Non-RhD alloimmunization in pregnancy: an updated review

RhD alloimmunization in pregnancy is still the main cause of hemolytic disease of the fetus and neonate (HDFN). Nevertheless, there are other antigens that may be associated with the occurrence of this phenomenon and that have been growing in proportion, given that current prevention strategies focus only on anti-RhD antibodies. Although not widespread, the screening and diagnostic management of the disease caused by these antibodies has recommendations in the literature. For this reason, the following review was carried out with the objective of listing the main red blood cell antigen groups described - such as Rh, ABO, Kell, MNS, Duffy, Kidd, among others - addressing the clinical importance of each one, prevalence in different countries, and recommended management when detecting such antibodies during pregnancy.

Induced Abortion and the Risk of Rh Sensitization

Importance

While population-level data suggest Rh immunoglobulin is unnecessary before 12 weeks' gestation, clinical evidence is limited. Thus, guidelines vary, creating confusion surrounding risks and benefits of Rh testing and treatment. As abortion care in traditional clinical settings becomes harder to access, many people are choosing to self-manage and need to know if ancillary blood type testing is necessary.

Objective

To determine how frequently maternal exposure to fetal red blood cells (fRBCs) exceeds the most conservative published threshold for Rh sensitization in induced first-trimester abortion.

Design, Setting, and Participants

Multicenter, observational, prospective cohort study using high-throughput flow cytometry to detect circulating fRBCs in paired maternal blood samples before and after induced first-trimester abortion (medication or procedural). Individuals undergoing induced first-trimester abortion before 12 weeks 0 days' gestation were included. Paired blood samples were available from 506 participants who underwent either medical (n = 319 [63.0%]) or procedural (n = 187 [37.0%]) abortion.

Exposure

Induced first-trimester abortion.

Main Outcomes and Measures

The primary outcome was the proportion of participants with fRBC counts above the sensitization threshold (125 fRBCs/5 million total RBCs) after induced first-trimester abortion.

Results

Among the 506 participants, the mean (SD) age was 27.4 (5.5) years, 313 (61.9%) were Black, and 123 (24.3%) were White. Three of the 506 participants had elevated fRBC counts at baseline; 1 of these patients had an elevated fRBC count following the abortion (0.2% [95% CI, 0%-0.93%]). No other participants had elevated fRBC counts above the sensitization threshold after induced first-trimester abortion. The median change from baseline was 0 fRBCs, with upper 95th and 99th percentiles of 24 and 35.6 fRBCs, respectively. Although there was a strong association between the preabortion and postabortion fRBC counts, no other baseline characteristic was significantly associated with postabortion fRBC count.

Conclusions and Relevance

Induced first-trimester abortion is not a risk factor for Rh sensitization, indicating that Rh testing and treatment are unnecessary before 12 weeks' gestation. This evidence may be used to inform international guidelines for Rh immunoglobulin administration following first-trimester induced abortion.

The Rh blood group system and its role in alloimmunization rate among sickle cell disease and sickle thalassemia patients in Iran

INTRODUCTION

The alloimmunization following blood transfusion can be life-threatening. The Rh alloantibodies are one of the most common causes contributing to alloimmunization. This study aimed to evaluate the rate and causes of alloimmunization and to determine the Rh phenotypes and genotypes among sickle cell disease (SCD) and sickle thalassemia (Sβ).

MATERIALS AND METHODS

Our study included 104 SCD and Sβ patients referring to Baghaei 2 Hospital of Ahvaz in 2019 using a non-random simple sampling method. The blood samples were collected for Rh phenotypes, alloantibody screening and identification, and molecular tests. The SSP-PCR and RFLP methods with the Pst 1 enzyme were used.

RESULTS

The alloimmunization rate was 9.6% and 13.2% based on immunohematological tests and medical records, respectively. The main alloantibodies (90%) were anti-Rh, and 40% of the patients had multiple alloantibodies. A significant correlation was found between gender and alloimmunization. The phenotypes of DCce (37.5%), DCcEe (24%), Dce (20.2%), and dce (5.8%) and genotypes of R1r (25%), R1R2 (20.2%), R1R1 (18.3%), and R1R0 (10.6%) were the most prevalent. The R1R2 was a frequent genotype in Sβ.

CONCLUSION

R0r' and R1R0 genotypes were limited to our population in Iran. Due to the differences in RH genotypes between our population and others, the blood transfusion from other ethnicities increased our total alloimmunization rate.

Antenatal and postpartum prevention of Rh alloimmunization: A systematic review and GRADE analysis

BACKGROUND

Existing systematic reviews of Rh immunoprophylaxis include only data from randomized controlled trials, have dated searches, and some do not report on all domains of risk of bias or evaluate the certainty of the evidence. Our objective was to perform an updated review, by including new trials, any comparative observational studies, and assessing the certainty of the evidence using the GRADE framework.

METHODS

We searched MEDLINE, Embase and the Cochrane Library from 2000 to November 26, 2019. Relevant websites and bibliographies of systematic reviews and guidelines were searched for studies published before 2000. Outcomes of interest were sensitization and adverse events. Risk of bias was evaluated with the Cochrane tool and ROBINS-I. The certainty of the evidence was performed using the GRADE framework.

RESULTS

Thirteen randomized trials and eight comparative cohort studies were identified, evaluating 12 comparisons. Although there is some evidence of beneficial treatment effects (e.g., at 6-months postpartum, fewer women who received RhIg at delivery compared to no RhIg became sensitized [70 fewer sensitized women per 1,000 (95%CI: 67 to 71 fewer); I2 = 73%]), due to very low certainty of the evidence, the magnitude of the treatment effect may be overestimated. The certainty of the evidence was very low for most outcomes often due to high risk of bias (e.g., randomization method, allocation concealment, selective reporting) and imprecision (i.e., few events and small sample sizes). There is limited evidence on prophylaxis for invasive fetal procedures (e.g. amniocentesis) in the comparative literature, and few studies reported adverse events.

CONCLUSION

Serious risk of bias and low to very low certainty of the evidence is found in existing RCTs and comparative observational studies addressing optimal effectiveness of Rh immunoprophylaxis. Guideline development committees should exercise caution when assessing the strength of the recommendations that inform and influence clinical practice in this area.

Hemolytic disease of the fetus and newborn due to Rh(D) incompatibility: A preventable disease that still produces significant morbidity and mortality in children

In the mid-20th century, Hemolytic Disease of the Fetus and Newborn, caused by maternal alloimmunization to the Rh(D) blood group antigen expressed by fetal red blood cells (i.e., "Rh disease"), was a major cause of fetal and neonatal morbidity and mortality. However, with the regulatory approval, in 1968, of IgG anti-Rh(D) immunoprophylaxis to prevent maternal sensitization, the prospect of eradicating Rh disease was at hand. Indeed, the combination of antenatal and post-partum immunoprophylaxis is ~99% effective at preventing maternal sensitization to Rh(D). To investigate global compliance with this therapeutic intervention, we used an epidemiological approach to estimate the current annual number of pregnancies worldwide involving an Rh(D)-negative mother and an Rh(D)-positive fetus. The annual number of doses of anti-Rh(D) IgG required for successful immunoprophylaxis for these cases was then calculated and compared with an estimate of the annual number of doses of anti-Rh(D) produced and provided worldwide. Our results suggest that ~50% of the women around the world who require this type of immunoprophylaxis do not receive it, presumably due to a lack of awareness, availability, and/or affordability, thereby putting hundreds of thousands of fetuses and neonates at risk for Rh disease each year. The global failure to provide this generally acknowledged standard-of-care to prevent Rh disease, even 50 years after its availability, contributes to an enormous, continuing burden of fetal and neonatal disease and provides a critically important challenge to the international health care system.

Variant RHD Types in Brazilians With Discrepancies in RhD Typing

BACKGROUND

The knowledge of D variants in patients and donors is important because anti-D alloimmunization can occur in some but not all individuals who express a variant RHD allele. Serologic distinction of RhD discrepancies is not always straightforward, which makes molecular analysis highly desirable.

METHODS

A group of 223 subjects, 129 patients, and 94 blood donors was identified and analyzed on the basis of a D typing discrepancy. The D antigen expression was evaluated by tube and gel hemagglutination with four anti-D reagents. PCR-single specific primer (SSP), multiplex PCR, RHD BeadChip (Immucor), or sequencing were used for molecular analysis.

RESULTS

In total, 168/223 (75%) weak D and 55/223 (25%) partial D variants were identified. Hemagglutination results varied in methods and anti-D reagents used in this process. There was no standard serologic reactivity identified, which could predict what type of D variant would be identified. Among weak D samples, types 1-3 were the most common, while DAR and DVI were most prevalent among partial D samples.

CONCLUSION

Our results show that discrepancies found in the serologic typing should be investigated by molecular methods in order to determine the D variant involved and also to distinguish between weak D and partial D. The knowledge of the distribution of weak D types and partial D among populations is important for D- patients and pregnant women management.

[Spontaneous antepartal RhD alloimmunization]

AIM OF THE STUDY

Assess the incidence of spontaneous antepartal RhD alloimmunization in RhD negative pregnant women with an RhD positive fetus.

DESIGN

Clinical study.

SETTING

Department of Obstetrics and Gynecology, Medical School and University Hospital Olomouc.

METHODS

A total of 906 RhD negative women with an RhD positive fetus and without the presence of anti-Dalloantibodies at the beginning of pregnancy were examined. Always it was a singleton pregnancy, RhD blood group of the pregnant women was assessed in the 1st trimester of pregnancy, RhD status of the fetus was determined after delivery. Screening for irregular antierythrocyte antibodies was performed in all women in the 1st trimester of pregnancy, at 28-32 weeks gestation and immediately prior to delivery at 38-42 weeks gestation. Screening for irregular antierythrocyte antibodies was performed also at 6 months following delivery in all cases of positive antibodies before delivery. Antibody screening was performed using the indirect antiglobulin (LISS/NAT) and enzyme (papain) test with their subsequent identification using a panel of reference erythrocytes by column agglutination method Dia-Med. After delivery, the volume of fetomaternal hemorrhage was assesed in all RhD negative women and RhD alloimmunization prophylaxis was performed by administering the necessary IgG anti-D dose; none of the women were administered IgG anti-D antepartally.

RESULTS

During screening for irregular antierythrocyte antibodies at 28-32 weeks gestation, anti-D alloantibodies were diagnosed in 0.2% of the women (2/906); immediately prior to the delivery at 38-42 weeks gestation, anti-D alloantibodies were diagnosed in 2.3% of the women (21/906) and repeatedly even at 6 months following delivery (21/157). In 82.7% of the women (749/906), examination at 6 months following delivery was not performed, therefore in these women spontaneous antepartal RhD alloimmunization cannot reliably be ruled out. Alloimmunization may not be diagnosed yet at term of delivery. If anti-D alloantibodies were not present prior to the delivery, these women were all administered IgG anti-D in a dose of at least 125 μg after delivery.

CONCLUSION

In RhD negative women with an RhD positive fetus, the incidence of spontaneous antepartal RhD alloimmunization was at least 2.3%. Most cases may theoretically be prevented by prophylactic administration of 250 μg of IgG anti-D to all RhD negative women at 28 weeks gestation.

Reassessing critical maternal antibody threshold in RhD alloimmunization: a 16-year retrospective cohort study

OBJECTIVE

To determine the critical maternal antibody threshold for specialist referral in cases of RhD alloimmunization.

METHODS

This was a retrospective cohort study, covering a 16-year period at the national tertiary fetal medicine center for management of alloimmunization. Data concerning RhD alloimmunized pregnant women were extracted from an institutional database and maternal anti-D antibody levels were cross-checked with the national reference laboratory. Fetal hemoglobin (Hb) levels were determined only at the first intrauterine transfusion (IUT) and were compared with the pretransfusion maternal anti-D antibody level (IU/mL). Sensitivity, specificity and positive and negative predictive values of maternal antibody thresholds for detecting moderate to severe (Hb ≤ 0.64MoM) fetal anemia were calculated.

RESULTS

Between 1996 and 2011, 66 women underwent a first IUT for RhD alloimmunization at our institution. The highest serum anti-D antibody level was extracted for 208 RhD alloimmunized women who did not require IUT during the last 10 years of the study period. The traditional maternal antibody threshold of > 15 IU/mL failed to detect 20% of cases of moderate to severe fetal anemia. The ≥ 4 IU/mL threshold had 100% sensitivity but a 45% false-positive rate. The optimal anti-D antibody threshold for specialist referral in our population was ≥ 6 IU/mL; at this level, no case of moderate to severe anemia was missed and specificity was 61%. Use of this threshold would have eliminated 10% of referrals to our fetal medicine unit without compromising fetal outcomes.

CONCLUSIONS

Setting the critical maternal RhD antibody level at >15 IU/mL does not provide sufficient sensitivity. The lower threshold of ≥ 4 IU/mL, though sensitive, is associated with a 45% false-positive rate. In our population, a threshold of ≥ 6 IU/mL minimizes false-positive referrals while maintaining 100% sensitivity for moderate to severe fetal anemia.

Incidence of maternal sensitisation to Rh(D) in Christchurch, New Zealand and reasons for prophylaxis failures

AIM

To estimate the current incidence of maternal sensitisation to Rh(D) and examine reasons for prophylaxis failures.

METHOD

Retrospective chart review of new sensitisations to Rh(D) detected in antenatal records, between 2005 and 2012 in Christchurch, New Zealand and systematic examination of circumstances likely to have caused prophylaxis failures.

RESULTS

Fifty-four new sensitisations in an at-risk population of about 4624 in 8 years means an incidence of roughly 1.1%. In 86.6% of 45 sensitisations where information was available, there was a recognised sensitising event including previous deliveries while in 13.3% there were none. Of those with recognised sensitising events, 46.1% had anti-D prophylaxis per local guidelines, in 12.8%, prophylaxis was given though it did not conform, entirely, to guideline. No prophylaxis at all was given to 41% despite a sensitising event being recognised.

CONCLUSION

The incidence of maternal sensitisation to Rh(D) in Christchurch, New Zealand, is as expected given our prophylaxis regimen. Half the sensitisations were associated with complete or partial failure to follow local guidelines. Better adherence to this may reduce incidence of sensitisation. It is also thrice as high as might be expected with a routine antenatal anti-D prophylaxis (RAADP) program. An economic analysis of RAADP in New Zealand will be useful.

[Anti-D isoimmunization severe in a twin pregnancy. Case report]

Perinatal hemolytic disease occurs secondary to a hemolytic phenomenon of immune origin resulting in fetal or neonatal anemia. A 38-year-old pregnant woman was referred to the Department of high risk Obstetrics, Hospital Universitario La Paz Madrid because of presenting a dichorionic diamniotic twin pregnancy spontaneously, pre-pregnancy diabetes poorly controlled and severe alloinmunization anti-D. Her first pregnancy ended in a normal delivery at term; in the period of 4 years, she has three newborn with 36, 34 and 40 weeks respectively, who die with a week of life. After that, two intrauterine fetal death occur at 26 weeks of gestation. The patient who is RhD negative, suffers anti-D inmunization with a antibody titration of 1/1024 with 14 weeks of gestation. Twelve plasmapheresis, eight doses of anti-D inmunoglobulins and intrauterine transfusions has been the treatment received. A severe anemia is found during the ultrasound control of the middLe cerebral artery peak systolic velocity in both twins since the 16th week. It remains stable thanks to the treatment. Finally at the 28th week of gestation, pregnancy is terminated with a cesarean section. The twins are born alive and premature, but with good general state. The measurement of the middle cerebral artery peak systolic velocity predicts moderate-severe fetal anemia cases, which are the most important in the clinical management because of the need of active treatment or finish the pregnancy.

Constructing a population-based research database from routine maternal screening records: a resource for studying alloimmunization in pregnant women

Background

Although screening for maternal red blood cell antibodies during pregnancy is a standard procedure, the prevalence and clinical consequences of non-anti-D immunization are poorly understood. The objective was to create a national database of maternal antibody screening results that can be linked with population health registers to create a research resource for investigating these issues.

Study Design and Methods

Each birth in the Swedish Medical Birth Register was uniquely identified and linked to the text stored in routine maternal antibody screening records in the time window from 9 months prior to 2 weeks after the delivery date. These text records were subjected to a computerized search for specific antibodies using regular expressions. To illustrate the research potential of the resulting database, selected antibody prevalence rates are presented as tables and figures, and the complete data (from more than 60 specific antibodies) presented as online moving graphical displays.

Results

More than one million (1,191,761) births with valid screening information from 1982–2002 constitute the study population. Computerized coverage of screening increased steadily over time and varied by region as electronic records were adopted. To ensure data quality, we restricted analysis to birth records in areas and years with a sustained coverage of at least 80%, representing 920,903 births from 572,626 mothers in 17 of the 24 counties in Sweden. During the study period, non-anti-D and anti-D antibodies occurred in 76.8/10,000 and 14.1/10,000 pregnancies respectively, with marked differences between specific antibodies over time.

Conclusion

This work demonstrates the feasibility of creating a nationally representative research database from the routine maternal antibody screening records from an extended calendar period. By linkage with population registers of maternal and child health, such data are a valuable resource for addressing important clinical questions, such as the etiological significance of non-anti-D antibodies.

Development of a transparent interactive decision interrogator to facilitate the decision-making process in health care

BACKGROUND

Decisions about the use of new technologies in health care are often based on complex economic models. Decision makers frequently make informal judgments about evidence, uncertainty, and the assumptions that underpin these models.

OBJECTIVES

Transparent interactive decision interrogator (TIDI) facilitates more formal critique of decision models by decision makers such as members of appraisal committees of the National Institute for Health and Clinical Excellence in the UK. By allowing them to run advanced statistical models under different scenarios in real time, TIDI can make the decision process more efficient and transparent, while avoiding limitations on pre-prepared analysis.

METHODS

TIDI, programmed in Visual Basic for applications within Excel, provides an interface for controlling all components of a decision model developed in the appropriate software (e.g., meta-analysis in WinBUGS and the decision model in R) by linking software packages using RExcel and R2WinBUGS. TIDI's graphical controls allow the user to modify assumptions and to run the decision model, and results are returned to an Excel spreadsheet. A tool displaying tornado plots helps to evaluate the influence of individual parameters on the model outcomes, and an interactive meta-analysis module allows the user to select any combination of available studies, explore the impact of bias adjustment, and view results using forest plots. We demonstrate TIDI using an example of a decision model in antenatal care.

CONCLUSION

Use of TIDI during the NICE appraisal of tumor necrosis factor-alpha inhibitors (in psoriatic arthritis) successfully demonstrated its ability to facilitate critiques of the decision models by decision makers.

Serologic and molecular characterization of D variants in Brazilians: impact for typing and transfusion strategy

Rh discrepancies are a problem during routine testing because of partial D or weak D phenotypes. Panels of monoclonal antibodies (MoAb) are being developed to identify D variants such as partial D and weak D when there are anomalous D typing results; however, molecular characterization offers a more specific classification of weak and partial D. The weak D and partial D phenotypes are caused by many different RHD alleles encoding aberrant D proteins, resulting in distinct serologic phenotypes and the possibility of anti-D immunization. We evaluated currently used serologic methods and reagents to detect and identify D variants and correlated the results with molecular analyses. A total of 306 blood samples from Brazilian blood donors and patients with discrepant results in routine D typing were analyzed. In total, 166 (54.2%) weak D, 136 (44.4%) partial D, 3 (1%) DEL, and 1 (0.3%) DHAR variants were identified. Among weak D samples, 76 weak D type 1 (45.8%), 75 weak D type 2 (45.2%), 13 weak D type 3 (7.8%), and 2 weak D type 5 (1.2%) alleles were found. Among the partial D samples, 49 type 4.0 weak partial D (36%), 9 DAR (6.6%), 24 DFR (17.6%), 6 DBT (4.4%), 1 DHMi (0.73%), 26 DVI (19%), 14 DVa (10.3%), 5 DIVb (3.7%), and 2 DVII (1.5%) were observed. Two samples identified as DEL by adsorption-elution were characterized by molecular analyses as RHD(IVS5–38DEL4) and one sample was characterized as RHD(K409K). One sample was characterized as DHAR, a CE variant positive with some monoclonal anti-D. Our results showed that the use of different methods and anti-D reagents in the serologic routine analysis revealed D variants that can be further investigated. Molecular methods can help to differentiate between partial D and weak D and to characterize the weak D types, providing additional information of value in the determination of D phenotypes. This distinction is important for optimized management of D– RBC units and for the prevention of anti-D–related hemolytic disease of the fetus and newborn.

Laboratory methods for Rh immunoprophylaxis: a review

The recommended dose of Rh immune globulin for postpartum Rh immunoprophylaxis is based on an estimation of the volume of the fetomaternal hemorrhage, if any, measured as the percent of fetal RBCs in a sample of the D– mother's blood. Laboratory methods for distinguishing fetal from maternal RBCs have been based on their different blood types (D+ versus D–) or predominant hemoglobin content (hemoglobin F versus hemoglobin A). We conducted a review of the medical literature describing laboratory methods for detecting and quantifying fetal RBCs in maternal blood samples. We also used data collected for the College of American Pathologists Fetal RBC Detection Surveys to determine which laboratory methods are used currently in hospitals in the United States. The rosette screen is used widely for identifying D– mothers who may require additional doses of Rh immune globulin for postpartum immunoprophylaxis. As the rosette screen targets the D antigen, it is not suitable for detecting a fetomaternal hemorrhage in D+ mothers or when the D type of the fetus or newborn is D– or unknown. The acid-elution (Kleihauer- Betke) assay is a sensitive laboratory method for quantifying a fetomaternal hemorrhage, but it is tedious, often inaccurate, and difficult to reproduce. Flow cytometry, using anti-D or anti-hemoglobin F reagents, offers a more precise quantification of fetal RBCs in maternal blood. However, flow cytometry services for this function are available in relatively few hospital laboratories in the United States because of logistic and fiscal impediments.

[The importance of laboratory diagnosis in allo-immunization through pregnancy and hemolytic disease of the newborn]

BHNN is an affection in which life duration of fetus red cells is decreased by means of maternal antibodies opposing certain antigens inherited from the father.The present study will prove the importance of laboratory tests in the diagnosis of alloimmunization through pregnancy and BHNN.

MATERIAL AND METHOD

Laboratory determinations were performed between March 2008 and February 2009 on samples from 187 Rh negative pregnant female with incompatible pregnancy and Rh D positive newborns; there was used a certain algorithm for and identifying.

RESULTS

After applying the proposed algorithm, 4.2% of the cases were discovered to be immunized, whereas 2.6% of the cases were BHNN. As the specificity of irregular antibodies involved, 62.5% were anti D, 25% anti Kell and 12.5% anti E. The results show the fact that the incidence of these pathological entities is far more extended than in other countries.

CONCLUSIONS

Owing to the fact that alloimmunization by pregnancy and BHNN is still a frequent phenomenon, an attentive supervision is very important both for preparing the patient and the medical team aiming to prevent perinatal morbidity.

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.

[Frequencies of blood groups, ABO and Rh D incompatibility in post-delivery women and their liveborn]

OBJECTIVE

This study aimed to assess the frequency of different blood phenotypes and to predict the risk of Rh D alloimmunization and maternal-fetal incompatibility in a Brazilian population living in the West zone of the city of São Paulo-Brazil.

METHODS

This descriptive study evaluated 2,372 post-delivery women and their liveborn during one year. Blood types were analyzed by means of tube agglutination tests.

RESULTS

The blood type frequencies were: 50.67 O, 32.17 A, 13.45 B, 3.75 AB, 90.34 Rh D(+) and 9.66 Rh D(-). ABO maternal-fetal incompatibility was detected in 18.4% and Rh D incompatibility in 7%.

CONCLUSION

The fraction of Rh D(-) population at high risk for Rh D alloimmunization was 82%, emphasizing the importance of Rh D alloimmunization profilaxis.

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.

Fetal Intravenous Immunoglobulin Therapy in Rhesus Hemolytic Disease

Intrauterine blood transfusion is the mainstay of treatment of fetal rhesus hemolytic anemia with optimal perinatal outcome. Postnatal immunoglobulin therapy has been successfully used in the management of alloimmunized neonates and has shown to decrease the need for exchange transfusion. We report the first case series of fetal immunoglobulin therapy in the antenatal management of severe Rh incompatibility.

Alloimmunity to RhD in humans

The RhD protein is expressed only on human red blood cells (RBC), and is one of the most immunogenic of the blood groups. It is of clinical importance since the alloantibody (anti-D) can hemolyse D positive RBC after blood transfusion, or cause hemolytic disease of the newborn. The immunogenicity of D is better understood with the knowledge of the genetic basis of the protein(s) involved, the molecular orientation in the RBC membrane, and the nature of the cellular immune response to proteins. The adaptive humoral response consists of antigen presenting cells, T-cells and B-cells, which interact cooperatively to result in antibody against the antigen in question. The anti-D that B-cells produce is targeted against surface membrane determinants (B-cell epitopes) and are conformational i.e. non-contiguous amino acids. The antigen specific T-cells recognize short linear peptides in the context of MHC class II, and these T-cell epitopes can reside anywhere in the protein. Since the RhD protein in D-positive individuals differs by some 35 amino acids from the RhCcEe protein in D-negative individuals, the opportunity for generating immunogenic T-cell epitopes is much greater than that for alleles characterized by a single amino acid difference e.g. E and e. Multiple conformational B-cell epitopes are also created by the presence of several D-specific amino acids in extracellular loops on the red cells surface, which may stimulate several B-cell clones and develop a strong polyclonal antibody response. With greater understanding comes the possibility of manipulating the immune response to D in clinical situations.

[Alloimmunization to a high frequency Rh antigen]

We report the case of a pregnant woman sensitized with a panreactive anti-Rh17 alloantibody. Patient's red blood cells showed a partial deletion of Rh antigens, which was responsible for the alloimmunization. An autotransfusion program was instrumented so as to cover possible demands. Molecular analysis of the RH locus showed the presence of a hybrid RHCE-D(5-7)-CE allele that gave origin to the deleted phenotype.

Secondary anti-D immunization by Del red blood cells

BACKGROUND

Recent molecular studies of the RHD gene have revealed that D(el) individuals retain a grossly intact RHD gene or have a portion of RHD in their genomes. No D(el) phenotype has yet been shown to induce a primary or secondary alloanti-D immunization, however.

CASE REPORT

A 67-year-old D- Japanese woman with a history of allosensitization from transfusion of D+ red blood cells (RBCs) was negative for anti-D at admission. After she received RBCs from 19 apparently D- donors, she developed anti-D with an 8-fold titer. The titer of anti-D increased further to 128-fold after transfusions of cross-match-compatible D- negative RBCs from 40 donors over the next 2 years. Two of 59 donors were found to be RHD gene-positive and antigen D- with a D(el) phenotype, that is, RHD(K409K).

CONCLUSION

This is the first case in which RBCs having the D(el) phenotype induced a secondary alloanti-D immunization. A D- donor with the RHD(K409K) allele was associated with the development of anti-D. Adverse episodes or evidence of hemolysis was not observed after the transfusion of RHD(K409K) RBCs. Further clinical evidence is needed to reveal whether the D(el) phenotype has a clinically relevant potential for anti-D immunization.

Novel weak D types 31 and 32: adsorption-elution-supported D antigen analysis and comparison to prevalent weak D types

BACKGROUND

Weak D types are thought to express rather quantitative than qualitative D antigen variants. Distinct type-specific phenotypes and weak D cases with anti-D alloimmunization, however, suggest a variable degree of D antigen alteration.

STUDY DESIGN AND METHODS

Variant D types were investigated by use of molecular typing, RHD sequencing, extended serologic D antigen investigations, and flow cytometric D antigen density determination.

RESULTS

Two novel weak D types were discovered, termed weak D type 31 and 32 with single RHD nucleotide substitutions coding for amino acid exchanges in predicted intracellular RhD polypeptide stretches, with antigen densities of approximately 130 and 50 D sites per red blood cell, respectively. Adsorption-elution technique-supported D epitope mapping of these two weak D types, the recently described weak D type 26, and of the most common Central European weak D types (weak D types 1, 2, 3, 4.0, and 4.1) demonstrated the expression of all tested D epitopes. In contrast, a distinct D epitope loss was detected in weak D type 15 and partial D control samples.

CONCLUSION

All novel and prevalent weak D types expressed all tested D epitopes. Our results indicate that adsorption-elution techniques may be of advantage whenever D epitope loss is suspected in extremely weak D variants.

Partial D, weak D types, and novel RHD alleles among 33,864 multiethnic patients: implications for anti-D alloimmunization and prevention

BACKGROUND

The D antigen includes category D, partial D, and weak D types, which are important because anti-D alloimmunization can occur in some but not all persons that express a variant RHD allele. At present, there is little prospective information on the prevalence of D variants among obstetric patients and potential transfusion recipients.

STUDY DESIGN AND METHODS

The RHD alleles were prospectively examined in a large patient population identified on the basis of a difference in anti-D reactivity between two reagents.

RESULTS

Fifty-five discrepancies (0.96% of D-) were noted among 33,864 ethnically diverse patients over 18 months, of which 54 represented mutated RHD alleles. Seven obstetric patients were assigned D- status based on serology; only 1 patient had a partial RHD allele. Ten of 25 (36%) obstetric patients and 4 of 6 (67%) female potential transfusion recipients of childbearing age or younger were assigned D+ status, and they expressed a D variant known to permit anti-D alloimmunization. In total 20 RHD alleles were identified including category, DVa or DVa-like alleles (n = 7), DAR (n = 8), and four novel RHD alleles including two new DAU alleles.

CONCLUSION

Given the complexity of D antigen expression, it is concluded that some clinically important D variants identified by standard serologic analysis phenotype as D+ and are potentially at risk for the development of anti-D.

Specificity and isotype of Rh specific antibodies produced by human B-cell lines established from alloimmunized Rh negative women

Despite the successful outcome of anti-D prophylaxis program, alloimmunization still occurs. The aim of this study was to examine the specificity and isotype of anti-Rh antibodies in plasma samples of Rh negative alloimmunized individuals and to study the same parameters in lymphoblastoid cell lines (LCLs) generated from the same donors. Specificity of anti-Rh antibodies was determined in plasma of nine alloimmunized subjects by direct hemagglutination using a panel of known RBC genotypes and isotype of specific antibodies were identified by an antigen specific ELISA. Similar methods were employed to determine specificity and isotype of antibodies produced by Rh specific LCLs established from four donors. LCLs were generated by Epstein-Barr virus transformation of peripheral blood mononuclear cells isolated from each donor followed by their culture over a feeder of human fetal fibroblasts. Upon emergence of lymphoblastoid cells, culture supernatants were assayed for presence of Rh specific antibody by hemagglutination assay. Anti-D was the predominant antibody in both plasma samples and among the 128 established LCLs; however, antibodies to other Rh specificities namely C and E were also produced. The isotype of anti-Rh antibody in all plasma samples was found to be IgG, predominantly IgG1, combined in 7 samples with IgM. Similarly 76%, 9.2% and 14.8% of LCLs were determined to produce antibody of IgG, IgM and of both isotypes, respectively. The data supported that the D antigen is the immunodominant component of the Rh system as indicated by the in vitro and in vivo profiles of Rh specificities in our alloimmunized subjects.

Red Blood Cell Alloimmunization in Pregnancy

Red blood cell (RBC) alloimmunization in pregnancy continues to occur despite the widespread use of both antenatal and postpartum Rhesus immune globulin (RhIG), due mainly to inadvertent omissions in administration as well as antenatal sensitization prior to RhIG given at 28 weeks' gestation. Additional instances are attributable to the lack of immune globulins to other RBC antigens. Evaluation of the alloimmunized pregnancy begins with the maternal titer. Once a critical value [32 for anti-Rh(D) and other irregular antibodies; 8 for anti-K and -k] is reached, fetal surveillance using serial Doppler ultrasound measurements of the peak velocity in the fetal middle cerebral artery (MCA) is standard. In the case of a heterozygous paternal phenotype, amniocentesis can be performed to detect the antigen-negative fetus that requires no further evaluation. MCA velocities greater than 1.5 multiples of the median necessitate cordocentesis, and if fetal anemia is detected, intrauterine transfusion therapy is initiated. A perinatal survival of greater than 85% with normal neurologic outcome is now expected. Future therapies will target specific immune manipulations in the pregnant patient.

[Foetomaternal erythrocyte incompatibilities: from immunohaematologic surveillance of pregnant women to haemolytic disease of the newborn]

Despite the generalization of prevention measures against foetomaternal alloimmunization with anti-D immunoprophylaxis since 1970s, retrospectively 30 years later, its complications (new-born child's severe haemolytic disease, foetal death by anemia or nuclear icterus by bilirubin encephalopathy) have not disappeared. At the same time, alloimmunizations against antigens other than D increase with no possible prevention. As part of the set up in France of regional files analysing and making an inventory of serious foetomaternal incompatibilities requiring in utero or neonatal transfusion, we felt the need to synthesize current data, biological profiles (early screening of erythrocytic alloimmunization and its follow up during pregnancy, father's immunohaematologic status, evaluation of in utero immune haemolysis and impact of new non invasive techniques of diagnosis-RH1 foetal genotypage from ADN foetal of RH1--mothers' maternal plasma), clinical and paraclinical data (evaluation of foetal haemolysis by echography, recording of foetal movements and foetal cardiac rhythm), therapeutic indicators (in utero foetal transfusions or exsanguinotransfusions, neo and postnatal transfusions or exsanguinotransfusions, induced premature labour, newborn's intensive continue phototherapy and Rhesus immunoprophylaxis) in order to enable medical and paramedical professionals to carry out the specific supervision of pregnancies with foetomaternal incompatibility, the in utero, neo- and postnatal treatment of child and the efficient therapeutic prevention of anti-D alloimmunization, in a cooperative way.

[Doppler ultrasound to detect Rh: a systematic review]

BACKGROUND

Red cell alloimmunization is an important cause of perinatal morbidlity and mortality. Invasive procedures used to diagnose fetal anemia are associated with serious fetal and maternal complications. The development of noninvasive techniques as Doppler ultrasound can help us in the fetal anemia diagnosis.

OBJECTIVES

To evaluate the effect of the Doppler ultrasound in prediction of fetal anemia caused by red cell alloimmunization. Strategy search: Relevant studies were identified by reviewing the registry of COCHRANE, and OVID, PROQUEST, MEDLINE and EMBASE data bases from 1966 to 2004.

SELECTION CRITERIA

All prospective studies with clinically relevant results with comparison of Doppler ultrasound in fetal umbilical artery, fetal descendent aorta, middle cerebral fetal artery or esplecnic fetal artery with hemoglobin or fetal hematocrit.

DATA COLLECTION AND ANALYSIS

Data were extracted from each report. The quality revision of the studies and the data compilation were made by the reviewers.

MAIN RESULTS

Eighteen articles were included. Two studies reached the level of evidence 1 for diagnostic tests. The diagnostic tests had variations depending on the different cut-off of each study. Studies with level 1 of evidence reported detection of 100% for moderate to severe fetal anemia.

CONCLUSIONS

Implementation of Doppler ultrasound for prediction of fetal anemia in complicated pregnancies with alloimmunization could reduce the number of invasive procedures and therefore its complications. The level of present evidence reveals to us that the studies do not fulfill the criteria of methodological quality.

Risk factors for alloimmunization by patients with sickle cell disease

Blood transfusion in patients with sickle cell disease (SCD) is limited by the development of alloantibodies to erythrocytes. In the present study, the frequency and risk factors for alloimmunization were determined. Transfusion records and medical charts of 828 SCD patients who had been transfused and followed at the Belo Horizonte Blood Center, Belo Horizonte, MG, Brazil, were retrospectively reviewed. Alloimmunization frequency was 9.9% (95% CI: 7.9 to 11.9%) and 125 alloantibodies were detected, 79% of which belonged to the Rhesus and Kell systems. Female patients developed alloimmunization more frequently (P = 0.03). The median age of the alloimmunized group was 23.3 years, compared to 14.6 years for the non-alloimmunized group (P < 0.0001). Multivariate analyses were applied to the data for 608 hemoglobin (Hb) SS or SC patients whose number of transfusions was recorded accurately. Number of transfusions (P = 0.00006), older age (P = 0.056) and Hb SC (P = 0.02) showed independent statistical associations with alloimmunization. Hb SC patients older than 14 years faced a 2.8-fold higher (95% CI: 1.3 to 6.0) risk of alloimmunization than Hb SS patients. Female Hb SC patients had the highest risk of developing alloantibodies. In patients younger than 14 years, only the number of transfusions was significant. We conclude that an increased risk of alloimmunization was associated with older patients with Hb SC, specially females, even after adjustments were made for the number of transfusions received, the most significant variable.

On a much higher than reported incidence of anti-c in R1R1 patients with anti-E

A previous study involving tube IATs, untreated RBCs, and a low ionic-strength additive reagent revealed that approximately one-third of R(1)R(1) patients with anti-E have a concomitant anti-c. However, the current study finds a much higher incidence of anti-c in such patients, using gel technology in conjunction with ficin-pretreated RBCs. Results of antibody identification studies and transfusion records of 82 R(1)R(1) patients with anti-E were reviewed. Serologic test methods included a LISS wash solution for tube IATs (15 min at 37 degrees C, anti-IgG), ficin-tube IATs (30 min at 37 degrees C, anti-IgG + anti-C3), and gel IATs (untreated or ficin-treated RBCs or both, anti-IgG gels). LISS-tube or gel IATs with untreated RBCs revealed anti-c in 32 patients with anti-E. When gel-IAT and ficin-pretreated RBCs were used, 21 additional patients with anti-E were found to have anti-c. In samples from 26 R(1)R(1) patients with anti-E, anti-c was not demonstrable by ficin-gel IATs, and in 3 cases, the ficin-gel tests were inconclusive. In five cases in which E- RBCs not tested for c antigen were transfused to patients found by ficin-gel IAT to be without anti-c, all subsequently performed crossmatches with E-, c-untested RBCs were compatible. The incidence of anti-c in R(1)R(1) patients with anti-E in this study was 32 of 82 (39%) with untreated RBCs and 53 of 82 (65%) when the ficin gel data were included. The latter is significantly higher than the 32 percent incidence previously reported (p = 0.0001). Accordingly, all patients at our facility with an Rh antibody are now tested for those additional Rh antibodies they can make, as predicted from their Rh phenotype. The data from this study strongly support the selection of R(1)R(1) RBCs for all c- patients with anti-E.

Hydrops fetalis caused by homozygous alpha-thalassemia and Rh antigen alloimmunization: report of a survivor and literature review

Hematologic causes of hydrops fetalis include homozygous alpha-thalassemia and immune hemolytic anemias. We report the case of a boy with hydrops fetalis who had homozygous alpha-thalassemia and alloimmune hemolytic anemia due to anti-E and anti-C blood group antibodies. He received intrauterine red blood cell transfusions and postnatal chronic transfusion with iron chelation therapy. A non-myeloablative sibling stem cell transplant failed. He is now 5 years and 6 months of age, hypothyroid with short stature, but in overall good health. He is one of the oldest reported homozygous alpha-thalassemia survivors and, to our knowledge, the only survivor with immune- and nonimmune-induced hydrops fetalis.

Maternal ABO-mismatched blood for intrauterine transfusion of severe hemolytic disease of the newborn due to anti-Rh17

BACKGROUND

Clinically significant antibodies to high-incident antigens present a challenge in hemolytic disease of the newborn. Antigen-negative blood may be difficult to obtain for intrauterine transfusion (IUT). In these instances, maternal blood is de facto compatible regardless of an ABO mismatch.

CASE REPORT

A group B/D-- woman with a history of hemolytic disease of the newborn due to anti-Rh17 (titer 256) presented to the obstetrical clinic at 12 weeks gestation for management of her third pregnancy. She consented to donate blood for possible IUT.

STUDY DESIGN AND METHODS

Washed maternal packed cells were suspended in saline to 75 percent Hct and irradiated before transfusion. The fetus was transfused via the intrahepatic vein.

RESULTS

Ultrasound examination at 19 weeks indicated a hydropic fetus. The fetal blood group was O Rh+, direct antiglobulin test 4+, and hemoglobin 22 g per L. A total of 368 mL of maternal blood was transfused during seven procedures. Labor was induced at 38 weeks, and a 2560-g male infant was delivered by Caesarian-section due to fetal distress. The infant grouped as B Rh+, direct antiglobulin test negative. No group O red blood cells were detected. The hemoglobin level was 143 g per L rising to 209 g per L at discharge 3 days later. The indirect bilirubin was 55 micromol/L and remained stable during the hospital stay. Phototherapy was discontinued after 1 day, and the infant was discharged without an exchange or top-up transfusion.

CONCLUSIONS

Maternal ABO-mismatched blood is an alternate source for IUT in instances when antigen-compatible allogenic blood is unavailable.

Frequency analysis of B lymphocytes specific for Rh antigens in naturally immunized Rh-negative women

BACKGROUND AND OBJECTIVES

Despite a successful outcome of the anti-D prophylaxis programme, alloimmunization still occurs. The aim of this study was to estimate the frequency of Rh-specific B lymphocytes in the peripheral blood of nine Rh-alloimmunized individuals at different time intervals after parturition.

MATERIALS AND METHODS

The donors' B lymphocytes were transformed with Epstein-Barr virus (EBV) and cultured at different cell densities over a feeder of human fetal fibroblasts. Culture supernatants were screened for human immunoglobulin by enzyme-linked immunosorbent assay (ELISA) and for anti-Rh antibody by using a direct haemagglutination technique. The percentage of CD19+ B lymphocytes in peripheral blood was determined by flow cytometry, and the frequency of Rh-specific B lymphocytes was estimated by limiting-dilution assay (LDA).

RESULTS

The frequency of Rh-specific B lymphocytes varied from 1 : 150 to 1 : 27,850 in different donors. There was a decrease in this frequency and level of anti-Rh antibody with increase in time interval between bleeding and last exposure to the antigen. Furthermore, a positive correlation was observed between the titre of Rh-specific antibody and frequency of Rh-specific B cells in each of three subjects bled at multiple time-points postdelivery.

CONCLUSIONS

The magnitude of the specific antibody response to Rh antigens varies greatly in Rh-alloimmunized women, which partly reflects the difference in frequency of specific B cells in these individuals.

[Transvaginal bleeding in pregnancy, as risk factor of Rhesus-D antigen isoimmunization]

OBJECTIVE

The aim of the present study was to evaluate transvaginal bleeding (TVB) as a risk factor for Rhesus isoimmunization during pregnancy, in order to optimize the application of Anti-D gammaglobulin in non-immunized pregnant women, as an alternative to the routine application of Anti-D at 28 weeks of gestation.

MATERIAL AND METHODS

This case-control study was conducted from 1995 to 2001 at Mexico's National Perinatology Institute. Cases (n = 24) were non-immunized pregnant women who showed positive anti-D antibody seroconversion during pregnancy or during the early puerperium. Controls (n = 24) were non-immunized pregnant women who enrolled after each case, with similar clinical characteristics but who had no anti-D antibody seroconversion during pregnancy. In all cases the newborns were Rh-positive. None of the patients received immunoprophylaxis at 28 weeks of gestation. The presence of TVB was recorded at any stage of pregnancy and before labor. Odds ratios with 95% confidence intervals were used to assess associations.

RESULTS

TVB was observed in 18/24 (75%) cases and in 5/24 (20%) controls. Preterm uterine contractions and threatened miscarriage were the most frequent causes of TVB. The presence of one TVB event during pregnancy increased 11.4 times (95% CI 2.9-44.0) the likelihood of Rhesus isoimmunization. TVB after 20 weeks of gestation increased the likelihood 5.0 times (95% CI 1.3-19.1). TVB before 20 weeks of gestation was not significantly associated with Rh isoimmunization (OR = 7.6, 95% CI 0.8-69.5).

CONCLUSIONS

Prophylaxis with anti-D gammaglobulin should be given to all non-immunized Rhesus-negative pregnant woman with TVB at any stage of pregnancy. The English version of this paper is available at:http://www.insp.mx/salud/index.html.

Longitudinal measurement of peak systolic velocity in the fetal middle cerebral artery for monitoring pregnancies complicated by red cell alloimmunisation: a prospective multicentre trial with intention-to-treat

OBJECTIVE

To evaluate the utilisation measurements of peak systolic velocities in the middle cerebral artery combined with B-mode ultrasound imaging to predict anaemia in an unselected population of pregnancies complicated by alloimmune antibodies known to cause immunological hydrops.

DESIGN

Prospective study on an intention-to-treat basis.

SETTING

Multicentre study in five large tertiary referral centres.

POPULATION

One hundred twenty-five fetuses with maternal alloantibodies known to cause immunological hydrops.

METHODS

If peak systolic velocity and B-mode scan were reassuring the pregnancy was monitored at 7-14 days interval. If either method showed signs of anaemia, an umbilical fetal blood sampling was performed. When the gestational age was greater than 35 weeks, labour was induced.

MAIN OUTCOME MEASURE

Moderate to severe anaemia at delivery.

RESULTS

Overall sensitivity to detect moderate to severe anaemia below 35 weeks (haemoglobin level below 0.65 multiples of median) was 88%. Specificity was 87%; positive predictive value was 53% and negative predictive value was 98%. The diagnosis of severe anaemia was missed in one fetus; however, the final outcome was good. The method was not useful after 35 weeks.

CONCLUSIONS

Middle cerebral artery peak systolic velocity is a highly sensitive non-invasive means for determining the degree of anaemia present in red blood cell alloimmunised pregnancies. The widespread use of the Doppler method will minimise fetal complications associated with amniocentesis and fetal blood sampling. Non-invasive measurement of middle cerebral artery peak systolic velocities is more convenient and acceptable to alloimmunised pregnancies and may significantly lower health care costs. A Doppler interval of seven days is recommended.

Isoimmunization is unlikely to be the cause of hemolysis in ABO-incompatible but direct antiglobulin test-negative neonates

OBJECTIVE

It is stated that the direct antiglobulin (Coombs') test (DAT) may be negative in ABO hemolytic disease of the newborn. Thus, significant jaundice in neonates who are A-B incompatible with their mothers but DAT test negative is often attributed to isoimmunization and another diagnosis is not sought. We wished to determine the rate of bilirubin production, as an objective measure of hemolysis, in 2 groups of DAT-negative neonates--ABO-compatible and ABO-incompatible--and in DAT-positive ABO-incompatible neonates.

METHODS

In consecutive, term, healthy newborns who were admitted to the general care nursery, we measured the level in parts per million (ppm) of end-tidal breath carbon monoxide (CO), corrected for inspired CO (ETCOc), an index of the rate of bilirubin production. We compared the levels in DAT-negative ABO-incompatible neonates with those in ABO-compatible neonates and with the levels in DAT-positive ABO-incompatible neonates. Statistical analysis was performed using 2-sample t and chi(2) tests.

RESULTS

There was no significant difference between the mean 12-hour ETCOc levels in DAT-negative ABO-incompatible neonates (n = 60, 2.2 +/- 0.6 ppm) versus DAT-negative ABO-compatible neonates (n = 171, 2.1 +/- 0.6 ppm), although there was a difference between the mean levels in DAT-positive ABO-incompatible neonates (n = 14, 3.4 +/- 1.8 ppm) and the DAT-negative groups. Four DAT-negative ABO-incompatible neonates had elevated ETCOc levels; in 2, we diagnosed a specific hematologic abnormality, namely, glucose-6-phosphate dehydrogenase deficiency in 1 and elliptocytosis in the other.

CONCLUSION

In DAT-negative newborns with significant jaundice or increased bilirubin production, even if ABO-incompatible, a cause other than isoimmunization should be sought.

Amniotic fluid delta OD 450 values accurately predict severe fetal anemia in D-alloimmunization

OBJECTIVE

To assess the diagnostic accuracy of amniotic fluid Delta OD 450 values in the second and third trimesters of D-alloimmunized pregnancies.

METHODS

We searched our database for singleton D-alloimmunized pregnancies with nonhydropic fetuses, where amniocentesis was performed within 4 days of first fetal blood sampling. Amniotic fluid Delta OD 450 values were plotted on an extrapolated Liley's chart. Sensitivity and specificity were calculated for two commonly used cutoff levels, Liley's zone 3 and the upper third of Liley's zone 2. Severe fetal anemia was defined as a hemoglobin concentration of more than 5 standard deviations below the normal mean for corresponding gestational age.

RESULTS

Seventy-nine pregnancies met our inclusion criteria. Overall accuracy of the extrapolated Liley's curve in predicting severe fetal anemia was 75% (95% confidence interval [CI] 64, 84) for zone 3 and 86% (95% CI 77, 93) when the upper third of zone 2 was included. Sensitivity of Delta OD 450 values in Liley's zone 3 or the upper third of Liley's zone 2 was 95% (95% CI 74, 100) before and 98% (95% CI 89, 100) after 27 weeks.

CONCLUSION

Liley's extrapolated curve predicts severe fetal anemia with reasonable accuracy and high sensitivity.

Role of HLA antigens in Rh (D) alloimmunized pregnant women from Mumbai, Maharashtra, India

Immunogenetic studies in various diseases provide potential genetic markers. We have studied the incidence of HLA A, B, C, DR and DQ loci antigen in Rh (D) antigen isoimmunized mothers compared to those nonimmunized isoimmunized Rh negative mothers. Seventy six mothers who were immunized to Rh (D) antigen due to pregnancy (responders) and fifty four mothers who did not develop Rh (D) isoimmunization despite positive pregnancies (nonresponders) were selected for the study. Standard methods of serological HLA typing, ABO and Rh (D) groups, and screening for Rh D antibodies were used. 392 unrelated individuals from the population were compared as controls. In addition 45 unrelated individuals from the same population were typed for HLA DRB and DQB gene using PCR-SSP kits. The genotype frequencies of HLA A2, A3, A28, B13, B17, B35, B52, B60, Cw2, Cw6, DR4, and DQ3 were significantly increased, while the frequencies of the HLA A11, A29, A31, B7, B37, B51, Cw1 and DR9 were decreased in the responder women when compared to the non-responder women. HLA A30 (19) split antigen was not identified in immunized women while HLA A23 (9) split antigen was not identified in non immunized women. HLA A3, B17, Cw2 and DR4 showed a significant relative risk among the immunized responder women. When compared with Rh immunized women (responders) reported from USA, England and Hungary the phenotype frequencies of HLA A11, A24, A28, B5, B17, B40, DR2 and DR5 were increased while HLA A23, B8, B18, and DR6 were decreased in the Indian Rh immunized women. Two locus haplotype frequency analysis observed among the responders women revealed that among the significant haplotypes expressed A2-B5, B7-Cw1, DR2-DQ1 were highly significant haplotypes in positive linkage, while A1-B5, and A1-B7 were in significant negative linkage disequilibrium. The haplotype frequencies were <or= one when these common hapoltypes were compared with control population. Thus in the present study it is evident that the inheritance of HLA A3, B17, Cw2 and DR4 increases the relative risk factor by 2.6 times among Indian Rh isoimmunized women. Further, it is evident that there are significant differences in the observed HLA antigen frequencies and two locus haplotypes in Rh isoimmunized women when compared to women from USA, UK and Hungary due to extreme HLA polymorphism in different populations of the world.

Quantification of foetomaternal haemorrhage. An analysis of two cytometric techniques and a semiquantitative gel agglutination test

Traditional tests to screen for foetomaternal haemorrhage are time-consuming and difficult to perform. The Kleihauer test is widely used but difficult to standardize. We evaluated three techniques for quantifying foetomaternal haemorrhage: a semiquantitative gel agglutination test and two flow cytometric techniques. The gel agglutination test is based on the consumption of anti-D reagent by D+ cells, analysing the reaction of the supernatant against indicator cells in a Coombs-gel card. In the two colour direct immunofluorescent technique, the sample is incubated with Per-CP labelled anti CD45 antibody, fixed with glutaraldehyde and permeabilized by exposure to Triton X-100. An aliquot is stained with an antibody to foetal haemoglobin, conjugated with fluorescein isothiocyanate or phycoerythrin. The indirect immunofluorescent technique is based on the labelling of Rh (D) antigen with an anti D reagent, followed by the addition of an anti IgG antibody conjugated with phycoerythrin. Foetomaternal haemorrhage was not detected in 75 of the 85 samples analysed by the direct immunofluorescent technique. In the remaining 10 samples, the volume was very low. Thirty-five samples with Rh (D) antigen incompatibility were analysed in parallel by the indirect immunofluorescent technique and in 15 of the 35 samples, the gel agglutination technique was also carried out. The three techniques gave similar results. The gel agglutination test can be used to screen for foetomaternal haemorrhage, while greater volumes should be quantified by flow cytometric techniques.