Laboratory measurement of fetomaternal hemorrhage and its clinical relevance

Application of flow cytometry in transfusion medicine: The Sanjay Gandhi Post Graduate Institute of Medical Sciences, India experience

The application of flow cytometry (FC) is diverse and this powerful tool in used in multiple disciplines such as molecular biology, immunology, cancer biology, virology, and infectious disease screening. FC analyzes a single cell or a particle very rapidly as they flow past single or multiple lasers while suspended in buffered solution. FC has a great impact in the field of transfusion medicine (TM) due to its ability to analyze individual cell population and cell epitopes by sensitive, reproducible, and objective methodologies. The main uses of FC in TM are detection of fetomaternal hemorrhage, diagnosis of paroxysmal nocturnal hemoglobinuria, quantification of D antigen, detection of platelet antibody, quality control of blood components, for example, residual leukocyte counts and evaluation of CD34-positive hematopoietic progenitor cells in stem cell grafts. In recent years, FC has been implemented as an alternative method for the detection and characterization of red cell autoantibodies in autoimmune hemolytic anemia. Many workers considered FC as a very good complement when aberrant expression of various erythrocyte antigens needs to be elucidated. It has been extensively used in the resolution of ABO discrepancies and chimerism study. FC has also been used successfully in various platelet immunological studies. In the recent past, FC has been used in several studies to assess the platelet storage lesions and elucidate granulocyte/monocyte integrity and immunology. FC analysis of CD34+ stem cells is now the method of choice to determine the dosage of the collected progenitor cells. The technique is vastly used to evaluate residual leukocytes in leukodepleted blood components. We conclude that flow cytometers are becoming smaller, cheaper, and more user-friendly and are available in many routine laboratories. FC represents a highly innovative technique for many common diagnostic and scientific fields in TM. Finally, it is the tool of choice to develop and optimize new cellular and immunotherapeutic trials.

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.

Pathology Consultation on Patients With a Large Rh Immune Globulin Dose Requirement

OBJECTIVES

To review the differential diagnosis and laboratory issues for women with a large calculated dose of Rh immune globulin (RhIG).

METHODS

A case-based approach is used to review the differential diagnosis of patients with a large calculated dose of RhIG, RhIG dosing for women with baseline elevations in hemoglobin F, the formulations of RhIG, and issues for the transfusion medicine service with the release of large doses of RhIG.

RESULTS

A large fetomaternal bleed after delivery requiring multiple doses of RhIG is rare. Such patients may require intravenous RhIG to avoid multiple injections. Patients with a large percentage of circulating fetal RBCs should be evaluated for a disorder of hemoglobin synthesis and, if present, should have quantification of the circulating fetal RBCs by flow cytometry.

CONCLUSIONS

Accurate laboratory evaluation of women with large fetomaternal bleeds is essential for appropriate RhIG administration.

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.

Semiautomated data analysis of flow cytometric estimation of fetomaternal hemorrhage in D- women

BACKGROUND

Accurate and reliable measurement of the volume of fetal D+ cells in D- women is required for adequate anti-D prophylaxis. A semiautomated flow cytometry assay based on a standardized calibration curve that was created with simulated fetomatemal hemorrhage (FMH) mixtures was developed.

STUDY DESIGN AND METHODS

A calibration range of 0.083- to 2-percent D+ cells in the D-RBC mixtures (2-44 mL calculated FMH) was analyzed by use of a flow cytometer (XL-MCL, Coulter Electronics Ltd). Linear regression analysis of the calibration curve data with computer software (Excel, Microsoft) allowed semiautomated determination of the FMH volume. To optimize the assay, fresh versus frozen and thawed RBCs, RBCs from adults who are heterozygous for D or cord RBCs, and indirect- or direct-labeling techniques were evaluated by use of MoAbs.

RESULTS

Fresh RBCs from adults heterozygous for D were chosen for routine use, although equivalent calibration curves were obtained with all cells tested (n = 12 calibration assays; r2 = 0.999; mean SD, 14%). A monoclonal anti-D reagent (Therad 10, Diagnostics Scotland) worked well in both indirect-(anti-IgG F(ab)-FITC) and direct-(anti-D-FITC) labeling methods compared to the use of BRAD-3 FITC. In routine practice, the FMH volumes obtained were mainly lower than those obtained in the Kleihauer Betke test when there was less than 4 mL of FMH.

CONCLUSION

Semiautomated data acquisition and calibration curve analysis represents a further step toward standardization of flow cytometry for accurate FMH quantification and facilitates evaluation and control of day-to-day variations between laboratories, flow cytometers, and operators.

Quantification of foetomaternal haemorrhage. An analysis of two cytometric techniques and a semiquantitative gel agglutination test

Traditional tests to screen for foetomaternal haemorrhage are time-consuming and difficult to perform. The Kleihauer test is widely used but difficult to standardize. We evaluated three techniques for quantifying foetomaternal haemorrhage: a semiquantitative gel agglutination test and two flow cytometric techniques. The gel agglutination test is based on the consumption of anti-D reagent by D+ cells, analysing the reaction of the supernatant against indicator cells in a Coombs-gel card. In the two colour direct immunofluorescent technique, the sample is incubated with Per-CP labelled anti CD45 antibody, fixed with glutaraldehyde and permeabilized by exposure to Triton X-100. An aliquot is stained with an antibody to foetal haemoglobin, conjugated with fluorescein isothiocyanate or phycoerythrin. The indirect immunofluorescent technique is based on the labelling of Rh (D) antigen with an anti D reagent, followed by the addition of an anti IgG antibody conjugated with phycoerythrin. Foetomaternal haemorrhage was not detected in 75 of the 85 samples analysed by the direct immunofluorescent technique. In the remaining 10 samples, the volume was very low. Thirty-five samples with Rh (D) antigen incompatibility were analysed in parallel by the indirect immunofluorescent technique and in 15 of the 35 samples, the gel agglutination technique was also carried out. The three techniques gave similar results. The gel agglutination test can be used to screen for foetomaternal haemorrhage, while greater volumes should be quantified by flow cytometric techniques.