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

A novel laboratory technique demonstrating the influences of RHD zygosity and the RhCcEe phenotype on erythrocyte D antigen expression

D antigen is the most immunogenic and clinically relevant antigen within the complex Rh blood group system. Variability of D antigen expression was first described decades ago but has rarely been investigated quantitatively, particularly in the context of RHD zygosity along with RhCcEe serological phenotype. With IRB approval, 107 deidentified blood samples were analyzed. Rh phenotypes were determined serologically by saline technique using monoclonal antibodies against D, C, c, E, and e antigens. RHD zygosity was determined using both PCR-restriction fragment length polymorphisms and quantitative real-time PCR techniques. A novel and robust method was developed for quantitation of erythrocyte D antigen sites using calibrated microspheres and flow cytometry, allowing correlation of D antigen density with RHD zygosity and expression of Rh CcEe antigens. Subjects homozygous for RHD expressed nearly twice the number of D antigen sites compared with RHD hemizygotes (33,560 ± 8,222 for DD versus 17,720 ± 4,471 for Dd, P < 0.0001). Expression of c or E antigens was associated with significantly increased erythrocyte D antigen expression, whereas presence of C or e antigens reduced expression. These data and this novel quantitation method will be important for future studies investigating the clinical relevance of D antigen variability.

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.

The issue of anti-D: an integrated seamless approach from recognition of need to bedside administration

BACKGROUND

The appropriate and timely administration of Anti-D immunoglobulin to Rhesus (D) negative women who have delivered Rhesus (D) positive babies is a vital part of obstetric care. Anti-D has an especially high profile in Ireland because of the tragic inadvertent transmission of Hepatitis C to Irish women in past decades.

AUDIT

We have reviewed our policy and procedures pertaining to the administration of Anti-D for sensitising events during pregnancy and postnatally, in the Mid-Western Health Board in 1999/2000. As a result, major changes were made in the storage, issue, recording and administration of Anti-D. New procedures in the transfusion laboratory and in the maternity hospital have been accepted by scientists and midwives and supported by haematology and obstetric medical staff. The pharmacy and haematology laboratory no longer have a role in this programme. IMPLEMENTATION OF MULTI-DISCIPLINARY CHANGE MANAGEMENT: As a result of these changes, the storage, issuing and tracking of Anti-D has become the responsibility of the hospital blood bank. Measurement offoeto-maternal haemorrhage (FMH) is now the responsibility of bio medical scientists in blood bank, utilising both flow cytometry (increasingly recognised as the gold standard method) and the Kleihauer method (Kleihauer-Betke). The programme has moved from a doctor-administered IV Anti-D Ig, to a midwife-administered IM preparation. Prescription remains the responsibility of the doctor. These changes are facilitated by the protocol guided issue of the appropriate dose of Anti-D Ig by bio medical scientists to midwives. The issue of the Anti-D Ig occurs simultaneously with issue of results of mother and baby's serology testing and estimation of volume of FMH. These major changes have been guided by audit and needs assessment and require close liaison between medical, nursing and laboratory scientific staff in haematology, transfusion and obstetrics. CRITICAL INCIDENT AUDIT-CASE REPORT: Before new procedures became official policy, a critical incident audit allowed us to pilot our protocol and to revise it using draft new procedures. In this critical incident we describe successful management of a patient with a large foeto-maternal haemorrhage. This incident supported the need for the procedural enhancements already underway. This critical incident re-emphasised the need for the planned systems improvements to be introduced quickly.