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Letter to the Editor
Dual-colour flow cytometry for the analysis of fetomaternal haemorrhage during delivery
  1. Waltraut M Merz1,
  2. Franziska Patzwaldt2,
  3. Rolf Fimmers3,
  4. Birgit Stoffel-Wagner4,
  5. Ulrich Gembruch1
  1. 1Department of Obstetrics and Prenatal Medicine, University of Bonn Medical School, Bonn, Germany
  2. 2University of Bonn Medical School, Bonn, Germany
  3. 3Institute for Medical Biometry, Informatics and Epidemiology, University of Bonn Medical School, Bonn, Germany
  4. 4Institute for Clinical Chemistry and Pharmacology, University Bonn Medical School, Bonn, Germany
  1. Correspondence to Dr Waltraut M Merz, Department of Obstetrics and Prenatal Medicine, University of Bonn Medical School, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany; waltraut.merz{at}

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Flow cytometry is an established method for the detection of fetomaternal haemorrhage (FMH). Compared with the Kleihauer-Betke test it is less labour-intensive and more accurate.1 Single-colour tests utilise antibodies against RhD antigen or fetal haemoglobin (HbF). The ‘Fetal Cell Count Kit’ (IQ products, Groningen, The Netherlands), a test for the diagnosis of FMH by dual-colour flow cytometry, is registered for ‘in vitro diagnostic use’ in the European Union (‘research use only’ in all other countries). Antibodies are directed against HbF and erythrocyte carbonic anhydrase (CA), taking advantage of the fact that considerable synthesis of red blood cell (RBC) CA commences only after birth. This allows the distinction between three cell populations present in the circulation of pregnant women: fetal RBCs (HbF cells) (HbF+/CA−); adult HbF-containing RBCs (F-cells) (HbF+/CA+), present in adult circulation at a mean concentration of 4.07±2.78% of RBCs and increased in pregnancy and various haemoglobinopathies; and adult RBCs (HbF−/CA+). The method has been validated against the Kleihauer technique in vitro and in vivo.2 The low detection limit and high accuracy permit quantification of FMH over a wide range of measurements.

Our objective was to analyse the frequency of FMH during delivery and to investigate maternal, fetal and obstetric factors associated with FMH incidence and volume.

Women attending our obstetric department for delivery between April and October 2008 were considered for enrolment. The study was undertaken in accordance with the regulations of the institutional ethics committee on clinical research. Informed consent was obtained …

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