Feto-maternal haemorrhage investigation

Keywords: Haemoglobin F, Feto-maternal haemorrhage investigation - flow cytometry

Specimen:

5 mL blood in EDTA tube.

Method:

A fluorochrome conjugated IgG monoclonal anti-D reagent is used to label D positive fetal cells. Flow cytometry is used to detect and quantify the minor population in the D negative maternal sample. Other tests using antibodies to alternative markers (eg, HbF) are also used. Cytoplasmic staining for HbF with anti-HbF monoclonal antibody.

Application:

Detection and quantitation of suspected feto-maternal haemorrhage (FMH). This includes in Rh D negative women following delivery of a Rh D positive baby and following all potentially sensitising events in Rh D negative women after 20 weeks gestation.

Repeat testing following confirmed FMH and administration of anti-D immunoglobulin may be required depending on the volume of the FMH.

May also be used to test for a minor D positive population in D negative women of childbearing potential following other potentially sensitising events such as D positive red cell transfusion.

The flow cytometric method provides a more accurate and objective quantitation of fetal cells in the maternal circulation and is the recommended reference method to confirm the volume of FMH. See also the acid elution method, which is most suited to screening for FMH. The use of these methods will depend on local availability

Interpretation:

The proportion of fetal cells is calculated as a percentage of all red cells. The report should provide the result of the FMH test in ‘mL fetal red cells’ to inform the dose of anti-D immunoglobulin required.

Reference:

Working Party of the British Committee for Standards in Haematology, Transfusion Taskforce. Guidelines for the Estimation of Fetomaternal Haemorrhage 2009. London: British Society for Haematology, 2009.