Antibodies that cause haemolytic disease of the fetus and newborn (HDFN) are IgG antibodies made in response to exposure of fetal red blood cells (RBCs) during pregnancy and delivery. The most common antibodies found to cause HDFN are directed against D, c, K, C, E, Fy^a antigens on the fetal RBCs. There are the following severe symptoms of HDFN: anaemia, hepatic dysfunction, hydrops fetalis, heart failure, brain damage by the unconjugated bilirubin crossing the blood--brain barrier and even death. In such cases, intrauterine transfusions are needed to save the fetus (1-4). Mothers can be alloimmunised to RBC antigens because of spontaneous haemorrhage of fetal RBCs into the maternal circulation. The volumes of fetomaternal haemorrhage (FMH) are usually small, about 0.5 ml of erythrocytes. In 1% of mothers FMH is bigger than 3 ml and in 0.3% bigger than 15 ml. Number of HDFN cases due to anti-D has been reduced since specific immunoprophylaxis was introduced in the ‘70s. Anti-D immunoglobulin (Ig) neutralizes RhD positive fetal RBCs in the circulation of mother and protects her against alloimmunization (4-8). The postpartum standard dose of anti-D Ig in Poland is 150 μg, which can neutralize 7.5 ml of fetal RhD positive RBCs. In other countries, anti-D Ig doses vary from 100 to 300 μg. Despite of the use of immunoprophylaxis, from 1 to 2% women produce allo-anti-D. In some countries (for example United Kingdom, Ireland), all RhD negative mothers are tested after labour for detection and quantification of FMH and if it is necessary, the dose of anti-D Ig is increased. Microscopic or flow cytometry tests usually base on detection of the cells containing fetal haemoglobin (HbF) between cells with adult haemoglobin (HbA). If a test for the detection of RhD antigen is used, it is applicable only when the mother is RhD negative and the fetus is RhD positive. Results from flow cytometry tests with anti-HbF or anti-RhD have very good sensitivity and specificity but these methods require special expensive equipment (9-16). Gel agglutination technique to screen the FMH could be used in many serological laboratories, where serological gel microcolumn tests for grouping, crossmatching and antibody screening (DiaMed, Switzerland) are routinely performed. It is semiquantitative method based on the consumption of anti-D antibodies by RhD positive fetal RBCs, indirectly measured by the use of RhD positive indicator RBCs. When fetal RhD positive RBCs are absent or their percentage is smaller than 0.1%, the reaction with indicator cells is strong (4+), but when in mother’s blood sample there is > 0.4% of fetal cells, all anti-D bind to fetal antigens and reaction with indicator cells is negative (fig. 1).

The aim of this study was to implement and evaluate column agglutination method ID-FMH Screening-Test (DiaMed, Switzerland) for the detection of RhD positive fetal RBCs in the blood of RhD negative mothers.