The Kleihauer technique: an accurate method of quantifying fetomaternal haemorrhage?

HPLC and flow cytometry combined approach for HbF analysis in fetomaternal haemorrhage evaluation

Introduction

Recently, a flow cytometric (FC) based test has been developed for detection of circulating fetal cells to replace the less accurate and reproducible Kleihauer-Betke test.FC test is easier to perform, it can distinguish the origin of fetal cells, but it is expensive and available in highly specialized laboratories. We evaluated the introduction of high-performance liquid chromatography (HPLC) approach as initial screening to identify patients who need an additional FC test to better discriminate the nature of haemoglobin-F (HbF) positive cells.

Methods

Blood samples from 130 pregnant women suspected to have fetomaternal haemorrhage were analysed with HPLC and FC methods. The cut-off for HbF HPLC concentration was calculated. Statistical analyses for the evaluation of HPLC as a screening method were performed. The positivity cut-off of HbF to be used as decision-making value to continue the investigation was calculated.

Results

An excellent agreement (R2 > 0.90) was observed between the percentage of HbF obtained by HPLC and the percentage of fetal cells detected by FC. Results obtained from each assay were compared to define the HPLC threshold below which it is not necessary to continue the investigations, confirming the maternal nature of the HbF positive cells detected. Our study demonstrated that a cut-off of 1.0 % HbF obtained by HPLC was associated with the lowest rate of false negative results in our patient cohort.

Conclusions

This study provides a new FMH investigation approach that possibly leads to a reduction in times and costs of the analysis.

Evaluation of machine learning-driven automated Kleihauer-Betke counting: A method comparison study

INTRODUCTION

The Kleihauer-Betke (KB) test is the diagnostic standard for the quantification of fetomaternal hemorrhage (FMH). Manual analysis of KB slides suffers from inter-observer and inter-laboratory variability and low efficiency. Flow cytometry provides accurate quantification of FMH with high efficiency but is not available in all hospitals or at all times. We have developed an automated KB counting system that uses machine learning to identify and distinguish fetal and maternal red blood cells (RBCs). In this study, we aimed to evaluate and compare the accuracy, precision, and efficiency of the automated KB counting system with manual KB counting and flow cytometry.

METHODS

The ratio of fetal RBCs of the same blood sample was quantified by manual KB counting, automated KB counting, and flow cytometry, respectively. Forty patients were enrolled in this comparison study.

RESULTS

Comparing the automated KB counting system with flow cytometry, the mean bias in measuring the ratio of fetal RBCs was 0.0048%, with limits of agreement ranging from -0.22% to 0.23%. Using flow cytometry results as a benchmark, results of automated KB counting were more accurate than those from manual counting, with a lower mean bias and narrower limits of agreement. The precision of automated KB counting was higher than that of manual KB counting (intraclass correlation coefficient 0.996 vs 0.79). The efficiency of automated KB counting was 200 times that of manual counting by the certified technologists.

CONCLUSION

Automated KB counting provides accurate and precise FMH quantification results with high efficiency.

Enumeration of Fetal Red Blood Cells, Hemoglobin-Specific RBC Cells, and F Reticulocytes in Human Blood

Recent advances in analytical cytometry have improved diagnostic tools for the study of erythropoiesis in anemic patients and resolution of differential diagnosis in diseases of the erythron. This article presents three applications of red blood cell (RBC) analysis-quantitation of fetal red cells, F-cell enumeration, and F-reticulocyte analysis-which improve diagnostic precision, sensitivity, and specificity, and provide better laboratory indicators of therapeutic efficacy in a variety of hematologic and obstetric disorders. Such advances also include the measurement and quantitation of RBC hemoglobins and their relative ribonucleic acid levels. These advances not only promise to improve diagnostic accuracy and laboratory precision over techniques such as the traditional manual reticulocyte counting method and the Kleihauer-Betke stain method for evaluating fetomaternal hemorrhage (FMH), but also serve as tools for newer assays of anemia diagnosis and improved clinical outcomes. In addition to the primary methods, supporting techniques for preparing spiked controls, automating data analysis, setting up a fetal hemoglobin acquisition protocol, and assaying reticulocytes using thiazole orange are also presented. © 2019 by John Wiley & Sons, Inc.

Use of Fetal Hemoglobin Quantitation for Rh-Positive Pregnant Females: A National Survey and Review of the Literature

CONTEXT.—

The Kleihauer-Betke (KB) test is validated for estimating the dose of Rh immune globulin needed for Rh-negative pregnant females. However, some clinicians are also ordering the test for Rh-positive women. The degree to which this practice occurs is unknown.

OBJECTIVE.—

To evaluate the number of laboratories that perform the KB test on Rh-positive pregnant women, and to establish current ordering practices for this indication.

DESIGN.—

We added 9 supplemental questions regarding KB test use for fetomaternal hemorrhage to the 2016 College of American Pathologists proficiency test survey. We also reviewed the available literature regarding the diagnostic utility of the KB test for Rh-positive women.

RESULTS.—

A total of 1578 surveys were evaluated and revealed that 52% (824) of respondents perform these tests for Rh-positive women, and more than 50% (440 of 819; 53.7%) of these laboratories report that the results for Rh-positive women are treated as important or very important.

CONCLUSIONS.—

The KB test is commonly used for Rh-positive women, and the information obtained from the test is considered as urgent and important. However, the available literature in support of this practice is still nonconclusive.

[Trauma and pregnancy: Is the Kleihauer-Betke test really useful?]

OBJECTIVE

To evaluate the pertinence of Kleihauer-Betke (KB) test, in case of abdominal trauma during pregnancy in forecast of fetal outcomes, according to trauma severity.

METHODS

A single-center retrospective study conducted between January 2014 and April 2016 in a maternity type III and a trauma center, which included the pregnant women admitted for abdominal trauma. The trauma's severity was assessed using the guidelines of the Society of Obstetricians and Gynaecologists of Canada. The impact of a positive KB test, defined as>0.1%, was analyzed. Adverse outcome was defined as one or more of the following complications: intrauterine fetal death, placental abruption, pre-term birth<37 weeks of gestation, and fetal or neonatal anemia.

RESULTS

During the study period, 265 pregnancies involved into an abdominal trauma were included: 69% with a minor trauma and 31% with a severe trauma. Of all patients, 5.6% presented a positive KB test, among then 15.4% had an adverse outcome. There was no significant difference in the rate of adverse outcomes in the positive KB group and the KB negative group either in the overall population (P=0.16), in the minor trauma population (P=1) or in the major trauma population (P=0.14). The predictive positive values were respectively in the global population, in the minor trauma group and in the severe trauma group 15.4%, 0% and 25%.

CONCLUSIONS

The KB test does not seem to be useful in case of trauma during pregnancy to define adverse outcome.

Flow Cytometry in Detection of Fetal Red Blood Cells and Maternal F Cells to Identify Fetomaternal Hemorrhage

Accurate detection and quantitation of fetomaternal hemorrhage (FMH) is critical to the obstetric management of rhesus D alloimmunization in Rh-negative pregnant women. The flow cytometry is based on the detection of fetal red blood cells using a monoclonal anti-HbF antibody, and is the method most indicated for this estimation. The objective of this study was to quantify fetal red blood cell levels of pregnant women using flow cytometry. We analyzed 101 peripheral blood samples from Rh-negative and Rh-positive women, whose mean age was 24 years (20-32 years), after vaginal delivery or cesarean section. Our study showed that 53% of pregnant women had fetal red blood cells levels <2.0 mL, 31% between 2.0-3.9 mL, 16% between 4.0-15.0 mL, and 1% >15.0 mL. Accurate quantitation of fetal red blood cells is necessary to determine the appropriate dose of anti-D (RHD) immunoglobulin to be administered to pregnant or postpartum women.

Fetomaternal Hemorrhage following Placement of an Intrauterine Pressure Catheter: Report of a New Association

Fetomaternal hemorrhage (FMH) can be associated with significant perinatal mortality. Our review of the literature did not identify any cases of FMH following placement of an intrauterine pressure catheter (IUPC). In our case, an IUPC was inserted in a patient undergoing induction of labor at term. Fetal bradycardia ensued shortly after placement, warranting an emergent cesarean delivery. Severe neonatal anemia was identified, and evaluation of maternal blood was consistent with massive FMH. This is the first reported association between FMH and IUPC placement. If this relationship is validated in future reports, appropriate changes in clinical practice may be warranted.

Acute and chronic fetal anemia as a result of fetomaternal hemorrhage

Introduction. Fetomaternal hemorrhage represents a transfer of fetal blood to the maternal circulation. Although many etiologies have been described, most causes of fetomaternal hemorrhage remain unidentified. The differentiation between acute and chronic fetomaternal hemorrhage may be accomplished antenatally and may influence perinatal management. Case. A 36-year-old gravida 6 para 3 presented at 37 and 5/7 completed gestational weeks with ultrasound findings suggestive of chronic fetal anemia such as right ventricular enlargement, diminished cerebral vascular resistance, and elevated middle cerebral artery end-diastolic velocity. On the other hand, signs of acute fetal decompensation such as deterioration of the fetal heart tracing, diminished biophysical score, decreased cord pH, and increased cord base deficit were noted. Following delivery, the neonate's initial hemoglobin was 4.0 g/dL and the maternal KB ratio was 0.015 indicative of a significant fetomaternal hemorrhage. Discussion. One should consider FMH as part of the differential diagnosis for fetal or immediate neonatal anemia. We describe a unique case of FMH that demonstrated both acute and chronic clinical features. It is our hope that this case will assist practitioners in differentiating acute FMH that may require emergent delivery from chronic FMH which may be able to be expectantly managed.

Reference values of fetal erythrocytes in maternal blood during pregnancy established using flow cytometry

The aim of our study was to assess the fetal RBC count in maternal blood during uncomplicated pregnancies from 26 weeks onward. We used a flow cytometric method specifically designed for use in a routine hematology analyzer. Pregnant women were recruited through midwives. The participating laboratories used the FMH QuikQuant method (Trillium Diagnostics, Brewer, ME) in a CELL-DYN Sapphire hematology analyzer (Abbott Diagnostics, Santa Clara, CA). The method is based on a monoclonal antibody to hemoglobin F. Flow cytometric data were analyzed by 2 independent observers. The 95th percentile reference range was estimated according to Clinical and Laboratory Standards Institute guidelines. A total of 236 samples were statistically analyzed. Gestational ages ranged from 21.6 to 41 weeks (mean, 32.0 weeks), and the fetal RBC count in maternal blood ranged from 0.00% to 0.50% (median, 0.025%). The fetal RBC count in maternal blood shows no correlation with gestational age. The established reference range during normal pregnancy is less than 0.125%.

Flowcytometric assessment of fetomaternal hemorrhage during external cephalic version at term

External cephalic version (ECV) at term is a safe procedure and reduces the incidence of cesarean sections for breech presentation. One of the known complications, however, is an ECV-related disruption of the placental barrier and a subsequent transfusion of fetal blood into maternal circulation. While the incidence of ECV-related fetomaternal hemorrhage (FMH) has been determined recently in a large trial using a manual Kleihauer-Betke test (KBT), questions remain on the amount of ECV-related FMH. KBT, which detects fetal red blood cells (RBC) on the basis of acidic resistance of fetal hemoglobin (HbF), is known to be a sensitive test, yet prone to procedural errors limiting its accuracy in quantifying FMH. In this study we investigated 50 patients for FMH before and after ECV, using a dual-color flow cytometric test kit with a lower limit of quantification of 0.05% fetal RBC in maternal peripheral blood. Three patients had a quantifiable increase of fetal RBC detected after ECV (0.06%; 0.08%; 0.1%). None of these subtle increments was predictable by ECV-related clinical parameters or translated into fetal compromise. Using a sensitive and accurate flow cytometric test method, our data provide further assurance to mothers on the safety of ECV at term.

Flow cytometric assessment of feto-maternal hemorrhage; a comparison with Betke-Kleihauer

OBJECTIVES

Assessing the number of fetal cells in the maternal circulation quantifies the volume of feto-maternal hemorrhage, enhancing the ability to provide effective prevention of Rhesus (Rh) allommunization and appropriate fetal surveillance in cases of significant feto-maternal hemorrhage.

METHODS

Having developed a standard curve with maternal samples spiked with known volumes of fetal red blood cells, we used a flow cytometric method using fluorescent labeled antihemoglobin F to quantitate fetal cells in the maternal circulatory system in two groups of women undergoing chorionic villus sampling (CVS), by either biopsy forceps or cannula aspiration (n = 170 women). We compared these results with the gold standard, the Betke-Kleihauer test.

RESULTS

Our results show good correlation between the flow cytometric method and the traditional Betke-Kleihauer method for fetal red cell quantitation (r(2) = 0.99). Fetal red blood cells were identified in 10 women by the Betke-Kleihauer method, and in 26 women by flow cytometry. CVS was not associated with an increase in feto-maternal hemorrhage.

CONCLUSION

Flow cytometry was both more sensitive and more timely for the quantitation of feto-maternal hemorrhage than was Betke-Kleihauer.

Assessment of Fetomaternal Hemorrhage by Flow Cytometry and Kleihauer-Betke Test in Rh-Negative Pregnancies

OBJECTIVES

To assess the efficacy of flow cytometry (FC) in the detection and quantification of fetomaternal hemorrhage (FMH) in comparison to the Kleihauer-Betke test (KBT).

METHODS

25 unsensitized Rh-negative mothers who had delivered Rh-positive infants were included. Presence of FMH was determined by KBT and FC using FITC-labeled BRAD-3 antibodies.

RESULTS

FMH was detected in 19 (76%) patients by FC and 23 (92%) patients by KBT prior to delivery, and in 21 (84%) patients by FC and 23 (92%) patients by KBT after delivery. The mean volume of FMH in the post-delivery samples by KBT and FC were 0.34 +/- 0.26 ml (range 0.05-1.2 ml) and 0.37 +/- 0.57 ml (range 0.02-2.6 ml) respectively. The volume of post-delivery FMH estimated by KBT and FC correlated well (r = 0.75; ICC alpha = 0.73). A higher agreement between KBT and FC was seen in the 0.1-0.5 ml range (kappa = 0.65; p < 0.01).

CONCLUSIONS

Both manual KBT and FC using FITC-BRAD-3 antibodies show good sensitivity in detecting and quantifying fetal red cells. There is a good correlation between the methods in the 0.1- to 0.5-ml range of FMH.

Identification and quantification of fetal red blood cells in maternal blood by a dual-color flow cytometric method: evaluation of the Fetal Cell Count kit

BACKGROUND

As an alternative to the cumbersome Kleihauer-Betke test (KBT), flow cytometry represents a powerful method for the identification and quantification of fetal red blood cells (RBCs) in maternal circulation.

STUDY DESIGN AND METHODS

The aim of this study was to evaluate the Fetal Cell Count kit (IQ Products), an innovative flow cytometric method, based on the combination of antibodies directed, respectively, against fetal hemoglobin (HbF) and carbonic anhydrase (CA), a marker expressed after birth, to discriminate fetal RBCs from adult F cells containing HbF. The investigation was performed by two French laboratories that compared the data obtained by flow cytometry and KBT in 455 pregnant or just-delivered women as well as in 124 artificial mixtures containing from 0.01 to 5.00 percent cord cells.

RESULTS

The FL1/FL2 histogram allowed distinction between fetal RBCs (HbF+, CA-), F cells (HbF+, CA+), and adult RBCs (HbF-, CA+). The limits of detection and quantification were determined at 0.03 and 0.10 percent or 0.02 and 0.05 percent when analyzing 100,000 or 200,000 events, respectively. Linearity was demonstrated between 0.01 and 5.00 percent fetal cells in the mixtures (r = 0.95, p < 0.01). A good correlation between fluorescence-activated cell sorting (FACS) and KBT results was obtained with artificial mixtures (r = 0.94, p < 0.01). From the 405 Kleihauer-negative samples, none were identified as positive by FACS. Among the 50 Kleihauer-positive samples, 6 were shown not to contain fetal cells but F cells by FACS.

CONCLUSION

With this new dual-color flow cytometric method, accurate evaluation of fetomaternal hemorrhage was achieved even in the face of HbF of maternal origin.

Detection of fetomaternal hemorrhage following chorionic villus sampling by Kleihauer Betke test and rise in maternal serum alpha feto protein

OBJECTIVES

To assess incidence and volume of fetomaternal hemorrhage (FMH) after chorionic villus sampling (CVS) by Kleihauer Betke test (KBT) and rise in maternal protein (MSAFP).

METHODS

A prospective study was conducted on 61 cases requiring CVS. FMH due to CVS was assessed by KBT and MSAFP.

RESULTS

Out of 61 cases, 60 (98.36%) cases showed FMH by MSAFP while all showed FMH by KBT. Median volume of FMH detected by MSAFP was 0.06 mL (25 to 75th interquartile (IQR) 0.01 to 0.12 mL) and by KBT was 0.45 mL (25 to 75th IQR 0.09 to 0.90). Mean volume of FMH detected by MSAFP was 0.1 + 0.1424 mL and by KBT was 0.58 + 0.637 mL. Significant FMH up to 0.1 mL was found in 20 (32.8%) and 45 (60.6%) by MSAFP and KBT respectively.

CONCLUSION

MSAFP and KBT are sensitive to detect FMH. KBT estimates more FMH than MSAFP. Fifty micrograms of anti-D is sufficient to cover FMH during CVS.

Immunocytometric quantitation of foeto-maternal haemorrhage with the Abbott Cell-Dyn CD4000 haematology analyser

This study evaluated the extended use of a haematology analyser (Abbott Cell-Dyn CD4000) for the immunofluorescent enumeration of foeto-maternal haemorrhage (FMH) with fluorescein isothiocyanate-labelled monoclonal anti-RhD. Method performance was assessed with artificial FMH standards, and a series of 44 clinical samples. Within run precision was <15% (coefficient of variation, CV) for FMH volumes of 3 ml and above, 18.8% at an FMH volume of 2 ml and 31.7% at an FMH volume of 1 ml. Linearity analysis showed excellent agreement (observed FMH% = 0.98x expected FMH% + 0.02), and a close relationship (R(2) = 0.99) between observed and expected FMH percentages. The lower limit of quantification of the CD4000 (SRP-Ret) method with a maximum CV of 15% was 1.6 ml, and the limit of detection was <1 ml. Parallel Kleihauer-Betke test (KBT) assessments of FMH standards showed an overall trend for higher KBT values (observed = 1.25x expected - 0.38). At an FMH level of 4 ml, KBT observer estimates ranged from 0.57 to 11.94 ml with a mean inter-observer CV of 63%. For 44 clinical samples, there was decision point agreement between KBT and SRP-Ret results for 42 samples with an FMH of <2 ml. Analysis in the low FMH range (<1 ml) showed that small volume foetal leaks could be detected with the SRP-Ret method in most of 23 samples with negative KBT results. CD4000 SRP-Ret method performance for FMH determination was similar to that reported for flow cytometry.

Risk factors for fetal-to-maternal transfusion in Rh D-negative women--results of a prospective study on 942 pregnant women

AIMS

To investigate the incidence of severe fetal-to-maternal transfusion after delivery and to identify risk factors.

MATERIAL AND METHODS

In a prospective study at the Department of Obstetrics, Charité, Campus Virchow-Klinikum, Berlin, Germany, we analyzed the incidence of severe fetal-to-maternal transfusion (>10 ml) and fetal-to-maternal hemorrhage (>25 ml) in Rh D-negative pregnant women after delivery of Rh D-positive infants. 942 women were included in the study and Kleihauer-Betke tests were performed. The results were compared to perinatal data.

RESULTS

Fetal-to-maternal hemorrhage occurred in 13 cases out of 942 (incidence of 1.3%) and severe fetal-to-maternal transfusion in 61 cases (6.5%). In all of the cases with fetal-to-maternal hemorrhage, mothers were compatible with their infants in ABO-system. The incidence of fetal-to-maternal transfusion and its severe form was significantly higher in twin pregnancies (7/21 cases and 5/21 cases respectively, 33.3% and 23.8%) than in singleton pregnancies (22.5%, and 5.9%, P<0.001). All other factors, such as maternal age, parity, ethnicity, mode of delivery, presentation, duration of first and second stage of labor, CTG, or Apgar score were not associated with an increased risk of severe fetal-to-maternal transfusion.

CONCLUSIONS

Twin pregnancy is the only independent risk factor for severe fetal-to-maternal transfusion. ABO-incompatibility between mother and infant seems to be protective against Rh D-alloimmunization.

Quantification of fetomaternal hemorrhage: a comparative study of the manual and automated microscopic Kleihauer-Betke tests and flow cytometry in clinical samples

OBJECTIVE

The purpose of this study was to evaluate the quantification of fetomaternal hemorrhage by the manual and automated microscopic analysis of Kleihauer-Betke stained slides and by flow cytometry.

STUDY DESIGN

Blood smears were stained and evaluated manually according to the Kleihauer-Betke test. The same slides were used for automated microscopy. In addition, blood flow cytometry was performed by anti-hemaglobin F immunostaining.

RESULTS

Fetomaternal hemorrhage >0.1% was detected in 4 patients by manual and automated Kleihauer-Betke test and by blood flow cytometry. Fetomaternal hemorrhage was absent according to all 3 methods in 13 patients; fetomaternal hemorrhage<0.1% was detected in 27 patients by either manual or automated Kleihauer-Betke test or both. Moderate agreement was observed between the manual and automated Kleihauer-Betke test (weighted kappa, 0.56; 95% CI, 0.33-0.78). Agreement between the manual Kleihauer-Betke test and blood flow cytometry was fair (weighted kappa, 0.40; 95% CI, 0.15-0.66).

CONCLUSION

Automated microscopic detection of fetal blood cells in clinical samples provides accurate quantification that is comparable to the manual Kleihauer-Betke test in both small and large fetomaternal hemorrhage. Blood flow cytometry is capable only of quantifying fetomaternal hemorrhage of >0.1%.

Cell-free fetal DNA levels in maternal plasma after elective first-trimester termination of pregnancy

OBJECTIVE

To determine if first-trimester elective termination of pregnancy affects cell-free fetal DNA (fDNA) levels in maternal plasma.

DESIGN

Prospective cohort study.

SETTING

Clinical and academic research centers.

PATIENT(S)

One hundred thirty-four women who underwent first-trimester elective termination procedures.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Real-time polymerase chain reaction (PCR) amplification and measurement of DYS1, a Y-chromosome sequence, was used as a marker of fDNA.

RESULT(S)

We detected fDNA in pretermination samples from 27 out of 71 patients in the surgical arm, and 29 out of 63 patients in the medical arm. Based on confirmation of male gender in placental tissue, the sensitivity of fDNA detection is 92.6%. We detected fDNA as early as 32 days of gestation, which increased 4.2 genome equivalents/mL/week. In the surgical arm, the mean level of posttermination fDNA, adjusted for the clearance of fDNA in maternal blood, was higher than projected based on an expected increase with gestational age. In the medical arm, six patients had increased fDNA levels up to 11 days following termination.

CONCLUSION(S)

We found that fDNA can be reliably quantified in the early first trimester; fDNA elevation that occurs shortly after surgical termination may reflect fetomaternal hemorrhage or destruction of trophoblastic villi. Continued elevation of fDNA for several days may occur following medical termination.

Improvement of the Kleihauer-Betke test by automated detection of fetal erythrocytes in maternal blood

BACKGROUND

Reliable detection and quantification of fetal red cells in maternal blood is important in routine obstetric practice. The manual Kleihauer-Betke test (KBT) is widely used, but it is imprecise and subjective. This study investigated whether automated readout of the KBT could improve sensitivity and accuracy.

METHODS

Glass slides containing dilutions of fetal red cells in adult blood were prepared and stained by using acid elution. Standard manual evaluation of the KBT was performed for all slides by one investigator. In addition, automated microscopy and image analysis of the same slides were performed, whereby detected fetal cells were reviewed by two independent investigators.

RESULTS

Ten replicate measurements of fetal cell numbers showed high reproducibility and very small interobserver and intraobserver variabilities. Typical coefficients of variation were 3-4% for concentrations ranging from 0.001% to 0.1%. The automated KBT showed strong correlation between theoretical and detected concentrations of fetal cells (r2 = 0.999). In the range from 0.0001% to 0.001%, the standard KBT underestimated the fetal cell percentage, whereas the automated KBT was very precise. The correlation between methods was good (r2 = 0.999).

CONCLUSION

Automated readout of the KBT improved accuracy of fetal cell detection in the range from 0.0001% to 1% fetomaternal hemorrhage, particularly when larger numbers of cells were analyzed.

Testing for hematologic disorders and complications

This review summarizes state-of-the-art and emerging techniques in the antenatal diagnosis of fetal anemia and hemoglobinopathies. Fetal anemia may result from hemolytic disease, hemorrhage, suppression of erythropoiesis, infection (eg, parvovirus B19), or trauma. The clinical laboratory plays an essential role in the evaluation of these disorders by way of the use of various hematologic, biochemical, serologic, cytometric, and molecular genetics methods. Hemoglobinopathies are the most common class of single gene disorders worldwide. The authors have used the example of homozygous alpha-thalassemia major (Hb Barts disease) as a paradigmatic case for antenatal hemoglobinopathy screening. Perhaps the most familiar indication for hematologic screening in pregnancy is HDFN, most commonly in pregnancies previously sensitized to the RhD antigen. All pregnant women, regardless of their past medical or obstetric history or previous antibody screens, should have ABO/Rh blood typing and a red cell antibody screen performed at the first prenatal visit. Long-established methods for assaying FMH (KB method), microcytosis (hemogram with red cell indices), and blood group incompatibility (direct antigen test, serologies) remain critical for rapid, sensitive diagnosis. Analysis of fetal free DNA in maternal plasma holds the promise for rapid, ultrasensitive, and noninvasive detection of many fetal hematologic disorders.

Quantification of fetomaternal hemorrhage by fluorescence microscopy is equivalent to flow cytometry

BACKGROUND

The quantification of fetal cells in the maternal circulation remains an important goal to determine the amount of anti-D necessary to prevent active immunization of a D- mother giving birth to a D+ baby. Underestimation of fetomaternal hemorrhage (FMH) results in inefficient anti-D prophylaxis and maternal immunization; overestimation of FMH results in higher doses of passively transferred anti-D, higher costs, and the risk of disease transmission. Thus, a reliable method to quantitatively assess FMH is necessary.

STUDY DESIGN AND METHODS

Serial dilutions of artificial FMH were quantitatively measured by three different methods: flow cytometry, fluorescence microscopy (each after anti-D staining), and by the Kleihauer-Betke test. The accuracy and precision of the three methods were compared by statistical analysis.

RESULTS

Fluorescence microscopy and flow cytometry were comparably accurate and precise in quantifying FMH. In contrast, the accuracy of the Kleihauer-Betke test was poor, resulting in substantial overestimation of FMH in the samples with lower fetal cell concentrations.

CONCLUSION

Anti-D flow cytometry and fluorescence microscopy for detection of fetal cells offer equally reliable and precise methods in contrast to the Kleihauer-Betke test. Fluorescence microscopy may be established as standard to quantify FMH in clinical practice because it is comparable to flow cytometry; in addition, it is time saving and is less expensive.

Diagnostic advances in defining erythropoietic abnormalities and red blood cell diseases

The majority of clinical applications of flow cytometry begin with various approaches to remove red blood cells (RBCs) from the clinical sample. However, multiparameter cytometry has and will continue to contribute much to the understanding of the pathophysiology and diagnostic accuracy in the clinical evaluation of human diseases affecting erythroid cells. This review summarizes the diagnostic advances relating to erythroid cells in the areas of immunohematology, laboratory hematology, and infectious disease with particular emphasis on medical evaluation of the anemic patient and fetomaternal hemorrhage. Semin Hematol 38:148-159.