**4.4 Absence of facility to monitor the antibody titre and quantification in pregnant women who have developed HDFN causing alloantibody during pregnancy**

Haemolytic Disease of the Foetus and Newborn (HDFN) is the destruction of foetal and newborn red cells by maternally derived alloantibody directed against a red cell antigen often inherited from the father and expressed on foetal cells. These maternal IgG antibodies are low molecular weight and can pass through the placenta barrier into the foetal circulation and bind to the corresponding foetal red cell antigen. The resultant maternal IgG-coated cells interact with foetal macrophages in resulting in their removal by the foetal spleen. This often results in anaemia, erthroblastosis with compensatory erythropoiesis resuming in the foetal liver and spleen, resulting in hepatosplenomegaly and portal hypertension. Maternal antibody screening is undertaken to detect clinically significant antibodies, which might affect the foetus and/or newborn, and to detect antibodies that may cause problems with the provision of compatible blood products for the woman and for the foetus/newborn. Approximately 1% of pregnant women are found to have clinically significant red cell antibodies [107–109]. The detection of clinically significant antibodies among antenatal women plays an important role in transfusion safety and preventing HDFN. A previous study among antenatal multiparous women in Jammu region of India indicated that the commonly observed alloantibodies were anti-D, anti-E, anti-C and anti-K [110]. Once an antibody has been detected, it is identified by carrying out a panel test. If the antibody specificity is one that has the potential to cause HDFN, the titre/quantification must be carried out periodically. Antibody quantification and titration is performed on patients' samples, to support the prediction and management of HDFN and ABO mismatched organ transplant. Antibody quantification of anti-D, and anti-c for management of HDFN. Antibody titration in ABO mismatched transplant is carried out to allow clinical assessment of the possibility of carrying out an ABO mismatched transplant, and monitoring of treatment to reduce antibody titre in preparation for ABO mismatched transplant. All clinically significant maternal antibodies detected during antenatal booking or follow up visit must be referred to the reference laboratory for confirmation of specificity, determination of the possibility of the antibody to cause HDFN and for and titre/quantification to allow for the monitoring of antibody. Evidence based best practice in developed countries requires the monitoring of women with red cell antibodies of specificities known to have potential to cause significant HDFN (anti-D, anti-c and anti-K), covering frequency of testing (every 4 weeks from booking until 28 weeks and every 2 weeks there after till delivery), measurement of antibody concentration (by quantification or titration as appropriate), referral to a foetal medicine specialist and followup required post-delivery. Antibodies that require quantification include anti-c, anti D, anti c + D, and anti-c + E. The antibodies that require titration include Anti-e, c, E, C+ e, G, CW, Fya, Fyb, K, k, Kpa, Kpb, Jsa, Jsb, M, S, and s. Antibody titration (ABT) is a semi quantitative method used to detect the strength of an alloantibody/antibodies present in the patient's plasma [111]. Antibody titration is used prenatally to screen for risk of HDFN, haemolytic transfusion reactions and assessment in solid organ or haematopoietic stem cell transplant. To assess risk for HDFN, the titre of the clinically significant alloantibody is performed. When the antibody and the titre strength are identified, ABT is periodically performed throughout pregnancy, whereby plasma samples are compared in parallel with the previously frozen samples to determine if the titre or strength of the antibody is static, decreasing or increasing. Obstetricians can use this information in conjunction with middle cerebral artery Doppler assessment to determine the extent to

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*Distribution of Clinically Relevant Blood Group Antigens among Nigerians…*

which the developing infant is affected, the presence of foetal anaemia, decision to carry out intrauterine transfusion as well as decision on whether to deliver the baby earlier to allow for a better and less risky physical management rather than ultrasound-guided in utero management [112]. Colour Doppler ultrasonography a non-invasive technique is currently being used to assess cerebral artery blood flow [113]. Increased cerebral artery blood flow is an indicator of foetal anaemia [114]. Invasive procedures such as amniocentesis or cordocentesis, with subsequent analysis of amniotic fluid and foetal blood sampling obtained by ultrasonography guided procedure are invasive and significantly risky with potential attendant negative effect to the foetus. Accepted titration methodologies include the tube and gel column technology method [115]. A difference of 2 dilutions or a score of 10 is usually an indication of significant change in antibody production. The antibody titre/quantification often rises as a result of re-exposure of the maternal immune system to red cell antigen following the initial sensitising events that occur during pregnancy. Every re-exposure to the initial offending antigen from the foetus to the mother's immune system often becomes booster doses. These booster doses often result in more antibody production, attendant increase in the titre and quantification. Antibody titration is also commonly used for screening blood products, particularly platelets and plasma as well as group O donor blood intended for transfusion to blood group A, B and AB patients. This is to decrease the risk of haemolytic transfusion reactions due to passive anti-A/anti-B antibodies. The titre of group O products is determined and those with high titers [51, 114] are labelled and used for group O individuals only while those negative for HT haemolysin can be given to A, B and AB individuals [116]. Also, ABT also has a potential role in preventing graft rejection in ABO-incompatible solid organ transplants (heart, liver, and lung) [117] as well as in erythroid engraftment after haematopoietic progenitor cell transplants [118]. Previous report indicates that the performance of antenatal titrations by column agglutination technology (CAT) is at least as sensitive as the performance by the indirect antiglobulin test (IAT) tube method. CAT was found to show greater sensitivity than IAT tube when dealing with anti-c compared to titrating Anti-K. The CAT method also appears to be more sensitive for detecting samples that require referral to the obstetrician [119]. Evidencedbased best practice requires that all pregnant women are tested for the presence of alloantibodies and its titers/quantification during pregnancy as a way of calculating

the risk of developing HDFN [120]. Guidelines of the British Committee for standards in Haematology requires that, all pregnant women should be ABO and D antigen typed and screened for presence of alloantibodies at booking and at the 28th week of gestation [121]. Similarly, in the Netherlands, it has been mandatory to screen all pregnant females for presence of alloantibodies [122]. The aim of periodic antibody titration and quantification (every 4 weeks from detection at booking till 28 weeks and every 2 weeks thereafter until delivery) is to determine whether the titre/quantification is static, decreasing or increasing. A static titre/ quantification shows that there is no increase in severity over time, a dropping titre/quantification indicate a low risk for HDFN while a rising titre/quantification is an indication of a potentially severe HDFN. For anti-D quantification a level of 4–15 IU indicates a moderate risk while a level > 15 IU indicates a high risk for HDFN. For anti-c a level > 7.5 IU indicates a high risk of HDFN. For anti-K, a titre of 1:32 or greater is indicative of HDFN risk. Generally, a 4-fold increase in the titre of an HDFN-associated alloantibody is an indication of a significant risk for HDFN [68]. In Nigeria and some other African countries alloantibody testing at booking and at 28 weeks gestation is not available, facilities for alloantibody identification and titration/quantification is not available. A number of pregnant women have alloantibodies without knowing and the risk of mortality from HDFN is high.

*DOI: http://dx.doi.org/10.5772/intechopen.90372*

### *Distribution of Clinically Relevant Blood Group Antigens among Nigerians… DOI: http://dx.doi.org/10.5772/intechopen.90372*

which the developing infant is affected, the presence of foetal anaemia, decision to carry out intrauterine transfusion as well as decision on whether to deliver the baby earlier to allow for a better and less risky physical management rather than ultrasound-guided in utero management [112]. Colour Doppler ultrasonography a non-invasive technique is currently being used to assess cerebral artery blood flow [113]. Increased cerebral artery blood flow is an indicator of foetal anaemia [114]. Invasive procedures such as amniocentesis or cordocentesis, with subsequent analysis of amniotic fluid and foetal blood sampling obtained by ultrasonography guided procedure are invasive and significantly risky with potential attendant negative effect to the foetus. Accepted titration methodologies include the tube and gel column technology method [115]. A difference of 2 dilutions or a score of 10 is usually an indication of significant change in antibody production. The antibody titre/quantification often rises as a result of re-exposure of the maternal immune system to red cell antigen following the initial sensitising events that occur during pregnancy. Every re-exposure to the initial offending antigen from the foetus to the mother's immune system often becomes booster doses. These booster doses often result in more antibody production, attendant increase in the titre and quantification. Antibody titration is also commonly used for screening blood products, particularly platelets and plasma as well as group O donor blood intended for transfusion to blood group A, B and AB patients. This is to decrease the risk of haemolytic transfusion reactions due to passive anti-A/anti-B antibodies. The titre of group O products is determined and those with high titers [51, 114] are labelled and used for group O individuals only while those negative for HT haemolysin can be given to A, B and AB individuals [116]. Also, ABT also has a potential role in preventing graft rejection in ABO-incompatible solid organ transplants (heart, liver, and lung) [117] as well as in erythroid engraftment after haematopoietic progenitor cell transplants [118]. Previous report indicates that the performance of antenatal titrations by column agglutination technology (CAT) is at least as sensitive as the performance by the indirect antiglobulin test (IAT) tube method. CAT was found to show greater sensitivity than IAT tube when dealing with anti-c compared to titrating Anti-K. The CAT method also appears to be more sensitive for detecting samples that require referral to the obstetrician [119]. Evidencedbased best practice requires that all pregnant women are tested for the presence of alloantibodies and its titers/quantification during pregnancy as a way of calculating the risk of developing HDFN [120]. Guidelines of the British Committee for standards in Haematology requires that, all pregnant women should be ABO and D antigen typed and screened for presence of alloantibodies at booking and at the 28th week of gestation [121]. Similarly, in the Netherlands, it has been mandatory to screen all pregnant females for presence of alloantibodies [122]. The aim of periodic antibody titration and quantification (every 4 weeks from detection at booking till 28 weeks and every 2 weeks thereafter until delivery) is to determine whether the titre/quantification is static, decreasing or increasing. A static titre/ quantification shows that there is no increase in severity over time, a dropping titre/quantification indicate a low risk for HDFN while a rising titre/quantification is an indication of a potentially severe HDFN. For anti-D quantification a level of 4–15 IU indicates a moderate risk while a level > 15 IU indicates a high risk for HDFN. For anti-c a level > 7.5 IU indicates a high risk of HDFN. For anti-K, a titre of 1:32 or greater is indicative of HDFN risk. Generally, a 4-fold increase in the titre of an HDFN-associated alloantibody is an indication of a significant risk for HDFN [68]. In Nigeria and some other African countries alloantibody testing at booking and at 28 weeks gestation is not available, facilities for alloantibody identification and titration/quantification is not available. A number of pregnant women have alloantibodies without knowing and the risk of mortality from HDFN is high.

Nigerian and most of these countries can afford to provide the best possible antenatal care for their pregnant population like it obtains in the developed world. However, lack of political will, failure in stewardship and endemic corruption and misappropriation of the people's resources remains a major challenge to the effective management of the women. African government must rise to the responsibilities and do what is right by implementing evidence-based practice to allow for the effective management of pregnancies associated with clinically significant alloantibodies and its associated HDFN.
