Detection of fetal hemorrhage in Rh immune globulin candidates. A rosetting technique using enzyme-treated Rh2Rh2 indicator erythrocytes

Use of a Monocyte Monolayer Assay to Evaluate Fcγ Receptor-mediated Phagocytosis

Although originally developed for predicting transfusion outcomes of serologically incompatible blood, the monocyte monolayer assay (MMA) is a highly versatile in vitro assay that can be modified to examine different aspects of antibody and Fcγ receptor (FcγR)-mediated phagocytosis in both research and clinical settings. The assay utilizes adherent monocytes from peripheral blood mononuclear cells isolated from mammalian whole blood. MMA has been described for use in both human and murine investigations. These monocytes express FcγRs (e.g., FcγRI, FcγRIIA, FcγRIIB, and FcγRIIIA) that are involved in immune responses. The MMA exploits the mechanism of FcγR-mediated interactions, phagocytosis in particular, where antibody-sensitized red blood cells (RBCs) adhere to and/or activate FcγRs and are subsequently phagocytosed by the monocytes. In vivo, primarily tissue macrophages found in the spleen and liver carry out FcγR-mediated phagocytosis of antibody-opsonized RBCs, causing extravascular hemolysis. By evaluating the level of phagocytosis using the MMA, different aspects of the in vivo FcγR-mediated process can be investigated. Some applications of the MMA include predicting the clinical relevance of allo- or autoantibodies in a transfusion setting, assessing candidate drugs that promote or inhibit phagocytosis, and combining the assay with fluorescent microscopy or traditional Western immunoblotting to investigate the downstream signaling effects of FcγR-engaging drugs or antibodies. Some limitations include the laboriousness of this technique, which takes a full day from start to finish, and the requirement of research ethics approval in order to work with mammalian blood. However, with diligence and adequate training, the MMA results can be obtained within a 24-h turnover time.

Accurate quantitation of D+ fetomaternal hemorrhage by flow cytometry using a novel reagent to eliminate granulocytes from analysis

BACKGROUND

Quantitation of fetomaternal hemorrhage (FMH) is performed to determine the dose of prophylactic anti-D (RhIG) required to prevent D immunization of D- women. Flow cytometry (FC) is the most accurate method. However, maternal white blood cells (WBCs) can give high background by binding anti-D nonspecifically, compromising accuracy.

STUDY DESIGN AND METHODS

Maternal blood samples (69) were sent for FC quantitation of FMH after positive Kleihauer-Betke test (KBT) analysis and RhIG administration. Reagents used were BRAD-3-fluorescein isothiocyanate (FITC; anti-D), AEVZ5.3-FITC (anti-varicella zoster [anti-VZ], negative control), anti-fetal hemoglobin (HbF)-FITC, blended two-color reagents, BRAD-3-FITC/anti-CD45-phycoerythrin (PE; anti-D/L), and BRAD-3-FITC/anti-CD66b-PE (anti-D/G). PE-positive WBCs were eliminated from analysis by gating. Full blood counts were performed on maternal samples and female donors.

RESULTS

Elevated numbers of neutrophils were present in 80% of patients. Red blood cell (RBC) indices varied widely in maternal blood. D+ FMH values obtained with anti-D/L, anti-D/G, and anti-HbF-FITC were very similar (r = 0.99, p < 0.001). Correlation between KBT and anti-HbF-FITC FMH results was low (r = 0.716). Inaccurate FMH quantitation using the current method (anti-D minus anti-VZ) occurred with 71% samples having less than 15 mL of D+ FMH (RBCs) and insufficient RhIG calculated for 9%. Using two-color reagents and anti-HbF-FITC, approximately 30% patients had elevated F cells, 26% had no fetal cells, 6% had D- FMH, 26% had 4 to 15 mL of D+ FMH, and 12% patients had more than 15 mL of D+ FMH (RBCs) requiring more than 300 μg of RhIG.

CONCLUSION

Without accurate quantitation of D+ FMH by FC, some women would receive inappropriate or inadequate anti-D prophylaxis. The latter may be at risk of immunization leading to hemolytic disease of the newborn.

Survey on the prevention and incidence of haemolytic disease of the newborn in Italy

BACKGROUND

In 2010, the Italian Society of Immunohaematology and Transfusion Medicine (SIMTI) carried out a survey of the incidence of haemolytic disease of the newborn (HDN) and the prevention of HDN caused by anti-Rh(D) in Italian Transfusion Structures (TS).

MATERIALS AND METHODS

A questionnaire divided into the following five sections was administered: (i) types of services provided and maintenance of legally required registers, (ii) immunoprophylaxis (IP), (iii) red cell typing and searches for irregular antibodies, (iv) evaluation of foetal-maternal haemorrhage (FMH), and (v) incidence of HDN in 2010. Of the 280 TS sent the questionnaire, 176 (63%) replied.

RESULTS

A HDN register was available in 55.5% of the TS (n =91). Immunoprophylaxis with a dose of anti-D IgG was given to all Rh(D) negative and Rh(D) variant puerpera with Rh(D) positive newborns: in more than 93% of cases the dose was between 1,500 IU (300 μg) and 1,250 IU (250 μg). Antenatal IP between the 25(th) and 28(th) week was proposed by 42 TS (26%). Seventy percent of the TS (n =115) did not make any evaluation of FMH. The number of births surveyed in 2010 was 203,384, the number of Rh(D) negative pregnancies was 13,569, while anti-D antibodies were present in 245 pregnancies. There were 111 cases of HDN due to anti Rh(D) incompatibility and in 40 of these, intrauterine transfusion (n =8) or exchange transfusion (n =32) was necessary. In 94 cases HDN was due to other irregular antibodies: in 4 of these cases intrauterine transfusion was needed and in 11 other recourse was made of exchange transfusion. Finally, there were 1,456 newborns with ABO HDN of whom 13 underwent exchange transfusion.

DISCUSSION

The data collected give a picture of the incidence of HDN in Italy and of the methods of managing IP and could form the basis for an update of the SIMTI recommendations on the management and prevention of this disease.

Detection of fetomaternal hemorrhage

The prevention of Rhesus D alloimmunization through Rh immune globulin (RhIg) administration is the major indication for the accurate detection and quantification of fetomaternal hemorrhage (FMH). In the setting of D incompatibility, D-positive fetal cells can sensitize the D-negative mother, resulting in maternal anti-D alloantibody production. These anti-D alloantibodies may lead to undesirable sequelae such as hemolytic disease of the newborn (HDN). Since the widespread adoption of FMH screening and RhIg immunoprophylaxis, the overall risk of Rh alloimmunization and infant mortality from HDN has substantially decreased. The rosette screen, the initial test of choice, is highly sensitive in qualitatively detecting 10 mL of fetal whole blood in the maternal circulation. As the screen is reliant on the presence of the D antigen to distinguish fetal from maternal cells, it cannot be used to detect FMH in D-positive mothers or in D-negative mothers carrying a D-negative fetus. The Kleihauer-Betke acid-elution test, the most widely used confirmatory test for quantifying FMH, relies on the principle that fetal RBCs contain mostly fetal hemoglobin (HbF), which is resistant to acid-elution whereas adult hemoglobin is acid-sensitive. Although the Kleihauer-Betke test is inexpensive and requires no special equipment, it lacks standardization and precision, and may not be accurate in conditions with elevated F-cells. Anti-HbF flow cytometry is a promising alternative, although its use is limited by equipment and staffing costs. Hematology analyzers with flow cytometry capabilities may be adapted for fetal cell detection, thus giving clinical laboratories a potentially attractive automated alternative for quantifying FMH.

Inaccurate doses of R immune globulin after rh-incompatible fetomaternal hemorrhage: survey of laboratory practice

CONTEXT

Rh(D)-negative women with a large fetomaternal hemorrhage (FMH) from an Rh(D)-positive fetus are at risk for anti-D alloimmunization if they do not receive adequate Rh immune globulin (RhIG). Determination of the adequate RhIG dose for these women is a critical laboratory procedure for protecting their future Rh(D)-positive children.

OBJECTIVE

To determine how often laboratories recommended an inaccurate dose of RhIG for excess FMH.

DESIGN

Nearly 1600 laboratories using the College of American Pathologists' proficiency testing for fetal red blood cell detection were surveyed to determine (1) their calculation method and (2) the number of RhIG doses recommended for a survey specimen, based on their measured percentage of fetal red blood cells. We surveyed nearly 1450 laboratories for their accuracy in determining RhIG dose, using 2 common calculation methods we provided.

RESULTS

The AABB Technical Manual method was used by 67% of responding laboratories. However, 20.7% of laboratories using this method would have recommended an inaccurate dose of RhIG--11.5% too much and 9.2% too little--for the level of FMH reported in the survey specimen. If all laboratories had used the common recommendation of 300 microg/30 mL of fetal blood present, 2% would have recommended RhIG doses too low for the volume of FMH they measured. In 3 of the 4 calculation exercises we provided, 20% to 30% of laboratories underestimated the necessary dose of RhIG.

CONCLUSIONS

Based on our surveys, some mothers with excess FMH may be receiving inaccurate doses of RhIG. Laboratories performing quantification of FMH should review their procedures and training for calculating RhIG dosage.

A survey of the current use of anti-D immunoprophylaxis and the incidence of haemolytic disease of the newborn in Italy

INTRODUCTION

The Italian Society of Transfusion Medicine and Immunohaematology (SIMTI) carried out a survey on the current use of anti-D immunoprophylaxis (IP) in Italy, on its ways of use and on the impact that it has had on decreasing haemolytic disease of the newborn (HDN), due to maternal-foetal incompatibility for the D antigen.

MATERIALS AND METHODS

The survey was carried out using a questionnaire prepared by the Working Group established for this purpose by the SIMTI. The questions were divided into five groups: the ways of carrying out IP, evaluation of foetal-maternal haemorrhage, serological tests after IP, the current incidence of HDN, and data on exchange transfusions.

RESULTS

Data were obtained from 69 Transfusion Services (TS). Four of these give IP antenatally, whereas in the remaining cases IP is given after birth. Almost all the TS evaluate the amount of foetal-maternal haemorrhage in order to give additional doses of anti-D IgG, with the most widely used method being the Kleihauer-Betke test. Data were collected from 176,010 pregnancies: 18,639 were D-negative women, of whom 18,440 were not immunised. There were 136 cases of HDN with anti-D antibodies, and 39 of these required exchange transfusions (ET). Furthermore, there were 1,535 pregnant women with anti-A and/or anti-B IgG, which were clinically significant in 83 and required ET in 37. Finally, 40 women had antibodies, directly related to the pregnancy, against antigens other than D (in eight of these cases ET was necessary).

CONCLUSIONS

The survey carried out by SIMTI was able to give a sufficiently full and accurate picture of current Italian practices concerning the use and ways of use of anti-D IP in pregnancy and the puerperum, as well as the incidence and characteristics of HDN. Furthermore, this survey was the basis for guidelines on the management of HDN, produced by SIMTI in collaboration with the Italian Society of Obstetricians and Gynaecologists.

Chorionic villus sampling for fetal Rh typing: clinical implications

OBJECTIVE

The prenatal Rh typing of red blood cells obtained by chorionic villus sampling was performed with an immune rosette technique.

STUDY DESIGN

Ten Rh-negative pregnant women undergoing chorionic villus sampling at 9 to 11 weeks' gestation were studied at a large referral hospital.

RESULTS

Accurate Rh phenotyping may be done on red blood cells obtained from chorionic villi weighing 2 to 8 mg. The preparations were shown to be greater than 90% fetal in origin as demonstrated by radial immunodiffusion quantitation of fetal hemoglobin-containing cells. Of the 10 fetuses typed in the first trimester nine of the pregnancies were carried to term. In all cases typing of red blood cells confirmed the antenatal fetal red cell typing.

CONCLUSIONS

This study shows that antenatal Rh phenotyping may be performed as early as 9 to 11 weeks' gestation. This technique may be used in the management of pregnancies complicated by Rh incompatibility.

Overestimation of fetomaternal haemorrhage by the acid-elution technique in mothers with beta-thalassaemia minor

In Rh-negative women, it is important to quantify the magnitude of an Rh-positive fetomaternal haemorrhage (FMH) so that sufficient Rh immune globulin (RhIg) can be administered early in the post-partum period to prevent alloimmunization. The standard post-partum dose of RhIg varies from 100 micrograms in the UK to 300 micrograms in North America. It is therefore important to identify all Rh-negative women who have had an FMH greater than 10 ml in the UK or greater than 30 ml in North America because an FMH greater than these amounts will affect the dose of RhIg that is administered. As acid-elution techniques can overestimate the magnitude of an FMH in the presence of an elevated maternal haemoglobin F level, we performed a prospective study to determine how often this occurred. Of 1,894 consecutive Rh-negative mothers who delivered Rh-positive infants, whose blood was screened for an FMH greater than 10 ml of fetal blood using an acid-elution procedure, 11 were found to have an FMH over 10 ml. In five of these 11 women, the volume of FMH was less than 10 ml using an alternative technique (rosette test) to assess the FMH size. Six of these women were found to have beta-thalassaemia minor on the basis of a low MCV, and high haemoglobin A2 and/or high haemoglobin F levels. In five of these the FMH was significantly overestimated by the acid-elution technique compared to the rosette technique. Therefore, in the presence of a maternal condition, which may result in an elevated haemoglobin F level, an FMH estimated to be over 10 ml in the UK or 30 ml in North America using an acid-elution procedure, should be confirmed by an alternative technique, which does not involve the estimation, directly or indirectly, of haemoglobin F.

The incidence of significant fetomaternal hemorrhage in patients undergoing cesarean section

To determine the incidence of fetomaternal hemorrhage in patients undergoing cesarean section, Kleihauer-Betke tests were performed in the immediate postoperative period on 199 parturients. Some degree of hemorrhage was detected in 18.5% of patients, with 2.5% demonstrating greater than 30 ml of fetal blood. Comparison of groups on the basis of indication for cesarean delivery revealed no difference in rates of fetal hemorrhage. Because patients with greater than 30 ml of fetal blood would not be adequately protected from Rh sensitization by the standard 300 micrograms dose of Rh immune globulin, we recommend screening all Rh-negative patients undergoing cesarean section for the presence of significant fetomaternal hemorrhage.

Assessment of fetal-maternal haemorrhage in mothers with hereditary persistence of fetal haemoglobin

Kleihauer examination of peripheral blood cannot be used reliably to detect transplacental fetal-maternal haemorrhage in mothers with hereditary persistence of fetal haemoglobin (HPFH). In Rh(D) negative pregnancies diagnostic confusion with a large fetal-maternal haemorrhage could result in the administration of inappropriately excessive amounts of anti-D immunoglobulin, and the inability to diagnose and quantify transplacental haemorrhage in maternal HPFH by current methods could result in insufficient anti-D administration and subsequent Rh(D) sensitisation. Accordingly, a method to detect and quantify fetal-Rh(D) positive maternal haemorrhage using erythrocyte fluorescent immunocytometry was developed. An indirect immunofluorescence method with IgG anti-D immunoglobulin as the primary antibody was used, combined with quantitative analysis on a fluorescence activated cell sorter. The method was accurate, specific, and sensitive and could detect a contaminating population of 0.1% Rh(D) positive cells in Rh(D) negative blood--a level of fetal-maternal haemorrhage well covered by a single dose of 500 IU of anti-D immunoglobulin.

Flow cytometry: its applications to immunohaematology

Flow cytometry, using fluorescent probes, has only recently been applied to practical aspects of immunohaematology. It has been used for the detection and quantitation of cell-bound immunoglobulins and complement, minor cell populations, cellular antigens, and platelet and granulocyte antibodies. Practical applications of detecting minor cell populations have been successful in determining the extent of fetal maternal haemorrhage; determining the survival of transfused RBCs (small and large volumes); demonstrating RBC chimaerism (e.g. following bone marrow transplantation) and RBC mosaicism (e.g. demonstration of the McLeod phenotype carrier status). A large variety of cellular antigens have been demonstrated on RBCs, platelets and white cells using flow cytometry. Quantitation of RBC antigens by flow cytometry has been found to be much more objective and accurate than the routinely used serological approaches for establishing zygosity in paternity studies. Flow cytometry has been found to be a sensitive, objective and reproducible method for detecting platelet auto-and alloantibodies, and has also been used to detect granulocyte antibodies. More recently, it has been used to detect antibodies to monocytes and lymphocytes. As flow cytometers become more commonly available, many of these applications may become routine in clinical pathology laboratories.

Fetal blood group determination in first-trimester pregnancy for the management of severe immunization

The presence or absence of Rho (D) and Kell antigens on fetal red blood cells was determined in the first trimester of pregnancy on erythrocytes obtained by chorionic villi sampling with the use of mixed agglutination and solid phase microimmunofluorescence techniques. Pregnancies in one Kell-sensitized woman and seven severely RH-sensitized women with a poor obstetric history and a partner heterozygous for the offending antigen were examined. A conclusive diagnosis could be made in seven of the eight cases studied.

Clinical high-risk designation does not predict excess fetal-maternal hemorrhage

During a 5-year period, an enzyme-linked antiglobulin test was used to screen and quantitate fetal-maternal hemorrhage in 789 consecutive D-negative mothers who were delivered of D-positive babies. Six hundred seventy-two patients (85.2%) had no detectable fetal-maternal hemorrhage, and 117 patients (14.8%) had a detectable fetal-maternal hemorrhage. Eight of the 789 (1%) had a fetal-maternal hemorrhage greater than 30 ml and required more than one vial of Rh immune globulin. Two patients with fetal-maternal hemorrhage of 29 and 30 ml also received additional Rh immune globulin. Each case was reviewed for the presence of high-risk features that are thought to predict patients at risk for fetal-maternal hemorrhage. Patients having a cesarean section or complicated vaginal delivery were considered to be in a group at high risk for fetal-maternal hemorrhage, while those with a spontaneous vaginal delivery were considered not to be at risk for fetal-maternal hemorrhage. Thirty-two of 237 patients (13.5%) in the risk group and 82 of 552 patients (15.3%) in the group not at risk had detectable fetal-maternal hemorrhage. The incidence of fetal-maternal hemorrhage for these two groups was not statistically different (p greater than 0.50 by chi 2 analysis). If only patients in the risk group had been screened for fetal-maternal hemorrhage, then five of 10 (50%) who required more than one vial of Rh immune globulin would have been undertreated and at risk for developing anti-D antibodies. In addition, newborn birth weight, Apgar scores, and hematocrits were examined for 13 cases of fetal-maternal hemorrhage of greater than or equal to 21 ml, and none of these characteristics could be used to predict patients at risk for fetal-maternal hemorrhage. Therefore, no maternal or newborn characteristics could be identified that would reliably predict patients at risk for fetal-maternal hemorrhage. We conclude that all D-negative patients with D-positive babies should continue to be screened for fetal-maternal hemorrhage to identify those patients requiring more than one vial of Rh immune globulin.

ABO and Rhesus phenotyping of fetal erythrocytes in the first trimester of pregnancy

Determination of fetal red blood cell antigens in early pregnancy can be important in cases with a history of severe haemolytic disease of the newborn. From chorionic villus biopsies (CVB) between the 8th and 12th week of gestation a small number of fetal red blood cells was obtained, inevitably highly contaminated with maternal blood cells. Two techniques were used to demonstrate the minor (fetal) cell population with a blood group antigen differing from the major (maternal) cell population: a solid-phase microfluorescence technique (introduced in this paper) which was compared with the mixed agglutination technique. In series of artificial mixtures of erythrocytes it was shown that with the microfluorescence technique the ABO and Rhesus phenotypes of minor cell populations could be determined at a ratio of 1 in 4000 erythrocytes of the major population, making this technique 4 times as sensitive as the mixed agglutination technique. We further investigated the reliability of the microfluorescence technique to demonstrate antagonistic fetal blood groups in the first trimester of pregnancy. Of 18 women undergoing CVB prior to therapeutic abortion, blood group antagonism (ABO and Rhesus systems) was demonstrate in all 11 cases in which it was present. Therefore, it seems that CVB can be reliably used for the prenatal diagnosis of (recurrent) blood group antagonism.

Use of the erythrocyte rosette test to screen for excessive fetomaternal hemorrhage in Rh-negative women

The possibility of Rh immune globulin failure exists when a fetomaternal hemorrhage exceeds 25 to 30 ml of whole blood and only one 300 micrograms vial of Rh immune globulin is administered. In this prospective study of 1000 consecutive Rh-negative women who were delivered of Rh-positive newborn infants, the presence of fetal erythrocytes in maternal blood was identified with use of both the Du test read microscopically and the erythrocyte rosette test. All positive tests prompted fetomaternal hemorrhage quantification with use of a modified Kleihauer-Betke acid elution test. Nineteen patients demonstrated a positive rosette test, and the only positive Du tests were in five of these 19. Six of the nineteen had levels of greater than 30 ml of whole blood for an incidence of 0.6% for fetomaternal hemorrhage exceeding the protective capabilities of the standard Rh immune globulin dosage. In experiments with simulated fetomaternal hemorrhage, all 79 samples, containing from 2.5 to 70 ml of fetal whole blood, were positive according to the erythrocyte rosette test. Applying the Du test to the same samples resulted in a 30% false negative rate at the level of a 30 ml simulated hemorrhage. Based on sufficient sensitivity, ease of interpretation, and reasonable cost, the rosette test appears to be a superior screening test for excessive fetomaternal hemorrhage in Rh immune globulin candidates.

The Du phenotype, serology, and clinical relevance

In this article, the authors examine the nature of the Du phenomenon through a comprehensive historical review beginning with the initial description of the Du factor in the 1940s. Pertinent developments in serologic testing methods and genetic concepts are described. Evidence of the importance of the Du factor in transfusion and hemolytic disease of the newborn is also presented. Selected articles on the frequency of Du in Caucasian and Negro populations are cited. Finally, the authors review current theoretical concepts concerning the nature of the Du factor, its importance in current transfusion practice and maternal Rh immune globulin administration, and the use of microscopic Du testing as a screening procedure for fetomaternal hemorrhage.