Red blood cell antibody screening in pregnancy

Sir, 
 
Hemolytic disease of newborn (HDN) is defined as neonatal anemia and hyperbilirubinemia caused by an incompatibility between maternal and fetal red blood cells (RBCs).[1] In 98% cases it is caused due to ABO and Rh incompatibility and antibodies to other blood group antigens (Kell, c, E, C, Kidd, Duffy, M, and so on) are causative in remaining 2%.[2] More than 43 different RBC antigens have been reported to be associated with HDN.[3] Red cell antibody screening (RCAS) is a valuable tool in the detection of alloantibodies to other blood group systems (other than ABO and Rh) in the serum of patients during pregnancy or prior to transfusion. Red cell antibody identification (RCAI) should then be carried out on a larger panel of RBCs to precisely identify the antibody. 
 
In a prospective study carried out on 624 antenatal cases, RCAS was done using a 3-cell panel from Diamed, Switzerland. RCAI was carried out on cases that were positive for RCAS. RCAS was positive in 9 out of 624 cases—1.4% (excluding the 3 cases who had autoantibodies). After RCAI these were identified as anti-D antibody (6 cases, 66%), anti-D with anti-C antibody (2 cases, 22%), and anti-M antibody (1 case, 11%). 
 
The most common antibody identified remained anti-D. In 2 cases of Rh negative pregnancy, the RCAS was suggestive of anti-D. RCAI done, however, showed a combination of anti-D and anti-C. One case of anti-M was detected in a G2P1L1D1 lady. The first pregnancy was full-term normal delivery at home, however, the baby died after birth. The mother’s and baby’s blood group was O positive. RCAS done during second pregnancy was suggestive of anti-Duffy (Fya) or anti-M antibody. RCAI done showed anti-M antibody with dosage effect. The second pregnancy was postdated with Intrauterine growth retardation (IUGR,) and Lower segment caesarean section(LSCS) was done for fetal distress. The baby had hyperbilirubinemia and was Direct Coombs test (DCT) positive requiring phototherapy. 
 
Rh incompatibility continues to be a common cause for HDN. Patients with no prior history of sensitization can also develop anti-D as seen in 3 of our cases probably due to naturally occurring anti-Rh antibodies or antepartum hemorrhage. Despite the use anti-D immunization, 1%–2% of the cases are still sensitized. Anti-D immunization resulted in a favorable fetal outcome in the study. Anti-D complicated with anti-C presents with more severe HDN as seen in 1 patient who had a previous stillbirth and a hydrops baby despite receiving anti-D. Anti-C antibodies resulting in HDN requiring exchange transfusion have been reported.[4] 
 
Anti-M as a cause of HDN is rare as they are usually complete cold antibodies (IgM). However, it can be IgG type resulting in HDN.[3] HDN due to anti-M antibody can be mild to severe with stillbirth and cases requiring exchange transfusion have been reported.[5] Anti-M causing blood group discrepancy and crossmatch incompatibility has been reported in the Indian literature.[6] 
 
Antenatal detection of the non-anti-D causes of HDN requires RCAS. If RCAS is positive, the following steps are to be taken. RCAI should be done to identify the antibody. The spouse has to be screened for the presence of offending antigen and the pediatrician has to be alerted about delivery of a potentially sensitized infant. The blood bank should find a suitable antigen-negative donor for transfusion to baby and mother.


Letters to the Editor
Sir, Hemolytic disease of newborn (HDN) is defined as neonatal anemia and hyperbilirubinemia caused by an incompatibility between maternal and fetal red blood cells (RBCs). [1] In 98% cases it is caused due to ABO and Rh incompatibility and antibodies to other blood group antigens (Kell, c, E, C, Kidd, Duffy, M, and so on) are causative in remaining 2%. [2] More than 43 different RBC antigens have been reported to be associated with HDN. [3] Red cell antibody screening (RCAS) is a valuable tool in the detection of alloantibodies to other blood group systems (other than ABO and Rh) in the serum of patients during pregnancy or prior to transfusion. Red cell antibody identification (RCAI) should then be carried out on a larger panel of RBCs to precisely identify the antibody.
In a prospective study carried out on 624 antenatal cases, RCAS was done using a 3-cell panel from Diamed, Switzerland. RCAI was carried out on cases that were positive for RCAS. RCAS was positive in 9 out of 624 cases-1.4% (excluding the 3 cases who had autoantibodies). After RCAI these were identified as anti-D antibody (6 cases, 66%), anti-D with anti-C antibody (2 cases, 22%), and anti-M antibody (1 case, 11%).
The most common antibody identified remained anti-D. In 2 cases of Rh negative pregnancy, the RCAS was suggestive of anti-D. RCAI done, however, showed a combination of anti-D and anti-C. One case of anti-M was detected in a G 2 P 1 L 1 D 1 lady. The first pregnancy was full-term normal delivery at home, however, the baby died after birth. The mother's and baby's blood group was O positive. RCAS done during second pregnancy was suggestive of anti-Duffy (Fy a ) or anti-M antibody. RCAI done showed anti-M antibody with dosage effect. The second pregnancy was postdated with Intrauterine growth retardation ( IUGR,) and Lower segment caesarean section( LSCS) was done for fetal distress. The baby had hyperbilirubinemia and was Direct Coombs test (DCT) positive requiring phototherapy.
Rh incompatibility continues to be a common cause for HDN. Patients with no prior history of sensitization can also develop anti-D as seen in 3 of our cases probably due to naturally occurring anti-Rh antibodies or antepartum hemorrhage. Despite the use anti-D immunization, 1%-2% of the cases are still sensitized. Anti-D immunization resulted in a favorable fetal outcome in the study. Anti-D complicated with anti-C presents with more severe HDN as seen in 1 patient who had a previous stillbirth and a hydrops baby despite receiving anti-D. Anti-C antibodies resulting in HDN requiring exchange transfusion have been reported. [4] Anti-M as a cause of HDN is rare as they are usually complete cold antibodies (IgM). However, it can be IgG type resulting in HDN. [3] HDN due to anti-M antibody can be mild to severe with stillbirth and cases requiring exchange transfusion have been reported. [5] Anti-M causing blood group discrepancy and crossmatch incompatibility has been reported in the Indian literature. [6] Antenatal detection of the non-anti-D causes of HDN requires RCAS. If RCAS is positive, the following steps are to be taken. RCAI should be done to identify the antibody. The spouse has to be screened for the presence of offending antigen and the pediatrician has to be alerted about delivery of a potentially sensitized infant. The blood bank should find a suitable antigen-negative donor for transfusion to baby and mother.

Nanobiotechnology and blood substitutes
Sir, Nanobiotechnology is the assembling of biological molecules into 1-100 nm dimensions. These dimensions can be the diameter of nanodimension artificial cells or particles; membranes with nanodimension thickness or nanotubules with nanodimension diameter. [1] Since red blood cell (RBC) membrane includes blood Red blood cell antibody screening in pregnancy group antigens, typing and matching are required earlier than they can be transfused into patients; these result in delays in emergency situations. The storage time using regular method is merely about 42 days. RBCs cannot be sterilized to remove infective agents like hepatitis viruses, HIV, and other probable emerging infective agents. Thus, RBCs substitutes are being developed. RBC contains hemoglobin (Hb), antioxidant enzymes, and multienzyme system to prevent the conversion of Hb into nonfunctioning met Hb. It has been shown as far back as 1957 that artificial RBC can be prepared with ultrathin polymer membranes of nanodimension thickness. To increase the circulation time, the first-generation engineered Hb is formed by using glutaraldehyde to crosslink Hb into soluble nanodimension polyhemoglobin (poly-Hb) that has been tested clinically in patients. Further extension includes conjugated Hb, intramolecularly crosslinked Hb, and recombinant Hb. For certain clinical uses, in addition to engineered Hb, antioxidants need to remove oxygen radicals to prevent injury from ischemia reperfusion. Nanobiotechnology is used to prepare second-generation engineered Hb by assembling Hb together with superoxide dismutase (SOD) and catalase (CAT) to form a nanodimension soluble complex of poly-Hb-CAT-SOD. A thirdgeneration system is to prepare nanodimension complete artificial RBCs that can circulate for sufficient length of time after infusion. One approach uses lipid vesicles to encapsulate Hb. Another approach to use biodegradable polymer-like polylactic acid or a copolymer of polyethylene glycol-polylactide (PEG-PLA) to form the membrane of nanodimension completes artificial RBC. [2] Past experience has shown that it takes many years to develop ideas on blood substitutes into products and that lack of basic information has resulted in much failure and delays. It is important to carry out basic research to gain important basic information needed for the simultaneous development of blood substitutes. In the meantime, two types of first-generation nanodimension poly-Hb are in the final stages of clinical trials in human and one of these has been approved for routine clinical uses in patients in South Africa. New nanodimension-conjugated Hb is also being tested in clinical trial. Shortage of human Hb is being resolved by studies on recombinant human Hb, placenta Hb, bovine Hb, and synthetic heme. Meanwhile, new generations of modified Hb are being developed that can modulate the effects of nitric oxide for those clinical applications that might have potential problems related to oxygen radicals. Poly-Hb can be crosslinked to an enzyme to suppress the growth of tumor. A further development is the use of PEG-lipids or PEG-biodegradable polymer membranes to prepare nanodimension artificial RBCs containing Hb and complex enzyme systems. Many other extensions and modifications of this general principle of blood transfusion in nanobiotechnology are possible. Sir, The prevalence of Bombay blood group (Oh Phenotype) in Andhra Pradesh state, South India, is not precisely known. Reported prevalence in the adjoining states of Tamil Nadu and Karnataka is 0.004 [1] and 0.005%, [2] respectively. Two recent population-based surveys in Chittoor district of Andhra Pradesh on ABO blood groups [3,4] do not even mention about this rare phenotype.
Hence, the authors from a tertiary care hospital in Andhra Pradesh, that is Sri Venkateswara Institute of Medical Sciences (SVIMS), Tirupati, in their investigation covering urban as well as rural population, screened at its blood bank, the Recipients and Donor subjects over a period of one and a half years to determine the prevalence of Bombay blood group. The relatives of the index cases were also included in the study.
The ABO and Rh-D typing were performed as per the AABB Technical Manual 16th Edition, 2008. Both cell and serum grouping were done. Red cell typing was done with commercial antisera and serum grouping was done using known cells from pooled blood units. All blood samples showing "O" group were tested with commercial anti-H lectin of Ulex europeus.
Saliva samples from all Bombay group persons were tested for ABO antigens by hemagglutination inhibition test. History of any consanguinity in the parents of Bombay group subjects was recorded. Analyzing the results of 26,638 study subjects showed that the most common group was "O" group (40.21%); 13 Oh phenotypes (0.048%) were detected -7 males and 6 females. Among these 13 Oh phenotypes, only 3 were Rh-D negative. Consanguinity among parents was observed in 10 cases (77%).