Management and clinical consequences of red blood cell antibodies in pregnancy: A population-based cohort study

Comparison of conventional tube technique with automated gel microcolumn assay for antenatal antibody monitoring

BACKGROUND AND OBJECTIVES

Timely identification of pregnancies at risk of severe haemolytic disease of the fetus and newborn (HDFN) requires accurate and reproducible antibody titration. This study aimed to establish a critical titre for the gel microcolumn assay (GMA) corresponding to the critical titre of ≥16 for the conventional tube technique (CTT) and to evaluate GMA's suitability for routine antenatal antibody titration.

MATERIALS AND METHODS

Altogether, 147 antenatal plasma samples with clinically significant antibodies were studied, including eight pregnancies requiring intrauterine transfusions (IUTs). Twofold serial dilution titres with CTT were made in parallel with automated GMA. Single-dose red blood cells were used with a concentration of 3.5% for CTT and 0.8% for GMA. The critical titre for GMA was compared with CTT as the gold standard.

RESULTS

GMA titres were on average 2.88 (95% confidence interval [CI]: 2.72-3.05) dilutions higher than CTT titres. At a CTT titre of 16, the sensitivity and specificity of GMA titration were maximum (94%, 95% CI: 81-99 and 92%, 95% CI: 85-96, respectively) at a titre of 128, but one of the eight fetuses (12.5%) requiring IUTs would have been missed. At a GMA titre of ≥64, sensitivity and specificity were 100% (95% CI: 100-100) and 77% (95% CI: 68-84) respectively, but the number of pregnancies requiring clinical monitoring more than doubled (2.5×).

CONCLUSION

A GMA titre ≥64 could be considered a safe critical value for high-risk assessment. Despite being a fully automated method benefiting the screening laboratory, the additional workload and costs caused by unnecessary monitoring at delivery hospitals were unacceptable.

Clinical Performance of Cell-Free DNA for Fetal RhD Detection in RhD-Negative Pregnant Individuals in the United States

OBJECTIVE

To evaluate the performance of a cell-free DNA (cfDNA) assay that uses next-generation sequencing with quantitative counting templates for the clinical detection of the fetal RHD genotype in a diverse RhD-negative pregnant population in the United States.

METHODS

This retrospective cohort study was conducted in four U.S. health care centers. The same next-generation sequencing quantitative counting template cfDNA fetal RhD assay was offered to nonalloimmunized RhD-negative pregnant individuals as part of clinical care. Rh immune globulin (RhIG) was administered at the discretion of the clinician. The sensitivity, specificity, and accuracy of the assay were calculated considering the neonatal RhD serology results.

RESULTS

A total of 401 nonalloimmunized RhD-negative pregnant individuals who received clinical care in the period from August 2020 to November 2023 were included in the analysis. The D antigen cfDNA result was 100% concordant with the neonatal serology, resulting in 100% sensitivity, 100% positive predictive value (95% CI, 98.6-100% for both), 100% specificity, and 100% negative predictive value (95% CI, 97.4-100% for both). There were 10 pregnant individuals in whom the cfDNA analysis identified a non- RHD gene deletion, including RhDΨ (n=5) and RHD-CE-D hybrid variants (n=5). Rh immune globulin was administered antenatally to 93.1% of pregnant individuals, with cfDNA results indicating an RhD-positive fetus compared with 75.0% of pregnant individuals with cfDNA results indicating an RhD-negative fetus, signifying that clinicians were using the cfDNA results to guide pregnancy management.

CONCLUSION

This next-generation sequencing with quantitative counting templates cfDNA analysis for detecting fetal RhD status is highly accurate with no false-positive or false-negative results in 401 racially and ethnically diverse pregnant individuals with 100% follow-up of all live births. This study and prior studies of this assay support a recommendation to offer cfDNA screening for fetal Rh status as an alternative option to prophylactic RhIG for all nonalloimmunized RhD-negative individuals, which will result in more efficient and targeted prenatal care with administration of RhIG only when medically indicated.

The Utility of a Critical Antibody Titer in Anti-K Alloimmunized Pregnancies: A Systematic Review and Meta-Analysis of Diagnostic Test Accuracy

Anti-Kell (anti-K) alloimmunization is a known cause of severe hemolytic disease of the fetus and newborn (HDFN), yet the utility of a critical maternal antibody titer in guiding clinical management remains debated. We conducted a systematic review and meta-analysis to evaluate the diagnostic accuracy of a maternal anti-K titer threshold of ≥8 for predicting the need for intrauterine intervention due to severe anti-K-mediated HDFN. In parallel, we characterized all reported cases of severe HDFN occurring in the setting of low maternal anti-K titers (<8). Studies were excluded if they lacked reported titers, did not include K-positive or K-unknown fetuses, failed to report fetal outcomes, or included interventions that could lower maternal alloantibody levels. Studies that assessed all alloimmunized patients meeting inclusion criteria were incorporated into a diagnostic test accuracy (DTA) meta-analysis; all eligible studies were included in a qualitative synthesis. Fifty-four studies, comprising 582 fetuses, met inclusion criteria. Of these, 6 studies (350 fetuses) were included in the DTA analysis, which demonstrated a pooled sensitivity of 97.0% (95% CI, 88.7%-99.2%) and specificity of 33.1% (95% CI, 27.9%-38.8%) for an anti-K titer ≥8. Among fetuses affected by severe HDFN, 98.6% (204/207) were associated with maternal anti-K titers ≥8. These findings suggest that severe disease is uncommon in the setting of low anti-K titers and support the use of a critical titer threshold to inform antenatal surveillance. Reevaluation of current clinical guidelines may be warranted in light of these data.

Characterization of severity of hemolytic disease of the fetus and newborn due to Rhesus antigen alloimmunization

BACKGROUND

Clinical manifestations of hemolytic disease of the fetus and newborn include anemia, hyperbilirubinemia, hydrops fetalis, kernicterus, and fetal or neonatal demise. More than 50 antibodies are linked to hemolytic disease of the fetus and newborn, with Rhesus (including D and c) and Kell antigens carrying the highest risk of disease. To date, a multicenter, comprehensive evaluation of hemolytic disease of the fetus and newborn due to Rhesus antigen alloantibodies in the United States has not been undertaken.

OBJECTIVE

This study aimed to implement a novel severity index to characterize the real-world disease spectrum of hemolytic disease of the fetus and newborn due to alloantibodies from the Rhesus class.

STUDY DESIGN

This retrospective cohort study was conducted in neonates with commercial insurance available through Optum's deidentified Clinformatics® Data Mart Database (Clinformatics®) and Merative MarketScan® Commercial Claims and Encounters (CCAE) Database from 2000 to 2022. Neonatal and maternal records were linked algorithmically by shared family identifier. A hierarchical severity index was developed for neonates with a Rhesus antigen hemolytic disease of the fetus and newborn diagnosis code in the first 30 days of life, using antenatal and neonatal diagnoses and treatments: Severe (neonatal death, hydrops fetalis, intrauterine transfusion); Moderate (neonatal exchange transfusion); Mild (neonatal simple transfusion); Minimal (neonatal phototherapy or hyperbilirubinemia). Maternal, antenatal, and perinatal demographic and clinical characteristics were summarized descriptively by severity.

RESULTS

In Clinformatics® and Commercial Claims and Encounters Database, respectively, 1927 and 1268 neonates met the inclusion criteria. Most (93.1% Clinformatics®; 93.5% CCAE Database) displayed minimal severity, although in both databases nearly 40% of these neonates still required phototherapy. More neonates were mildly affected (3.3% Clinformatics®; 2.2% Commercial Claims and Encounters Database) than moderately (1.0% Clinformatics®; 1.1% Commercial Claims and Encounters Database). In Clinformatics® and Commercial Claims and Encounters Database, respectively, severe hemolytic disease of the fetus and newborn affected 2.6% and 3.2% of neonates, 54% and 46% of whom received exchange or simple transfusions. Severely affected neonates were more commonly delivered by cesarean delivery and at a lower gestational age (34.1 weeks Clinformatics®; 35.4 weeks Commercial Claims and Encounters Database) than those minimally affected (38.5 weeks Clinformatics®; 38.4 weeks Commercial Claims and Encounters Database).

CONCLUSION

Results across 2 real-world US databases found that although most neonates affected by hemolytic disease of the fetus and newborn due to Rhesus antigen alloantibodies did not require intervention beyond phototherapy, nearly 7% experienced disease severity requiring invasive intervention or resulting in neonatal mortality. More severely affected neonates had lower gestational age at birth, higher rates of cesarean delivery and neonatal intensive care unit admission, and longer length of hospital stay at birth compared with minimally affected neonates. The HDFN Severity Index is a useful tool to characterize hemolytic disease of the fetus and newborn and may be valuable alongside guideline-driven care in subsequent pregnancies.

Potential of a Second Screening Test for Alloimmunization in Pregnancies of Rhesus-positive Women: A Swedish Population-based Cohort Study

INTRODUCTION

There is lack of consensus regarding whether a second screening in rhesus-positive pregnant women is worthwhile, with different guidelines, recommendations, and practices. We aimed to estimate the number and timing of missed alloimmunizations in rhesus-positive pregnancies screened once and weigh the relative burden of additional screening and monitoring versus the estimated reduction in adverse pregnancy outcomes.

METHODS

We extracted information on maternal, pregnancy, and screening results for 682,126 pregnancies for 2003-2012 from Swedish national registers. We used data from counties with a routine second screening to develop and validate a logistic model for a positive second test after an earlier negative. We used this model to predict the number of missed alloimmunizations in counties offering only one screening. Interval-censored survival analysis identified an optimal time window for a second test. We compared the burden of additional screening with estimated adverse pregnancy outcomes avoided.

RESULTS

The model provided an accurate estimate of positive tests at the second screening. For counties with the lowest screening rates, we estimated that a second screening would increase the alloimmunization prevalence by 33% (from 0.19% to 0.25%), detecting the 25% (304/1222) of cases that are currently missed. The suggested timing of a second screen was gestational week 28. For pregnancies currently screened once, the estimated cost of a second test followed by maternal monitoring was approximately 10% of the cost incurred by the excess adverse pregnancy outcomes.

CONCLUSION

Investment in routine second screening can identify many alloimmunizations that currently go undetected or are detected late, with the potential for cost savings.

Safety of Intrauterine Transfusion Performed Beyond 34 weeks of Gestation

OBJECTIVE

To describe (1) procedure-related complications, and (2) gestational age (GA) at delivery in patients who received their final intrauterine transfusion (IUT) at ≥ 34 weeks 0 days versus at < 34 weeks 0 days.

METHODS

This was a retrospective study of pregnancies treated with IUT. Procedure-related complications were defined as any of the following within 48 h of IUT: (1) rupture of membranes or preterm delivery, (2) intrauterine infection, (3) fetal death, (4) fetal compromise resulting in emergency cesarean, or (5) neonatal death. Patient and procedural characteristics were described among patients with final IUT at ≥ 34 weeks 0 days and at < 34 weeks 0 days.

RESULTS

We studied 94 pregnancies with 237 IUTs; 35 (37.2%) had their last IUT at ≥ 34 weeks 0 days and 59 (62.8%) had their last IUT at < 34 weeks 0 days. Three procedure-related complications occurred (1.3% of procedures, 3.2% of pregnancies). All resulted in emergency cesarean section; 1 case performed at < 34 weeks 0 days resulted in neonatal death. The remaining 2 occurred during IUT at ≥ 34 weeks 0 days. Pregnancies with the last IUT at ≥ 34 weeks 0 days delivered at a median GA of 37.1 weeks.

CONCLUSIONS

Complications were rare. IUT performed at ≥ 34 weeks 0 days appeared safe.

Hemolytic disease of the fetus and newborn-a perspective of immunohematology

BACKGROUND

Hemolytic disease of the fetus and newborn is a public health problem caused by maternal-fetal incompatibility; no prophylaxis is available for most alloantibodies that induce this disease. This study reviews the literature regarding which antibodies are the most common in maternal plasma and which were involved in hemolytic disease of the fetus and newborn.

METHOD

Seventy-five studies were included in this review using a systematic search. Two independent authors identified studies of interest from the PubMed and SciELO databases.

MAIN RESULTS

Forty-four case reports were identified, of which 11 babies evolved to death. From 17 prevalence studies, the alloimmunization rate was 0.17 % with 161 babies receiving intrauterine transfusions and 23 receiving transfusions after birth. From 28 studies with alloimmunized pregnant women (7616 women), 455 babies received intrauterine transfusions and 21 received transfusions after birth.

CONCLUSION

Rh, Kell, and MNS were the commonest blood systems involved. The geographical distribution of studies shows that as these figures vary between continents, more studies should be performed in different countries. Investing in early diagnosis is important to manage the risks and complications of hemolytic disease of the fetus and newborn.

Management of Red Cell Alloimmunization in Pregnancy

Rhesus immune globulin has resulted in a marked decrease in the prevalence of RhD alloimmunization in pregnancy; however, antibody formation to other red cell antigens continues to occur. Evaluation for the presence of anti-red cell antibodies should be routinely undertaken at the first prenatal visit. If anti-red cell antibodies are detected, consideration of a consultation or referral to a maternal-fetal medicine specialist with experience in the monitoring and treatment of these patients is warranted. Cell-free DNA can be used to determine fetal red cell antigen status to determine whether the pregnancy is at risk of complications from the red cell antibodies. First-time sensitized pregnancies are followed up with serial maternal titers, and, when indicated, serial Doppler assessment of the peak systolic velocity in the middle cerebral artery should be initiated by 16 weeks of gestation. When there is a history of an affected fetus or neonate, maternal titers are less predictive of fetal risk; if the fetus is antigen positive, serial peak systolic velocity in the middle cerebral artery measurements should be initiated by 15 weeks of gestation because intraperitoneal intrauterine blood transfusions can be used at this gestation if needed. The mainstay of fetal therapy involves intrauterine transfusion through ultrasound-directed puncture of the umbilical cord with the direct intravascular injection of red cells. A perinatal survival rate exceeding 95% can be expected at experienced centers. Neonatal phototherapy and "top-up" transfusions attributable to suppressed reticulocytosis often are still required for therapy after delivery.

The role of measuring peak systolic velocity of the middle cerebral artery blood flow and anti-K1 titre during pregnancy to detect foetuses with severe anaemia, foetal hydrops, and the requirement of intrauterine transfusion: A systematic review and meta-analysis

The clinical manifestation of foetal anaemia caused by maternal Kell alloantibodies differs from that caused by non-Kell alloantibodies. Severe anaemia develops in the foetus in the early weeks of gestation; therefore, proper management and early intervention are important. A systematic review and meta-analysis was performed to determine whether the anti-K1 titre can determine the sequelae of Kell alloimmunised pregnancies. Prospective and retrospective cohort studies were used to conduct a systematic review following a comprehensive literature search, in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Studies were screened based on a defined set of inclusion and exclusion criteria. A total of 5143 potential articles were identified. Ten studies were used in the meta-analysis of pregnancy outcomes for a specific anti-K1 titre cut-off. The meta-analysis identified statistical significance for intrauterine transfusion (ARD: 0.351; 95 % CI: 0.593-0.109; p-value = 0.004), hydrops (ARD: 0.808; 95 % CI: 1.145-0.472; p-value <0.001), intrauterine foetal death (ARD: 0.938; 95 % CI:1.344 to -0.533; p-value <0.001) and intrauterine transfusion for Doppler middle cerebral artery >1.5 MoM (ARD: 0.381; 95 % CI:1.079 to -0.317; p-value = 0.285). It was concluded that there is no correlation between anti-K1 titre and Kell sensitised pregnancy outcomes, but monitoring the anti-K1 titre is important to manage the pregnancy and it helps clinicians determine the need for intrauterine transfusions. Doppler middle cerebral artery peak systolic velocity is strongly correlated with foetal anaemia and is an efficient routine method for determining the need for intrauterine transfusions in pregnancies affected by anti-K1.

Standard Compared With Extended Red Blood Cell Antigen Matching for Prevention of Subsequent Hemolytic Disease of the Fetus and Newborn: A Systematic Review

OBJECTIVE

To systematically review and meta-analyze alloimmunization among recipients of red blood cells (RBCs) matched for ABO blood type and Rhesus D (ABO+D) antigen compared with those also matched for c, E, and Kell (cEK).

DATA SOURCES

Four online databases (Medline, Scopus, EMBASE, ClinicalTrials.gov ) were searched from March 28, 2023, to April 1, 2024. The search protocol was peer reviewed and published on PROSPERO ( CRD42023411620 ).

METHODS OF STUDY SELECTION

Studies reporting alloimmunization as the primary outcome among recipients of RBCs matched for ABO+D or additional cEK matching were included. Patients transfused with unmatched RBCs or a mixture of matching regimens were excluded. Risk of bias was assessed with Cochrane Tool to Assess Risk of Bias in Cohort Studies and Tool for Risk of Bias. Random-effects meta-analysis was used to combine effect estimates.

TABULATION, INTEGRATION, AND RESULTS

Ten studies met criteria. Risk of bias was low. Overall, 91,221 patients were transfused, of whom 40,220 (44.1%) received additional cEK-matched RBCs. The overall rate of alloimmunization was 6.2% (95% CI, 2.5-14.9%) for ABO+D-only matching and 1.9% (95% CI, 0.7-5.1%) when cEK was added. Time of follow-up antibody testing ranged from 6 to 18 months after transfusion. Additional cEK match was associated with significantly less alloimmunization compared with standard ABO+D match (odds ratio [OR] 0.37, 95% CI, 0.20-0.69). This association remained when chronically transfused patients were excluded (OR 0.65, 95% CI, 0.54-0.79) and for alloimmunization to c, E, or K antigens only (OR 0.29, 95% CI, 0.18-0.47).

CONCLUSION

Additional cEK RBC matching protocols were associated with lower odds of recipient alloimmunization. Given severe sequelae of alloimmunization in pregnancy, routine cEK matching for transfusion in people with pregnancy potential younger than age 50 years in the United States merits consideration.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42023411620 .

Maternal red blood cell alloimmunization prevalence in the United States

ABSTRACT

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

Why do RhD negative pregnant women still become anti-D immunized despite prophylaxis with anti-D immunoglobulin?

Maternal allo-anti-D in RhD negative pregnant women may cause mild to severe hemolytic disease of the fetus and newborn. Although several other antibodies may also destroy red blood cells of the fetus and newborn, preventive measures with anti-D immunoglobulin are only available for D antigen. Targeted antenatal care together with postpartum prophylaxis with anti-D immunoglobulin has significantly reduced the D-alloimmunization risk. Potentially sensitizing events like trauma to the pregnant abdomen, vaginal bleeding, and amniocentesis may lead to fetomaternal hemorrhage and necessitate additional doses. Despite comprehensive programs with these targeted measures, allo-anti-D is still the most common reason for severe hemolytic disease of the fetus and newborn. Where do we fail then? Here, in this review, I would therefore like to discuss the reasons for D-alloimmunizations hoping that the greater focus will pave the way for further reduction in the number of pregnancy-related allo-anti-Ds.

Use of Low-Titer O-Positive Whole Blood in Female Trauma Patients: A Literature Review, Qualitative Multidisciplinary Analysis of Risk/Benefit, and Guidelines for Its Use as a Universal Product in Hemorrhagic Shock

BACKGROUND

Whole blood transfusion is associated with benefits including improved survival, coagulopathy, and decreased transfusion requirements. The majority of whole blood transfusion is in the form of low-titer O-positive whole blood (LTOWB). Practice at many trauma centers withholds the use of LTOWB in women of childbearing potential due to concerns of alloimmunization. The purpose of this article is to review the evidence for LTOWB transfusion in female trauma patients and generate guidelines for its application.

STUDY DESIGN

Literature and evidence for LTOWB transfusion in hemorrhagic shock are reviewed. The rates of alloimmunization and subsequent obstetrical outcomes are compared to the reported outcomes of LTOWB vs other resuscitation media. Literature regarding patient experiences and preferences in regards to the risk of alloimmunization is compared to current trauma practices.

RESULTS

LTOWB has shown improved outcomes in both military and civilian settings. The overall risk of alloimmunization for Rhesus factor (Rh) - female patients in hemorrhagic shock exposed to Rh + blood is low (3% to 20%). Fetal outcomes in Rh-sensitized patients are excellent compared to historical standards, and treatment options continue to expand. The majority of female patients surveyed on the risk of alloimmunization favor receiving Rh + blood products to improve trauma outcomes. Obstetrical transfusion practices have incorporated LTOWB with excellent results.

CONCLUSIONS

The use of whole blood resuscitation in trauma is associated with benefits in the resuscitation of severely injured patients. The rate at which severely injured, Rh-negative patients develop anti-D antibodies is low. Treatments for alloimmunized pregnancies have advanced, with excellent results. Fears of alloimmunization in female patients are likely overstated and may not warrant the withholding of whole blood resuscitation. The benefits of whole blood resuscitation likely outweigh the risks of alloimmunization.

Another piece of the hemolytic disease of the fetus and newborn puzzle after RhD-positive transfusion in trauma resuscitation: the proportion of pregnant women who produce high titer anti-D

Background

After the transfusion of RhD-positive red blood cell (RBC)-containing products to an RhD-negative woman of childbearing potential (WCP) during trauma resuscitation, there are several events that must occur for that WCP to have a future pregnancy affected by hemolytic disease of the fetus and newborn (HDFN). This study identified and quantitated the frequency of a novel event in the sequence from RhD-positive transfusion during trauma resuscitation to an HDFN outcome, that is, the development of a high titer anti-D among women who were D-alloimmunized.

Methods

The transfusion service records at one maternity hospital were searched to locate all anti-D titers that had been performed on pregnant women between 1996 and 2022. The highest titer score during each pregnancy was recorded for this study. The critical titer threshold at this institution was ≥16. Passive anti-D caused by Rh immunoglobulin were excluded from analysis.

Results

There were 97 pregnancies in 85 patients who had an immune-stimulated anti-D; in 60 of 97 (62%) pregnancies, the highest titer score was ≥16. There were 12 patients who had titers performed in two pregnancies during the study period; the correlation between the maximum titer in each pregnancy was not statistically significant (Spearman rank correlation r=0.42, p=0.17).

Conclusion

In this single center study, 62% of D-alloimmunized pregnant women had a high titer antibody. When considering all of the events that must occur for HDFN to happen, the rate of perinatal mortality was calculated to be 0.04% and the rate of perinatal death or serious adverse event from HDFN was 0.24%.

Comparison of automated solid phase versus manual saline indirect antiglobulin test methodology for non-ABO antibody titration: Implications for perinatal antibody monitoring

BACKGROUND

Accurate antibody titration is crucial in prenatal evaluations to identify patients who need clinical monitoring for hemolytic disease of the fetus and newborn (HDFN) causing fetal anemia. This study compares the established gold standard method of manual tube saline indirect antiglobulin testing (SIAT) with the newer automated solid phase (ASP) method of antibody titration and aims to establish the critical titer threshold for ASP that corresponds to the previously established SIAT critical threshold of ≥16 used in our laboratory.

STUDY DESIGN AND METHODS

One hundred fifty-seven prenatal and donor plasma samples with known antibodies were tested using both SIAT and ASP methodologies and results were compared.

RESULTS

The study found that ASP titers were, on average, 1.33 dilutions higher than SIAT titers. The critical titer cutoff for ASP was determined to be ≥32, which is one tube higher than the SIAT cutoff of ≥16.

DISCUSSION

The ASP method for antibody titration offers greater reproducibility and efficiency compared with manual SIAT titration. This study suggests that a titer cutoff of ≥32 is appropriate for most clinically significant antibodies using ASP. However, further research is needed to determine the comparability of ASP with SIAT in samples with multiple antibodies, anti-M antibodies, and other less common antibodies. Validation of the ASP titer cutoff against HDFN clinical outcomes is required before implementing this test for routine use in perinatal antibody titration.

Validation of a non-invasive prenatal test for fetal RhD, C, c, E, K and Fya antigens

We developed and validated a next generation sequencing-(NGS) based NIPT assay using quantitative counting template (QCT) technology to detect RhD, C, c, E, K (Kell), and Fya (Duffy) fetal antigen genotypes from maternal blood samples in the ethnically diverse U.S. population. Quantitative counting template (QCT) technology is utilized to enable quantification and detection of paternally derived fetal antigen alleles in cell-free DNA with high sensitivity and specificity. In an analytical validation, fetal antigen status was determined for 1061 preclinical samples with a sensitivity of 100% (95% CI 99-100%) and specificity of 100% (95% CI 99-100%). Independent analysis of two duplicate plasma samples was conducted for 1683 clinical samples, demonstrating precision of 99.9%. Importantly, in clinical practice the no-results rate was 0% for 711 RhD-negative non-alloimmunized pregnant people and 0.1% for 769 alloimmunized pregnancies. In a clinical validation, NIPT results were 100% concordant with corresponding neonatal antigen genotype/serology for 23 RhD-negative pregnant individuals and 93 antigen evaluations in 30 alloimmunized pregnancies. Overall, this NGS-based fetal antigen NIPT assay had high performance that was comparable to invasive diagnostic assays in a validation study of a diverse U.S. population as early as 10 weeks of gestation, without the need for a sample from the biological partner. These results suggest that NGS-based fetal antigen NIPT may identify more fetuses at risk for hemolytic disease than current clinical practice, which relies on paternal genotyping and invasive diagnostics and therefore is limited by adherence rates and incorrect results due to non-paternity. Clinical adoption of NIPT for the detection of fetal antigens for both alloimmunized and RhD-negative non-alloimmunized pregnant individuals may streamline care and reduce unnecessary treatment, monitoring, and patient anxiety.

Neonatal outcomes following intrauterine transfusion for hemolytic disease of the fetus and newborn: a twenty-year service review

OBJECTIVE

The primary objective was to explore perinatal and neonatal outcomes amongst infants who received intrauterine transfusion (IUT) for the management of hemolytic disease of the fetus and newborn (HDFN). The secondary objective was to evaluate the role of key investigations in the fetus at risk of HDFN and assess the relationship with neonatal outcomes. We hypothesized that middle cerebral artery peak systolic velocity (MCA-PSV) and corresponding multiples of the median (MoM) would be predictive of neonatal course.

METHODS

This was a retrospective observational study conducted at a tertiary center in the United Kingdom between January 2000 and August 2020. Trust approval was obtained to conduct this service review. Pregnancies requiring IUT for HDFN were identified using the fetal medicine department database. Inclusion criteria were infants who received IUT for HDFN. 67 pregnancies were eligible for inclusion in the study with 156 IUT events. Data were extracted using healthcare records. Statistical analysis was performed using SPSS version 28.0, data were assessed for normality and Spearman's correlation analysis was performed with p values < .05 considered significant.

RESULTS

67 pregnancies were included in the study which led to the live birth of 68 infants (one twin pregnancy). There were no fetal deaths following IUT. There was one neonatal death due to extreme prematurity following spontaneous vaginal delivery at 23 + 4 weeks gestation, occurring three days following IUT. 97% of infants required admission to the neonatal intensive care unit and 88% required phototherapy. 25% of infants required readmission for red blood cell transfusion due to anemia. There was a significant correlation between maternal anti-D antibody levels and length of neonatal admission r = 0.477, p = .014. MCA-PSV and MoM measured prior to the last IUT had a significant positive correlation with the duration of phototherapy: r = 0.527 (p < .001) and r = 0.313 (p < .05) respectively. Linear regression analysis demonstrated a significant positive relationship between MCA-PSV and corresponding MoM recorded prior to the last IUT with r²= 0.177 (p = .003) and r²= 0.101 (p = .029).

CONCLUSION

HDFN is an important cause of fetal anemia associated with significant neonatal morbidity. MCA-PSV and MoM may be predictive of neonatal phototherapy requirements. The predictive value of MCA-PSV appears to be dependent on the timing of measurement during the antenatal period and more research is needed. Multicentre collaboration is required to generate a reliable large-scale database to further delineate the value of MCA-PSV and MoM and predict neonatal outcomes in cases of HDFN requiring IUT. This data would assist clinicians in antenatal planning and enable more informed counseling of parents in the antenatal period.

Population-based incidence and risk factors for cholestasis in hemolytic disease of the fetus and newborn

OBJECTIVE

To estimate the incidence of cholestasis in neonates with hemolytic disease of the fetus and newborn (HDFN) and investigate risk factors and long-term liver disease.

STUDY DESIGN

A population-based cohort study of all infants born with HDFN within the Stockholm region between 2006 and 2015. The study period was the first 90 days of life, and presence of any chronic liver disease was evaluated at two years of age.

RESULTS

Cholestasis occurred in 7% (11/149). Median age at detection was 1.1 days. Intrauterine blood transfusions and maternal alloimmunization with multiple red blood cell antibodies including D-, c- or K-antibodies were independent risk factors for cholestasis. No infant had chronic liver disease at two years of age.

CONCLUSIONS

Infants with severe HDFN have increased risk for cholestasis, particularly those requiring multiple intrauterine transfusions. Early and repeated screening for conjugated hyperbilirubinemia in the first week of life is needed to ensure adequate management.