woman in whom a distinct fetal hydrops was sonographically detected in the 28th week of pregnancy. The results of immunological tests undoubtedly pointed to Kell immunization (anti-Kell antibody titer was more than 1:32), and antenatal tests for evaluation of fetal condition (Doppler ultrasound and CTG) clearly showed the severe form of hemolytic disease. We concluded that the fetus was in a hopeless, terminal stage of the disease, and then decided to terminate the pregnancy.

CONCLUSION

The only clinical approach to a problem of Kell alloimunization is active one. Early cordocentesis is recommended as the optimal method for evaluation of fetal condition. The clinical outcome of the fetus will strictly depend on a timely intrauterine transfusion (IUT) procedure. Prophylaxis emerges as a crucial factor in prevention of Kell-alloimmunization. It is to be considered that all females in childhood and throughout the reproductive period should take only K1-negative blood transfusion in order to decrease the incidence of Kell-alloimmunization.

Risk factors for the presence of non-rhesus D red blood cell antibodies in pregnancy

OBJECTIVE

To identify risk factors for the presence of non-rhesus D (RhD) red blood cell (RBC) antibodies in pregnancy. To generate evidence for subgroup RBC antibody screening and for primary prevention by extended matching of transfusions in women <45 years.

DESIGN

Case-control study.

SETTING

Nationwide evaluation of screening programme for non-RhD RBC antibodies.

POPULATION

CASES

consecutive pregnancies (n=900) with non-RhD immunisation identified from 1 September 2002 to 1 June 2003 and 1 October 2003 to 1 July 2004; controls (n=968): matched for obstetric caregiver and gestational age.

METHODS

Data collection from the medical records and/or from the respondents by a structured phone interview.

MAIN OUTCOME MEASURES

Significant risk factors for non-RhD immunisation in multivariate analysis.

RESULTS

Significant independent risk factors: history of RBC transfusion (OR 16.7; 95% CI: 11.4-24.6), parity (para-1 versus para-0: OR 1.3; 95% CI: 1.0-1.7; para-2 versus para-0: OR 1.4; 95% CI: 1.0-2.0; para >2 versus para-0: OR 3.2; 95% CI: 1.8-5.8), haematological disease (OR 2.1; 95% CI: 1.0-4.2), history of major surgery (OR 1.4; 95% CI: 1.1-1.8). For the clinically most important antibodies, anti-K, anti-c and other Rh-nonD-antibodies RBC transfusion was the most important risk factor, especially for anti-K (OR 96.4; 95%-CI: 56.6-164.1); 83% of the K-sensitised women had a history of RBC transfusion. Pregnancy-related risk factors were a prior male child (OR 1.7; 95% CI: 1.2-2.3) and caesarean section (OR 1.7; 95% CI: 1.1-2.7).

CONCLUSIONS

RBC transfusion is by far the most important independent risk factor for non-RhD immunisation in pregnancy, followed by parity, major surgery and haematological disease. Pregnancy-related risk factors are a prior male child and caesarean section. Subgroup screening for RBC antibodies, with exclusion of RhD-positive para-0 without clinical risk factors, is to be considered. This approach will be equally sensitive in detecting severe Haemolytic Disease of the Fetus and Newborn compared with the present RBC antibody screening programme without preselection. Primary prevention by extending preventive matching of transfusions in women younger than 45 will prevent more than 50% of pregnancy immunisations.

Women's attitude towards prenatal screening for red blood cell antibodies, other than RhD

Background

Since July 1998 all Dutch women (± 200,000/y) are screened for red cell antibodies, other than anti-RhesusD (RhD) in the first trimester of pregnancy, to facilitate timely treatment of pregnancies at risk for hemolytic disease of the fetus and newborn (HDFN). Evidence for benefits, consequences and costs of screening for non-RhD antibodies is still under discussion. The screening program was evaluated in a nation-wide study. As a part of this evaluation study we investigated, according to the sixth criterium of Wilson and Jüngner, the acceptance by pregnant women of the screening program for non-RhD antibodies.

Methods

Controlled longitudinal survey, including a prenatal and a postnatal measurement by structured questionnaires. Main outcome measures: information satisfaction, anxiety during the screening process (a.o. STAI state inventory and specific questionnaire modules), overall attitude on the screening program. Univariate analysis was followed by standard multivariate analysis to identify significant predictors of the outcome measures. Participants: 233 pregnant women, distributed over five groups, according to the screening result.

Results

Satisfaction about the provided information was moderate in all groups. All screen- positive groups desired more supportive information. Anxiety increased in screen- positives during the screening process, but decreased to basic levels postnatally. All groups showed a strongly positive balance between perceived utility and burden of the screening program, independent on test results or background characteristics.

Conclusion

Women highly accept the non-RhD antibody screening program. However, satisfaction about provided information is moderate. Oral and written information should be provided by obstetric care workers themselves, especially to screen-positive women.

First report from India of haemolytic disease of newborn by anti-c and anti-E in Rh (D) positive mothers

In India, at the majority of the transfusion centers, antenatal antibody screening is done only in Rh (D) negative mothers. We report here two cases of haemolytic disease of newborn (HDN) by maternal alloimmunization to anti-c in one case, and both anti-c and anti-E in the second case. Both women were Rh (D) positive mothers and HDN was detected postnatally by a positive direct antiglobulin test (DAT) in their newborns. These cases highlight the importance of routine antenatal antibody screening even in Rh (D) positive females. A close follow-up throughout pregnancy is required if irregular antibodies are present so that antigen negative, crossmatch compatible blood can be provided in a timely manner for intra-uterine or exchange transfusions.

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.

Current clinical management of anti-Kell alloimmunization in pregnancy

OBJECTIVES

Few reports have been published of the current clinical management of anti-Kell alloimmunization in pregnancy; its low frequency of occurrence means that the few long series published have covered very ample time periods in which different kinds of clinical management have overlapped. The objective of the present paper is to present our experience in the current clinical management of pregnant women who are positive for the anti-Kell antibody.

STUDY DESIGN

A retrospective analysis was carried out of the case histories of pregnant women who were alloimmunized for the Kell antigen and who were studied and/or treated at the Department of Fetal Medicine in the Virgen de las Nieves University Hospital in Granada (Spain), between 2000 and 2004. The clinical management included the basal measurement of the titre of antibodies, the identification of the paternal phenotype (and that of the fetus, if necessary), the ultrasonographic monitoring of the fetus to detect signs of anaemia, sampling of fetal blood by cordocentesis when fetal anaemia was suspected, and fetal intravascular transfusion when necessary.

RESULTS

Of the 10 pregnancies with anti-Kell antibodies, The Kell antigen was confirmed in the fetus in three cases, in all of which moderate to severe fetal anaemia developed, requiring fetal intravascular transfusions. Although one of the fetus developed antenatal hydrops, a good perinatal result was advised.

CONCLUSIONS

The current approach to anti-Kell alloimmunization enables pregnant women who have Kell-positive fetuses to be treated successfully.

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

OBJECTIVE

Intrauterine transfusion (IUT) is a life-saving therapy for the severely anemic fetus with hemolytic disease. However, maternal additional antibody formation is a complication of the procedure. In this study, we determined antibody formation after introduction of preventive Rh-D, -C, -c, -E, and -e and K matching of IUT donors.

STUDY DESIGN

This was a retrospective follow-up study.

RESULTS

During an 11-year period, 686 Rhesus- and K-matched IUTs were performed in 233 pregnancies and in 95% (652/686) posttransfusion antibody testing was performed after a median interval of 21 days. Twenty-five percent (53/212) of the women formed 64 new antibodies and, compared to our previous study, this incidence was not decreased by the use of Rhesus- and K-matched donors. After delivery, 72% (153/212) of the women had multiple RBC antibodies. Additional antibodies were in 48% (31/64) directed against Rhesus and K antigens, induced by the fetus, or as natural antibodies. In 52% (33/64) the antibodies were directed against non-Rhesus and -K antigens and in 65% (11/17) of eligible cases the IUT donor and not the fetus expressed the corresponding antigen(s).

CONCLUSION

Despite Rhesus- and K-matching, women treated with IUTs still show strikingly broad red cell alloimmunization. More extensive IUT donor red cell matching, including FY, JK, and S antigens, to reduce the formation of new red cell antibodies should be explored.

Use of recombinant erythropoietin for the management of severe hemolytic disease of the newborn of a K0 phenotype mother

Very few people do not express any Kell antigens on their red blood cells (K0 phenotype). They can be immunized by transfusion or pregnancy and develop antibodies against Kell system antigens. These maternal antibodies can cause severe hemolytic disease of the fetus/newborn, as a result of the suppression of erythropoiesis and hemolysis. Multiple intrauterine transfusions in the management of severe hemolytic disease have been shown to cause erythropoietic suppression as well. Recombinant erythropoietin has been successfully used in the management of late anemia of infants with Rh hemolytic disease and in 1 case of KEL1 (Kell)-associated hemolytic disease. The authors present the case of severe hemolytic disease of a newborn due to KEL5 (Ku) isoimmunization of his K0 phenotype mother. Regular intrauterine transfusions were performed to manage the severe fetal anemia (Hb 3 g/dL). A male infant was born at the 36th week of gestation having normal hemoglobin (15.8 g/dL) and developed only mild hyperbilirubinemia. On the 15th day of life, the infant's hematocrit had fallen to 27.3%, with low reticulocyte count and low erythropoietin level. The infant was managed successfully with recombinant erythropoietin.