Prenatal and perinatal immunohematology: recommendations for serologic management of the fetus, newborn infant, and obstetric patient

Antibody Titers in Transfusion Medicine: A Critical Reevaluation of Testing Accuracy, Reliability, and Clinical Use

CONTEXT.—

Substantial variability between different antibody titration methods has been identified since the development and introduction of the uniform procedure in 2008.

OBJECTIVE.—

To determine whether more recent methods or techniques decrease interlaboratory and intralaboratory variation measured using proficiency testing.

DESIGN.—

Proficiency test data for antibody titration between 2014 and 2018 were obtained from the College of American Pathologists. Interlaboratory and intralaboratory variations were compared by analyzing the distribution of titer results by method and phase, comparing the results against the supplier's quality control titer, and by evaluating the distribution of paired titer results when each laboratory received a sample with the same titer twice.

RESULTS.—

A total of 1337 laboratories participated in the antibody titer proficiency test during the study period. Only 54.1% (5874 of 10 852) of anti-D and 63.4% (3603 of 5680) of anti-A reported responses were within 1 titer of the supplier's intended result. Review of the agreement between laboratories of the same methodology found that 78.4% (3139 of 4004) for anti-A and 89.0% (9655 of 10 852) of laboratory responses for anti-D fell within 1 titer of the mode response. When provided with 2 consecutive samples of the same titer (anti-D titer: 16), 85% (367 of 434) of laboratories using the uniform procedure and 80% (458 of 576) using the other method reported a titer difference of 1 or less.

CONCLUSIONS.—

Despite advances, interlaboratory and intralaboratory variance for this assay remains high in comparison with the strong reliance on titer results in clinical practice. There needs to be a reevaluation of the role of this test in clinical decision-making.

Reassessment of Critical Anti-D Antibody Titer in RhD Alloimmunized Antenatal Women

OBJECTIVE

In the setting of RhD-alloimmunized pregnancy, laboratory variations in critical titer (CT) of anti-D antibody may result in needless referrals or a compromised fetal outcome.

METHODS

RhD-alloimmunized pregnant women were included. Fetal outcome was categorized based on cord hemoglobin and interventions required. For 3 commonly used CTs of 8, 16, and 32, sensitivity and specificity as well as positive and negative predictive values were computed.

RESULTS

When compared with CTs of 16 and 32, we detected 6.9% and 19.4% more cases of moderate-severe hemolytic disease of the fetus and newborn by using 8 as the CT. However, this leads to greater rate of unnecessary referral (12.1%, 10/82) than a CT of 16 (8.2%, 6/73) and 32 (4.9%, 3/61). A CT of 8 demonstrated 100% sensitivity, but 12.1% (10/82) of patients were referred needlessly.

CONCLUSION

Because of its 100% sensitivity, we advocate decreasing the CT to 8. However, this may lead to unwarranted referrals.

Retrospection of Anti-Blood Group Antibody Proficiency Testing Data Using the Geometric Mean and Standard Deviation

OBJECTIVES

We reanalyzed the data from proficiency testing (PT) to assess the effect of the geometric mean in the statistical analysis of immunohematologic data.

METHODS

Using the five most recent anti-blood group antibody titer participant summary results, the geometric mean (GM) ±2 × geometric standard deviation (GSD) was used as the comparative consensus criterion to mode ±2 titers.

RESULTS

Using the PT evaluation criterion of mode ±2 titers, the mean percentages of participants with acceptable results were 97.5% and 97.8% for anti-A and anti-D, respectively. When applying GM ±2 GSD, the mean percentages of acceptable results were 96.1% (anti-A) and 96.1% (anti-D). The percentages of responses included in each consensus criterion were lower using GM ±2 GSD, with a few exceptions.

CONCLUSIONS

Geometric means are more robust and precise in visualizing the central tendency. This method can improve the statistical robustness of PT evaluations.

Impact of Uniform Methods on Interlaboratory Antibody Titration Variability: Antibody Titration and Uniform Methods

Context.—Substantial variability between different antibody titration methods prompted development and introduction of uniform methods in 2008.

Objective.—To determine whether uniform methods consistently decrease interlaboratory variation in proficiency testing.

Design.—Proficiency testing data for antibody titration between 2009 and 2013 were obtained from the College of American Pathologists. Each laboratory was supplied plasma and red cells to determine anti-A and anti-D antibody titers by their standard method: gel or tube by uniform or other methods at different testing phases (immediate spin and/or room temperature [anti-A], and/or anti-human globulin [AHG: anti-A and anti-D]) with different additives. Interlaboratory variations were compared by analyzing the distribution of titer results by method and phase.

Results.—A median of 574 and 1100 responses were reported for anti-A and anti-D antibody titers, respectively, during a 5-year period. The 3 most frequent (median) methods performed for anti-A antibody were uniform tube room temperature (147.5; range, 119–159), uniform tube AHG (143.5; range, 134–150), and other tube AHG (97; range, 82–116); for anti-D antibody, the methods were other tube (451; range, 431–465), uniform tube (404; range, 382–462), and uniform gel (137; range, 121–153). Of the larger reported methods, uniform gel AHG phase for anti-A and anti-D antibodies had the most participants with the same result (mode). For anti-A antibody, 0 of 8 (uniform versus other tube room temperature) and 1 of 8 (uniform versus other tube AHG), and for anti-D antibody, 0 of 8 (uniform versus other tube) and 0 of 8 (uniform versus other gel) proficiency tests showed significant titer variability reduction.

Conclusion.—Uniform methods harmonize laboratory techniques but rarely reduce interlaboratory titer variance in comparison with other methods.

Prevalence, Specificity and Titration of Red Cell Alloantibodies in Multiparous Antenatal Females at a Tertiary Care Centre from North India

Screening and detection of clinically significant antibodies among antenatal women plays an important role in transfusion safety and preventing hemolytic disease of fetus and newborn. Routine screening of antenatal women for antibodies is not done in all blood centres of our country and so immunization rates are not known in pregnant women. We studied the prevalence of alloantibodies and titration of Anti D among antenatal multiparous women in Jammu region. In present prospective study, 750 antenatal multiparous women attending antenatal clinics were typed for ABO and D antigens. Alloantibody screening was done, if positive, specificity of alloantibody was ascertained by using commercially available red cell panel by tube method. Rate of alloimmunization was correlated with Rh D status, gravida, previous transfusion history and bad obstetric history. Titration of alloantibody D was done in first and third trimester of pregnancy. In present study most common blood group detected was B positive (38.4 %). Rh D negative cases constituted 7.6 % of total cases. Rate of alloimmunization was 2 %. A significant correlation was seen between Rh D-negative and alloimmunization (21 % in D-negative and 0.45 % in D-positive). There is significant increasing degree of alloimmunization with increase in Gravida. Alloimmunization in females with bad obstetric history was high (4.41 %) as compared to females with no bad obstetric history showing only 1.76 %. Alloantibodies detected were Anti-D, Anti-E, Anti-C and Anti-K. Anti-D constituted 80 % of all alloantibodies detected. Six women in their third trimester had raised titers of anti-D. Most common alloantibody detected was anti-D (80 %). Alloantibodies to other Rh antigens and Kell blood group systems were also identified. To minimize alloimmunization in Rh D negative women, proper Anti D immunoprophylaxis should be implemented.

Identification of neonates at risk for hazardous hyperbilirubinemia: emerging clinical insights

Hyperbilirubinemia is the most common condition requiring evaluation and treatment in neonates. Identifying among all newborns those few at risk to develop marked hyperbilirubinemia is a clinical challenge. Clinical, epidemiologic, and genetic risk factors associated with severe hyperbilirubinemia include late preterm gestational age, exclusive breastfeeding, glucose-6-phosphate dehydrogenase deficiency, ABO hemolytic disease, East Asian ethnicity, jaundice observed in the first 24 hours of life, cephalohematoma or significant bruising, and history of a previous sibling treated with phototherapy. It is increasingly apparent that the etiopathogenesis of severe hyperbilirubinemia is often multifactorial, and emerging evidence suggests that combining risk factor assessment with measurement of predischarge total serum or transcutaneous bilirubin levels will improve hyperbilirubinemia risk prediction.

Reducing the Variation in Performance of Antibody Titrations

Background.—Antibody titration is difficult to standardize. We investigated whether a detailed, uniform procedure for antibody titration would reduce variation in both tube-based and gel card titres in an international study.

Methods.—Laboratories (n = 35) tested proficiency testing material provided by the College of American Pathologists each according to (i) their routine method; (ii) a detailed, uniform method; and (iii) the uniform method titrating the serum sample against a red cell of specified phenotype (D+ C− c+ E+ e− for anti-D; A1 for anti-A) instead of the red cell of the same phenotype provided in the proficiency testing kit. Uniform method results were reported with 1+ and w+ end-points. Paired statistical analyses of variance were conducted using the F-test.

Results.—The variance between laboratories was not significantly reduced with the uniform method using a 1+ end-point. However, a statistically significant reduction in the variance of anti-D and anti-A titres by the tube-based uniform technique after 37°C incubation and conversion to the antiglobulin (AHG) phase was seen when 19 laboratories reanalysed their results using a w+ end-point. Too few laboratories reported results with a w+ end-point in gel card testing to allow analysis. Titration against red cells of the specified phenotype provided by the participating laboratory did not appear to introduce additional variance. Overall, results reported based on the gel card technique at the AHG phase (1+ end-point) showed reduced variance compared to tube-based techniques.

Conclusions.—A detailed, uniform method for antibody titration at 37°C and read at the AHG phase in a tube-based method with a w+ end-point reduced interlaboratory variability.

Laboratory assays for predicting the severity of haemolytic disease of the fetus and newborn

Haemolytic disease of the fetus and newborn (HDFN) is characterised by the presence of IgG antibodies in the maternal circulation which cause haemolysis in the fetus by crossing the placenta and sensitising red cells for destruction by macrophages in the fetal spleen. Serological, quantitative and cellular assays have all been developed to predict the severity of HDFN. These assays measure and/or characterise alloantibodies in the maternal circulation. Quantitative assays which accurately measure antibody levels correlate with disease severity better than serological assays which are inherently less precise. Nevertheless, high antibody levels are found in some cases of mild HFDN and relatively low antibody levels are found in some severe cases. This suggests that disease severity is influenced by factors in addition to antibody concentration. These factors remain to be fully elucidated but may include: the subclass and glycosylation of maternal antibodies; the structure, site density, maturational development and tissue distribution of blood group antigens; the efficiency of IgG transport to the fetus; the functional maturity of the fetal spleen; polymorphisms which affect Fc receptor function; and the presence of HLA-related inhibitory antibodies. Cellular assays which are sensitive to factors affecting antibody function have, therefore, been developed in an attempt to improve the prediction of disease severity. Although these assays are cumbersome, there are now sufficient data to suggest that some cellular assays provide clinically useful information to complement serological and quantitative assays.

Policies and procedures related to weak D phenotype testing and Rh immune globulin administration. Results from supplementary questions to the Comprehensive Transfusion Medicine Survey of the College of American Pathologists

OBJECTIVE

To determine and evaluate policies and procedures related to weak D phenotype testing and terminology and the administration of Rh immune globulin in selected clinical situations. Design, Setting, and Participants.-Institutions participating in the College of American Pathologists 1999 J-A Comprehensive Transfusion Medicine Survey program were asked to respond to a series of supplementary questions related to weak D phenotype testing and Rh immune globulin administration. More than 3500 institutions and transfusion services participated.

RESULTS

Most supplementary questions elicited more than 3000 responses. Despite no clinical or regulatory mandate, 58. 2% of transfusion services routinely perform an antiglobulin test for the weak D phenotype in patients who test negative with anti-D reagents. Significant differences were found concerning the transfusion of blood components to patients with the weak D phenotype and the administration of Rh immune globulin to these individuals. At least one patient with the weak D phenotype with anti-D alloantibody formation was observed during a 12-month period by 31.8% of transfusion services.

CONCLUSIONS

Significant variability concerning policies and procedures related to weak D typing and terminology was found in this survey. Transfusion of blood components to patients with the weak D phenotype and the administration of Rh immune globulin also demonstrated variations. Anti-D alloantibody formation by patients with the weak D phenotype may not be as rare as previously thought. Additional study related to the clinical significance of these results is warranted.

Transfusion Medicine: An Overview and Update

The discovery of AIDS in the 1980s and its rapid evolution as a major concern for physicians and their patients have led to many questions about the safety of the blood supply. The attention placed on AIDS has led to new discoveries and technologies to reduce the risk of other transfusion complications such as hepatitis, bacterial contamination, and transfusion-associated graft-vs-host disease. Concerns about blood safety have focused much attention on alternative blood transfusion strategies such as autologous blood, viral inactivation, and artificial blood substitutes. This review describes the transfusion medicine delivery system in the United States, with special emphasis on evolving developments and their implications for the discipline of chemical pathology.

A comparison of in vitro tests for predicting the severity of haemolytic disease of the fetus and newborn

Haemolytic disease of the newborn (HDN) is characterized by the presence of IgG antibodies in the maternal circulation which cause haemolysis in the fetus by crossing the placenta and sensitizing red cells for destruction by macrophages in the fetal spleen. Numerous serological, quantitative and cellular assays have been developed to predict the severity of HDN. These assays all measure and/or characterize alloantibodies in the maternal circulation. Quantitative assays which accurately measure antibody levels correlate with disease severity better than serological assays which are inherently less precise. Nevertheless, high antibody levels are found in some cases of mild HDN and relatively low antibody levels are found in some severe cases. This suggests that disease severity is influenced by factors in addition to antibody concentration. These factors remain to be fully elucidated but may include the subclass and glycosylation of maternal antibodies, the structure, site density, maturational development and tissue distribution of blood group antigens, the efficiency of IgG transport to the fetus, the functional maturity of the fetal spleen, polymorphisms which affect Fc receptor function, and the presence of HLA-related inhibitory antibodies. Cellular assays which are sensitive to factors affecting antibody function have therefore been developed in an attempt to improve the prediction of disease severity. Although these assays are cumbersome, there are now sufficient data to suggest that some cellular assays, when used as part of a structured approach to diagnostic testing, may provide clinically-useful information to complement serological and quantitative assays.

Application of the gel test in IgG subclassing--a comparison of two agglutination assays

BACKGROUND AND OBJECTIVES

IgG subclasses of anti-D seem to play some role in hemolytic disease of the newborn, but there has been disagreement as to its exact nature. The aim of our study was to evaluate a new technique for IgG subclassing of anti-D and to compare it to an established test.

MATERIALS AND METHODS

In 31 cases of RhD immunization, we have compared two simple agglutinating assays for subclassing anti-D: an established V-well microtiter tray assay and a new gel test assay. Polyclonal rabbit anti-IgG agglutinating antibodies were tested against sensitized D-positive red blood cells by both assays.

RESULTS

The anti-D concentration in tested sera varied between 0.1 and 81 micrograms/ml (0.5-405 IU/ml). Both assays were simple to perform and the results correlated well.

CONCLUSIONS

The gel test had two advantages: quick performance and easy interpretation.

Red cell antibodies in pregnancy: there is no 'critical titre'

The purpose of this study was to determine the predictive value and reliability of using a 'critical titre' when assessing the ability of red cell alloantibodies to cause haemolytic disease of the newborn. Titration studies and clinical follow-up of 418 antenatal cases where the mothers had red cell antibodies were studied retrospectively. The antibody specificities were anti-D (n = 359), anti-c (n = 34), anti-E (n = 19) and anti-K (n = 6). Depending on the titre being lower or higher than 16 in the indirect antiglobulin test, the severity of disease was established on the given therapy. Anti-D antibodies with a titre 16 were present in 20% of all cases associated with transfusion need of the child; for anti-c, -E and -K the figure was 4%. Titres > or = 16 resulted in both groups in 50% of the cases in phototherapy only, or no therapy at all. Titres are therefore not reliable indicators for predicting the severity of haemolytic disease of the newborn. Neither should they be used as a guide to whether or not antenatal intervention is indicated. Alternative quantitative or functional assays that measure cytotoxic lysis or phagocytosis or a combination of both should be performed instead.

Prevalence and lack of clinical significance of blood group incompatibility in mothers with blood type A or B

PURPOSE

To examine the prevalence and clinical significance of blood group incompatibility in infants whose mothers have blood type A or B.

METHODS

We prospectively analyzed cord blood samples from 4996 consecutive love-born infants for blood type, hematocrit, and results of direct antiglobulin (Coombs) test (DAT) and indirect Coombs test (ICT).

OUTCOME MEASURES

Erythrocyte sensitization was determined by positive DAT or ICT results. Significant hyperbilirubinemia (> or = 224 mumol/L (12.8 mg/dl) and mean cord hematocrits were compared between mother-infant pairs with ABO incompatibility and positive DAT or ICT results and those with negative Coombs test results.

RESULTS

Of all births, 6.9% (343/4996) were of infants who had ABO incompatibility and had been born to mothers with blood type B or A; 44 (13%) of 343 infants had a positive antiglobulin test result, of whom 43 had a positive ICT result only. Type A or B mothers were 5.5 times less likely to have sensitization than type O mothers; A-B, B-A, A-AB, and B-AB mother-infant pairs with a positive antiglobulin test result had mean cord hematocrits and rates of significant hyperbilirubinemia similar to those of corresponding pairs whose antiglobulin tests both showed negative results. Infants with a positive DAT result had lower mean cord hematocrits than infants with negative results on both antiglobulin tests or on a positive ICT result only. Significant hyperbilirubinemia was more frequent in infants with a positive DAT result than in infants with negative results on both antiglobulin tests or a positive ICT result only.

CONCLUSION

Sensitization is much rare when the mother has blood type A or B than when she has blood type O, as demonstrated by the antiglobulin test. The incidence of significant hyperbilirubinemia and lower cord hematocrit is not increased by sensitization when the mother has type A or B.

Causes and clinical consequences of Rhesus (D) haemolytic disease of the newborn: a study of a Scottish population, 1985-1990

OBJECTIVE

To identify the reasons behind failures to prevent the development of Rhesus (D) haemolytic disease of the newborn.

DESIGN

Retrospective analysis of the case records of all pregnancies that resulted in the birth of an infant with a positive direct antiglobulin test on the cord red cells born to Rh(D) negative women between 1 April 1985 and 31 March 1990.

SETTING

Obstetric units in the South East Scotland region and the South East Scotland Regional Blood Transfusion Service Antenatal Laboratory.

MAIN OUTCOME MEASURES

The causes and clinical consequences of maternal immunisation to the Rhesus (D) antigen.

RESULTS

Between 1985 and 1990, 80 pregnancies resulted in the birth of an infant sensitised with anti-D on the cord red cells. There were no deaths due to haemolytic disease, but considerable resources were deployed in obstetric and neonatal care for these pregnancies. Sufficient data were available to categorise the cause of maternal immunisation in 70 pregnancies. Seven cases were due to immunisation by pregnancy before 1970. Sixty-three cases could be attributed to failure of the Rhesus programme: 10 cases (16%) were due to failure to implement the programme adequately, the other 53 cases (84%) were due to failure of the current guidelines to provide adequate protection. Late immunisation in an uncomplicated pregnancy was the single commonest identifiable cause.

CONCLUSIONS

It is likely that substantial further reductions in Rhesus (D) immunisation and haemolytic disease of the newborn will require changes in the Rhesus prevention programme. In particular the role of antenatal prophylaxis requires detailed consideration.

Alloimmunisation via previous transfusion places female Kpb-negative recipients at risk for having children with clinically significant hemolytic disease of the newborn

We report a case of clinically significant hemolytic disease of the newborn due to Kpb alloimmunisation requiring obstetric intervention. This case and a review of the literature are in contrast to reviews of hemolytic disease of the newborn that either ascribe no significance to the Kpb antigen or suggest that it causes only rare or mild disease. Analysis of our Kpb-negative donor pool suggests that prior transfusion greatly increases the chance of alloimmunisation. The role of frozen rare donor registry cells as a public resource is emphasised.