Estimating the cost of Rh testing and prophylaxis in early pregnancy: A time-driven activity-based costing study.

OBJECTIVE: To estimate the cost of Rhesus (Rh) testing and prophylaxis for first-trimester vaginal bleeding in the ambulatory setting. STUDY DESIGN: We used time-driven, activity-based costing to analyze tasks associated with Rh testing and prophylaxis of first-trimester vaginal bleeding at one hospital-based outpatient and two independent reproductive health clinics. At each site, we observed 10 patients undergoing Rh-typing and two patients undergoing Rh prophylaxis. We computed the costs of blood Rh-typing by both fingerstick and phlebotomy, cost of locating previous blood type in the electronic health record (available for 69.8% of hospital-based patients), and costs associated with Rh immune globulin prophylaxis. All costs are reported in 2021 US dollars. RESULTS: The hospital-based clinic reviewed the electronic health record to confirm Rh-status (cost, $26.18 per patient) and performed a phlebotomy, at $47.11 per patient, if none was recorded. The independent clinics typed blood by fingerstick, at a per-patient cost of $4.07. Rh-immune globulin administration costs, including the medication, were similar across facilities, at a mean of $145.66 per patient. Projected yearly costs for testing and prophylaxis were $55,831 for the hospital-based clinic, which was the lowest-volume site, $47,941 for Clinic A, which saw 150 patients/month, and $185,654 for Clinic B, which saw 600 patients/month. CONCLUSIONS: Rh testing and prophylaxis for first-trimester vaginal bleeding generates considerable costs for outpatient facilities, even for Rh-positive patients with a prior blood type on record. IMPLICATIONS: Rh testing and prophylaxis for first-trimester bleeding generate considerable costs even for Rh-positive patients and those with a previously known blood type. These findings highlight the need to reconsider this practice, which is no longer supported by evidence and already safely waived in multiple medical settings in the United States and around the world.

Guideline No. 448: Prevention of Rh D Alloimmunization.

OBJECTIVE: This guideline provides recommendations for the prevention of Rh D alloimmunization (isoimmunization) in pregnancy, including parental testing, routine postpartum and antepartum prophylaxis, and other clinical indications for prophylaxis. Prevention of red cell alloimmunization in pregnancy with atypical antigens (other than the D antigen), for which immunoprophylaxis is not currently available, is not addressed in this guideline. TARGET POPULATION: All Rh D-negative pregnant individuals at risk for Rh D alloimmunization due to potential exposure to a paternally derived fetal Rh D antigen. OUTCOMES: Routine postpartum and antepartum Rh D immunoprophylaxis reduces the risk of Rh D alloimmunization at 6 months postpartum and in a subsequent pregnancy. BENEFITS, HARMS, AND COSTS: This guideline details the population of pregnant individuals who may benefit from Rho(D) immune globulin (RhIG) immunoprophylaxis. Thus, those for whom the intervention is not required may avoid adverse effects, while those who are at risk of alloimmunization may mitigate this risk for themselves and/or their fetus. EVIDENCE: For recommendations regarding use of RhIG, Medline and Medline in Process via Ovid and Embase Classic + Embase via Ovid were searched using both the trials and observational studies search strategies with study design filters. For trials, the Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects via Ovid were also searched. All databases were searched from January 2000 to November 26, 2019. Studies published before 2000 were captured from the grey literature of national obstetrics and gynaecology specialty societies, luminary specialty journals, and bibliographic searching. A formal process for the systematic review was undertaken for this update, as described in the systematic review manuscript published separately. VALIDATION METHODS: The authors rated the quality of evidence and strength of recommendations using the SOGC's modified GRADE approach. See Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional [weak] recommendations). INTENDED AUDIENCE: The intended users of this guideline include prenatal care providers such as obstetricians, midwives, family physicians, emergency room physicians, and residents, as well as registered nurses and nurse practitioners. TWEETABLE ABSTRACT: An updated Canadian guideline for prevention of Rh D alloimmunization addresses D variants, cffDNA for fetal Rh type, and updates recommendations on timing of RhIG administration. SUMMARY STATEMENTS: RECOMMENDATIONS.

[Prevention of Rh D alloimmunization in the first trimester of the pregnancy: French College of Obstetricians and Gynecologists guidelines for clinical practice]. / Prévention de l'allo-immunisation anti-RH1 au premier trimestre de la grossesse : recommandations pour la pratique clinique du Collège national des gynécologues-obstétriciens français.

OBJECTIVE: To provide recommendations for the prevention of Rh D alloimmunization in the first trimester of pregnancy. MATERIALS AND METHODS: The quality of evidence of the literature was assessed following the GRADE methodology with questions formulated in the PICO format (Patients, Intervention, Comparison, Outcome) and outcomes defined a priori and classified according to their importance. An extensive bibliographic search was performed on Pubmed, Cochrane, EMBASE, and Google Scholar databases. The quality of evidence was assessed (high, moderate, low, very low) and a recommendation was formulated: (i) strong, (ii) weak, or (iii) no recommendation. The recommendations were reviewed in two rounds with reviewers from the scientific board of the French College of the OB/GYN (Delphi survey) to select the consensus recommendations. RESULTS: The three recommendations from PICO questions reached agreement using the Delphi method. It is recommended not to administer Rh D immunoglobulin before 12 weeks of gestation to reduce the risk of alloimmunization in case of abortion or miscarriage, in RhD negative patients when the genitor is RhD positive or unknown (Weak recommendation. Very low-quality evidence). It is recommended not to administer Rh D immunoglobulin before 12 weeks of gestation to reduce the risk of alloimmunization in cases of bleeding in an ongoing intrauterine pregnancy (Weak recommendation. Very low-quality evidence). The literature data are insufficient in quality and quantity to determine if the injection of Rh D immunoglobulin reduces the risk of alloimmunization in the case of an ectopic pregnancy (No recommendation. Very low-quality evidence). CONCLUSION: Even though the quality of evidence from the studies is very low, it is recommended not to administer Rh D immunoglobulin in case of abortion, miscarriage or bleeding before 12 weeks of amenorrhea. The quality of evidence was too low to issue a recommendation regarding ectopic pregnancy.

Time points and risk factors for RhD immunizations after the implementation of targeted routine antenatal anti-D prophylaxis: A retrospective nationwide cohort study.

INTRODUCTION: Targeted routine antenatal anti-D prophylaxis was introduced to the national prophylaxis program in Finland in late 2013. The aim of this study was to assess the incidence, time-points, and risk factors for Rhesus D immunization after the implementation of routine antenatal anti-D prophylaxis, in all women in Finland with antenatal anti-D antibodies detected in 2014-2017. MATERIAL AND METHODS: In a nationwide population-based retrospective cohort study, the incidence, time-points, and risk factors of anti-D immunizations were analyzed. Information on antenatal screening was obtained from the Finnish Red Cross Blood Service database, and obstetric data from hospital records and the Finnish Medical Birth Register. RESULTS: The study included a total of 228 women (197 with complete data for all pregnancies). After the implementation of routine antenatal anti-D prophylaxis, the prevalence of pregnancies with anti-D antibodies decreased from 1.52% in 2014 to 0.88% in 2017, and the corresponding incidence of new immunizations decreased from 0.33% to 0.10%. Time-points for detection of new anti-D antibodies before and after 2014 were the first screening sample at 8-12 weeks of gestation in 52% vs 19%, the second sample at 24-26 weeks in 20% vs 50%, and the third screening at 36 weeks in 28% vs 32%. CONCLUSIONS: The incidence of new anti-D immunizations decreased as expected after the implementation of routine antenatal anti-D prophylaxis. True failures are rare and they mainly occur when the prophylaxis is not given appropriately, suggesting a need for constant education of healthcare professionals on the subject.

Clinical value of different anti-D immunoglobulin strategies for preventing Rh hemolytic disease of the fetus and newborn: A network meta-analysis.

BACKGROUND: Several anti-D immunoglobulin strategies exist for preventing Rh hemolytic disease of the fetus and newborn. This study systematically assessed the clinical value of those therapeutic strategies. METHODS: The Web of Science, PubMed, EMBASE, China National Knowledge Infrastructure (CNKI) and Wanfang databases were searched for eligible studies that evaluated the value of different anti-D immunoglobulin strategies in preventing maternal anti-D antibody sensitization. Combined odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated. The network meta-analysis was conducted using Stata 14.2 and WinBUGS 1.4.3 software. RESULTS: Twenty-four original studies involving 64860 patients were included. Among all therapeutic measures, injecting 300 µg anti-D immunoglobulin at 28 and 34 gestational weeks (antenatal 5/E) appeared to be the most effective measure for preventing maternal antibody sensitization (surface under the cumulative ranking curve [SUCRA] = 96.8%), while a single injection at 28 gestational weeks (SUCRA = 89.2%) was the second most effective. Administering no injection or a placebo (SUCRA = 0.0%) was the least effective intervention measure. CONCLUSION: Among the therapeutic measures, antenatal 5/E appeared to be the best method for reducing the positive incidence of anti-D antibodies in the maternal serum; thus, it may be the most effective treatment for preventing fetal hemolytic disease.

Rhesus D factor (RhD) negative women's experiences with pregnancy: An interpretive description.

BACKGROUND: The development of rh immune globulin (RhIG) for the prevention of Rhesus D (RhD) alloimmunization has significantly decreased the incidence of RhD alloimmunization. Despite long-standing prevention, the experiences of RhD negative women with pregnancy is absent in the literature. AIM: The purpose of this study was to explore the experiences of RhD negative women with pregnancy. METHODS: Utilizing an Interpretive Description approach, semi-structured interviews were conducted with RhD negative women about their pregnancies. This study took place within the geographic context of northern British Columbia (BC). The analysis involved a two-cycle approach to identify themes within the data. FINDINGS: Sixteen RhD negative women that live in northern BC participated in this study. The analysis identified that RhD negative women are uninformed and want to be involved in the decision-making process regarding the prevention of RhD alloimmunization. The themes that emerged from the interview data were communication, information-seeking behaviour, out of sight out of mind, choice and trust, and patient advocacy. DISCUSSION: The participants in this study described lacking information regarding the prevention of RhD alloimmunization. They sought information to overcome the gaps in knowledge and a desire to be involved in the decision-making process. CONCLUSION: RhD negative women want information and to be involved in the decision-making process in the prevention of RhD alloimmunization. Working with RhD negative women to develop decision-aids and/or other educational tools to aid in the decision-making process are warranted.

Very Prolonged Anti-D: Confusion Surrounding Alloimmunization After Extra Rh Immunoglobulin: A Case Report.

BACKGROUND: Rh immunoglobulin (RhIg) is usually detectable a maximum of 12 to 14 weeks after administration. Positive antibodies beyond this time frame suggests alloimmunization. CASE: A woman had three pregnancies over a 6-month period, with two first-trimester losses. She received RhIg in the first pregnancy but not in the second. Two months after the second loss, in her third pregnancy, she received RhIg at week 6 due to first-trimester bleeding. She was subsequently anti-D antibody positive up to week 28 with antibodies too low to titre, leading to confusion about whether alloimmunization had occurred. CONCLUSION: Rh Ig administration led to positive anti-D antibodies lasting 22 weeks, suggesting keeping this differential diagnosis in mind when suspecting alloimmunization with positive antibodies at levels too low to titre.

Severe haemolytic disease of a newborn with variant D mimicking blocked-D phenomenon.

Anti-D is still the most common antibody causing severe haemolytic disease of the fetus and newborn (HDFN). In a mother with a very high titer of anti-D, antibodies can coat and block the D antigens on the red blood cells of the newborn. This blocking phenomenon prevents agglutination of the D-positive red cells with the IgM anti-D typing reagent, giving false negative results. Here, we report the case of a newborn with variant D phenotype and severe HDFN, which mimicked the blocked-D phenomenon, which, at the first instance, confused both the treating clinicians and the transfusion service personnel.

Single dose v two-dose antenatal anti-D prophylaxis: a randomised controlled trial.

OBJECTIVE: To compare rates of detectability of circulating Rh(D)-immunoglobulin (anti-D) at delivery with single and two-dose antenatal anti-D prophylaxis (RAADP) regimens; to compare compliance with the two regimens. DESIGN: Open label, randomised controlled trial between May 2013 and November 2015. SETTING, PARTICIPANTS: 277 women who attended a tertiary obstetric referral hospital in Perth for antenatal care and were at least 18 years of age, less than 30 weeks pregnant and yet to receive RAADP, Rh(D)-negative (negative antibody screen), and who intended to deliver their baby at the hospital. Exclusion criteria were prior anti-D sensitisation, any contraindication of anti-D administration, and a history of isolated IgA deficiency. INTERVENTIONS: One 1500 IU anti-D dose at 28 weeks of pregnancy (single dose regimen); two doses of 625 IU each at 28 and 34 weeks of pregnancy (two-dose regimen). MAIN OUTCOME MEASURES: The primary outcome was the proportion of women with detectable anti-D levels at delivery; the secondary outcome was compliance with the allocated RAADP regimen. RESULTS: Circulating anti-D was detectable at delivery in a greater proportion of women in the two-dose group (111 of 129, 86%) than in the single dose group (70 of 125, 56%; P < 0.001). Compliance was not significantly different between the single dose (86 of 138, 61%) and two-dose groups (70 of 139, 50%; P = 0.06). CONCLUSIONS: The two-dose RAADP schedule currently recommended in Australia provides better protection against Rh(D) sensitisation than a one-dose regimen. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry (ACTRN12613000661774).

Association of a positive direct antiglobulin test with chronic immune thrombocytopenia and use of second line therapies in children: A multi-institutional review.

Immune thrombocytopenia (ITP) is the most common autoimmune cytopenia in children. Approximately, 25% of patients develop chronic disease, which may be unpredictable and challenging to treat. It is not currently possible to predict at the time of presentation which patients will have chronic disease or will experience symptoms requiring second-line therapy defined as treatment beyond corticosteroids, intravenous immunoglobulin, or Rh immune globulin. A multi-institutional retrospective review of 311 pediatric patients with ITP was performed with the goal of identifying clinical characteristics associated with disease course. In a cohort of 216 patients tested and for whom disease status was known, a positive direct antiglobulin test (DAT) was associated with chronic ITP vs spontaneous resolution of disease (29.2% vs 8.1%, P < 0.001) as well as the need for treatment with second line agents (38.5% vs 11.4%, P < 0.001) in 241 patients. Controlling for the effect of Evans syndrome, defined as having two immune cytopenias, a positive DAT was independently associated with chronic ITP (OR = 2.7, 95% CI: 1.0-7.2, P = 0.041) and use of second-line agents (OR: 3.6, 95% CI: 1.7-7.7, P = 0.001) by multivariate logistic regression model. These findings demonstrate an association with positive DAT and chronic disease, as well as refractory disease requiring second-line agents.

Relevance and costs of RHD genotyping in women with a weak D phenotype.

OBJECTIVES: For pregnant women, the serologic test results of D antigen will determine the frequency of RBC antibody detection as well as the indication for RhIG prophylaxis. RHD genotyping is the only method that may provide clear guidance on prophylaxis for women with a weak D phenotype. This analysis evaluated the economical implications of using RHD genotyping to guide RhIG prophylaxis among pregnant women with a serological weak D phenotype. METHODS: We compared the costs of 2 strategies in a cohort of 273 women with weak D phenotype. In the first strategy, we did not perform genotyping and all women with weak D phenotypes were treated as if they were D-, thus considered to be a risk of RhD alloimmunization. These women all received the prophylactic follow up. In the second strategy, RHD genotyping was performed on all women with a serologic weak D phenotype. Then, the follow-up will be determined by phenotype deduced from genotype. RESULTS: On the studied cohort, the additional expense occurred by genotyping is 26,536 €. RHD Genotyping has highlighted 162 weak D Type 1, 2 3, that could safely be managed as D+ and 111 partial D to consider as D-. By comparing the 2 strategies, the savings generated by genotyping the patients of our cohort are € 12,046 for the follow up of one pregnancy. Knowing that in France, a woman has on average 2 pregnancies and that the genotyping is carried out only once, the savings generated for the following pregnancies would be € 38,581. CONCLUSIONS: Performing RHD genotyping for pregnant women with a weak D phenotype enables to clearly identify weak D type 1, 2 or 3 from the other variants at risk of alloimmunization. This analysis generates savings in terms of follow-up schedule of pregnant women and RhIG prophylaxis. It also allows saving of D- products for patient with a weak D type 1, 2 or 3 in case of a transfusion need.

Prospective quantification of fetomaternal hemorrhage with dilation and evacuation procedures.

OBJECTIVE: To describe fetomaternal hemorrhage (FMH) during second-trimester dilation and evacuation (D&E) to evaluate if Rhesus-immune globulin (RhIG) 100 mcg (used in the United Kingdom) and 300 mcg (used in the United States) provide adequate prophylaxis. STUDY DESIGN: We conducted an exploratory prospective descriptive study of women undergoing D&E between 15 weeks 0 days and 23 weeks 6 days of gestation. Enrolled participants had Kleihauer-Betke testing on specimens obtained before and after D&E. We assessed the main outcome measures of FMH in mL suggesting need for more than 100 mcg and 300 mcg RhIG (FMH of 10 mL and 30 mL fetal whole blood, respectively) and association of postprocedure FMH with demographic characteristics and procedure-related variables. RESULTS: The 300 participants had a mean gestational age of 19 weeks 6 days±2 weeks 2 days. The median preprocedure FMH was 0 mL (range 0-50 mL) with 2 (0.67%) women exceeding 10 mL (19 mL and 50 mL). The median postprocedure FMH was 1 mL (range 0-60 mL). Almost all participants had postprocedure FMH <10 mL (n=295, 98.3%) and <30 mL (n=298, 99.3%). All participants under 18 weeks had FMH <10 mL. We found no demographic or procedure-related factors to be predictive of FMH quantity. CONCLUSIONS: FMH occurring with routine second-trimester D&E procedures is minimal. Adequate prophylaxis with RhIG 100 mcg and 300 mcg occurred in >98% of women and in all cases <18 weeks of gestation. This study is the first step to potentially reducing the dose and costs of RhIG administration with D&E. IMPLICATIONS: This study is a first step in quantifying fetomaternal hemorrhage with routine dilation and evacuation procedures; larger trials are needed, especially to understand why some women have recognizable hemorrhage preprocedure. If dosing requirements are too high with current guidelines, lower doses will result in resource and cost savings.

Usefulness of maternal fetal red blood cell count in rhesus-positive pregnant women.

Background Fetal red blood cells (FRBC) in maternal blood are counted in rhesus-negative women to determine the amount of anti-D immunoglobulin to be administered in the case of a rhesus-positive fetus. In rhesus-positive pregnant women this is done in not always very well-defined indications including trauma, miscarriage, fetal death and diminished fetal movements. The aim of this study is to determine if the detection of FRBC is useful in rhesus-positive pregnant woman. This was done by assessing maternal and fetal characteristics that are more likely to give a positive test. Materials and methods This was a retrospective cohort study. Results A total of 169 FRBC tests were performed in 161 rhesus-positive pregnant women. FRBC were found in 45 (26.6%) of the women. Three patients experienced a miscarriage although their FRBC tests were negative (p = 0.295). Of the seven patients who experienced unexpected stillbirths, three tested positive. The deaths were not less likely to occur if the results had been negative (p = 0.631). There was a statistically significant difference between the different types of trauma indications (p = 0.025): the test was more likely positive if there had been a fall on the ground or staircase or blunt trauma (p = 0.041, 0.026 and 0.018, respectively). FRBC were not more frequently present in the absence of fetal movements (n = 16, p = 0.693). Conclusion FRBC in maternal blood were more likely positive in the case of a fall on the ground, or from a staircase. However, a positive test does not necessarily imply fetal pathology and, therefore, does not contribute to clinical management.

High-throughput non-invasive prenatal testing for fetal rhesus D status in RhD-negative women not known to be sensitised to the RhD antigen: a systematic review and economic evaluation.

BACKGROUND: High-throughput non-invasive prenatal testing (NIPT) for fetal rhesus (D antigen) (RhD) status could avoid unnecessary treatment with routine anti-D immunoglobulin for RhD-negative women carrying a RhD-negative fetus, although this may lead to an increased risk of RhD sensitisations. OBJECTIVES: To systematically review the evidence on the diagnostic accuracy, clinical effectiveness and implementation of high-throughput NIPT and to develop a cost-effectiveness model. METHODS: We searched MEDLINE and other databases, from inception to February 2016, for studies of high-throughput NIPT free-cell fetal deoxyribonucleic acid (DNA) tests of maternal plasma to determine fetal RhD status in RhD-negative pregnant women who were not known to be sensitised to the RhD antigen. Study quality was assessed with the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) and A Cochrane Risk of Bias Assessment Tool: for Non-Randomised Studies of Interventions (ACROBAT-NRSI). Summary estimates of false-positive rates (FPRs) and false-negative rates (FNRs) were calculated using bivariate models. Clinical effectiveness evidence was used to conduct a simulation study. We developed a de novo probabilistic decision tree-based cohort model that considered four alternative ways in which the results of NIPT could guide the use of anti-D immunoglobulin antenatally and post partum. Sensitivity analyses (SAs) were conducted to address key uncertainties and model assumptions. RESULTS: Eight studies were included in the diagnostic accuracy review, seven studies were included in the clinical effectiveness review and 12 studies were included in the review of implementation. Meta-analyses included women mostly at or post 11 weeks' gestation. The pooled FNR (women at risk of sensitisation) was 0.34% [95% confidence interval (CI) 0.15% to 0.76%] and the pooled FPR (women needlessly receiving anti-D) was 3.86% (95% CI 2.54% to 5.82%). SAs did not materially alter the overall results. Data on clinical outcomes, including sensitisation rates, were limited. Our simulation suggests that NIPT could substantially reduce unnecessary use of antenatal anti-D with only a small increase in the risk of sensitisation. All large implementation studies suggested that large-scale implementation of high-throughput NIPT was feasible. Seven cost-effectiveness studies were included in the review, which found that the potential for the use of NIPT to produce cost savings was dependent on the cost of the test. Our de novo model suggested that high-throughput NIPT is likely to be cost saving compared with the current practice of providing routine antenatal anti-D prophylaxis to all women who are RhD negative. The extent of the cost saving appeared to be sufficient to outweigh the small increase in sensitisations. However, the magnitude of the cost saving is highly sensitive to the cost of NIPT itself. LIMITATIONS: There was very limited evidence relating to the clinical effectiveness of high-throughput NIPT, with no evidence on potential adverse effects. The generalisability of the findings to non-white women and multiple pregnancies is unclear. CONCLUSIONS: High-throughput NIPT is sufficiently accurate to detect fetal RhD status in RhD-negative women from 11 weeks' gestation and would considerably reduce unnecessary treatment with routine anti-D immunoglobulin, potentially resulting in cost savings of between £485,000 and £671,000 per 100,000 pregnancies if the cost of implementing NIPT is in line with that reflected in this evaluation. FUTURE WORK: Further research on the diagnostic accuracy of NIPT in non-white women is needed. STUDY REGISTRATION: This study is registered as PROSPERO CRD42015029497. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

No. 133-Prevention of Rh Alloimmunization.

OBJECTIVE: To provide guidelines on use of anti-D prophylaxis to optimize prevention of rhesus (Rh) alloimmunization in Canadian women. OUTCOMES: Decreased incidence of Rh alloimmunization and minimized practice variation with regards to immunoprophylaxis strategies. EVIDENCE: The Cochrane Library and MEDLINE were searched for English-language articles from 1968 to 200 I, relating to the prevention of Rh alloimmunization. Search terms included: Rho(D) immune globulin, Rh iso- or aile-immunization, anti-D, anti-Rh, WinRho, Rhogam, and pregnancy. Additional publications were identified from the bibliographies of these articles. All study types were reviewed. Randomized controlled trials were considered evidence of highest quality, followed by cohort studies. Key individual studies on which the principal recommendations are based are referenced. Supporting data for each recommendation is briefly summarized with evaluative comments and referenced. VALUES: The evidence collected was reviewed by the Maternal-Fetal Medicine and Genetics Committees of The Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the Evaluation of Evidence guidelines developed by the Canadian Task Force on the Periodic Health Exam. RECOMMENDATIONS: VALIDATION: These guidelines have been reviewed by the MaternalFetal Medicine Committee and the Genetics Committee, with input from the Rh Program of Nova Scotia. Final approval has been given by the Executive and Council of The Society of Obstetricians and Gynaecologists of Canada. SPONSORS: The Society of Obstetricians and Gynaecologists of Canada.

A Guide to Terminology for Rh Immunoprophylaxis.

Rh immunoprophylaxis for Rh-negative women requires an understanding of terminology used for Rh blood typing laboratory reports. The pathophysiology of Rh hemolytic disease of the fetus and newborn was elucidated by studies in rhesus monkeys. Subsequent studies revealed that the human blood group antigen responsible for Rh hemolytic disease of the newborn (D antigen) is related to, but different from, the rhesus monkey antigen. Weak expression of the D antigen on red cells, originally termed D, is currently reported by laboratories as a "serologic weak D phenotype," which can be further defined by RHD genotyping to be either a weak D type or a partial D phenotype. Weak D types 1, 2, or 3 are molecularly defined RHD weak D types, which have an adequate number of intact D antigens to be managed safely as Rh-positive. Partial D phenotypes result from mutations causing loss of one or more D epitopes. Most persons with a partial D phenotype have sufficient D antigen to type as Rh-positive. Some women with a partial D phenotype are detected as serologic weak D phenotypes by routine Rh typing. Whether they type as Rh-positive or serologic weak D phenotype, after being exposed to Rh-positive red cells by transfusion or pregnancy, women with partial D phenotype can form anti-D antibodies and, if they do, are at risk for hemolytic disease of the fetus and newborn. A pregnant woman with a laboratory report of a serologic weak D phenotype should be further tested for her RHD genotype to resolve whether her case should be managed as Rh-positive or Rh-negative. For more than five decades, the practice of Rh immunoprophylaxis has remained unchanged in terms of the dose of Rh immune globulin and timing of injections. In contrast, advances in the science of Rh blood typing have resulted in a continuously evolving terminology, obliging obstetricians to update their vocabulary to guide their practice. The following review and glossary provide guidance for current Rh terminology and the rationale for changes.

Practice Bulletin No. 181 Summary: Prevention of Rh D Alloimmunization.

Advances in the prevention and treatment of Rh D alloimmunization have been one of the great success stories of modern obstetrics. There is wide variation in prevalence rates of Rh D-negative individuals between regions, for example from 5% in India to 15% in North America (1). However, high birth rates in low prevalence areas means Rh hemolytic disease of the newborn is still an important cause of morbidity and mortality in countries without prophylaxis programs (1). In such countries, 14% of affected fetuses are stillborn and one half of live born infants suffer neonatal death or brain injury (1). The routine use of Rh D immune globulin is responsible for the reduced rate of red cell alloimmunization in more economically developed countries. First introduced in the 1970s, the postpartum administration of Rh D immune globulin reduced the rate of alloimmunization in at-risk pregnancies from approximately 13-16% to approximately 0.5-1.8% (2, 3). The risk was further reduced to 0.14-0.2% with the addition of routine antepartum administration (2, 3). Despite considerable proof of efficacy, there are still a large number of cases of Rh D alloimmunization because of failure to follow established protocols. In addition, there are new data to help guide management, especially with regard to weak D phenotype women. The purpose of this document is to provide evidence-based guidance for the management of patients at risk of Rh D alloimmunization.

Practice Bulletin No. 181: Prevention of Rh D Alloimmunization.

Advances in the prevention and treatment of Rh D alloimmunization have been one of the great success stories of modern obstetrics. There is wide variation in prevalence rates of Rh D-negative individuals between regions, for example from 5% in India to 15% in North America (1). However, high birth rates in low prevalence areas means Rh hemolytic disease of the newborn is still an important cause of morbidity and mortality in countries without prophylaxis programs (1). In such countries, 14% of affected fetuses are stillborn and one half of live born infants suffer neonatal death or brain injury (1). The routine use of Rh D immune globulin is responsible for the reduced rate of red cell alloimmunization in more economically developed countries. First introduced in the 1970s, the postpartum administration of Rh D immune globulin reduced the rate of alloimmunization in at-risk pregnancies from approximately 13-16% to approximately 0.5-1.8% (2, 3). The risk was further reduced to 0.14-0.2% with the addition of routine antepartum administration (2, 3). Despite considerable proof of efficacy, there are still a large number of cases of Rh D alloimmunization because of failure to follow established protocols. In addition, there are new data to help guide management, especially with regard to weak D phenotype women. The purpose of this document is to provide evidence-based guidance for the management of patients at risk of Rh D alloimmunization.

Can serological methods help distinguish between prophylactic and alloimmune anti-D?

OBJECTIVES: Enzyme indirect antiglobulin test (EIAT) and polyethylene glycol IAT (PIAT) were evaluated for their potential use as tests to distinguish between prophylactic and alloimmune anti-D in plasma by comparing with a tube variation of the standard low ionic strength solution-IAT (LISS-IAT). BACKGROUND: Laboratories performing the screening of RhD-negative pregnant women are required to provide clinicians with guidance as to the source of detected RhD antibodies. Currently, this is derived from RhIg immunoprophylaxis history, agglutination scores and titration results, where performed. A serological test that can differentiate between prophylactic and alloimmune anti-D would be useful in the diagnosis of RhD alloimmunisation in pregnant women. MATERIALS AND METHODS: Plasma samples (n = 273) [fresh (collected from April 2014 to February 2015) and frozen (up to 2 years)] from antenatal females, preoperative males and females over child-bearing age were used in this study. Samples were identified as containing anti-D by routine column agglutination (CAT) and were tested by tube LISS-IAT, EIAT and PIAT, and a score difference was calculated. RESULTS: A total of 32% of alloimmune anti-D samples demonstrated an increase in agglutination score (+2 or +3) when tested by EIAT. A significant increase in agglutination score for alloimmune samples using EIAT compared with LISS-IAT was observed. EIAT had a sensitivity (Sn) of 59%, positive predictive value (PPV) of 100% and specificity (Sp) of 100% for alloimmune anti-D. CONCLUSION: EIAT is capable of confirming but not excluding the presence of alloimmune anti-D in samples where anti-D is detected in routine antibody screening.