A near-miss hemolytic transfusion reaction and hemolytic disease of the newborn due to anti-c antibodies in a Rh (D)-positive mother: Implications for immunohematological management in pregnancy.

Sir,

Though Anti-D continues to be commonest cause of severe hemolytic disease of fetus and newborn (HDFN), other blood group antibodies are also known to cause HDFN and hemolytic transfusion reactions.[1] In India, however, antibody screening is limited to Rh (D)-negative mothers. We report here a case of hemolytic disease of newborn (HDN) and near-miss hemolytic transfusion reaction due to anti-c identified in an Rh (D)-positive mother because of crossmatch incompatibility.

Two blood group identical blood units were issued for an urgent request of blood after Immediate Spin Crossmatch (IST crossmatch) for a B Rh (D)-positive patient having life-threatening postpartum hemorrhage (PPH). According to standard operating procedure for pretransfusion testing for urgent requests, crossmatch by Indirect Antiglobulin Test (IAT) using LISS Coombs Gel card (Diamed AG, Switzerland) was also put up after issue to confirm the absence of clinically significant antibodies in patient serum. On IAT crossmatch, the units issued were found to be incompatible (3+) indicating presence of clinically significant antibodies in her serum. The transfusion has not been started till then and blood units were immediately called back for further workup.

Our case was a 33-year-old lady, Para two, who recently delivered a male via full-term normal vaginal delivery. Her elder child was delivered six years back and had no history of neonatal hyperbilirubinemia after birth. She was transfused two units of blood during Mitral valve replacement surgery done 10 years back. In this pregnancy, she was not screened for irregular antibodies.

Her serum was screened for irregular antibodies using a commercial three cell antibody screening Panel (Diacell, Diamed AG, Switzerland) and LISS Coombs Gel cards (Diamed AG, Switzerland). Test was positive with SC II (4+) and SC III (4 +) suggestive of probability of anti c, E, K, Fyb, Jka, Jkb, S, and anti M. On testing with 11 cell identification panel (ID DiaPanel, Diamed AG, Switzerland), it was confirmed to be anti-c antibody. In the absence of inventory of minor antigen typed blood, ten B Rh(D)-positive units were typed for c antigen to find c-negative compatible unit for issue which further delayed the transfusion.

The titer of anti-c in mother serum was 64 (score 69) using O-positive and homozygous c-positive red cells. The consultant obstetrician was informed and neonate's sample was sought for workup of HDFN. The blood group of baby was O Rh(D)-positive. DAT was 4+ by tube technique, using polyspecific anti-human globulin as well as by LISS Coombs gel card (Diamed, Switzerland). Monospecific DAT (Diamed) was IgG only (4+), with subtype IgG1 (2+) and IgG3 (1+). Anti-c was identified in the eluate obtained from neonate's RBCs by acid elution method (Gamma elukit, Immucor Gamma, USA). The Rh phenotype and most probable genotype of mother was DCe/R1R1, whereas child and father were DCce/R1Ro or R1r. Thus, the infant and father were heterozygous for c antigen. HDN due to anti-c was diagnosed and other investigations initiated. There was no hydrops or hepatosplenomegaly in the neonate at birth. At 24 hours, the total serum bilirubin, hematocrit, and hemoglobin were 8.0 mg/dl, 56%, and 18.3 g/dl, respectively. The bilirubin level increased to 12 mg/dl at 48 hours. The newborn responded well to phototherapy and was discharged after 7 days; any exchange transfusions were not required.

Major obstetric hemorrhage remains the leading cause of maternal morbidity and mortality worldwide. Clinically significant irregular red cell antibodies (Anti-D, c, C, E, e. Kell, Kidd, Duffy and MNSs blood group antibodies) develop as a result of immunization by previous transfusion or fetomaternal incompatibility. These antibodies can cause HDFN and delayed hemolytic transfusion reaction and can result in significant delay in providing compatible blood.[1]

In the present case, the immediate transfusion request was sent by the clinician due to the presence of high risk factors, i.e., history of transfusion, previous cardiac surgery, and previous obstetric history. She presented in advanced stage of labor and coincidentally had PPH of moderate degree because of which blood was required urgently. Patients who urgently receive red blood cells (RBCs) before completion of routine blood bank testing remain at risk for non-ABO alloantibody-mediated hemolytic transfusion reactions. The reaction was prevented from occurrence because of awareness and diligence on part of staff. Such events are termed as near-miss events. Antibody card was given to mother with the advice for care during future transfusion and pregnancies. Studies have demonstrated that the release of RBCs before completion of testing carries a risk of 1.5% units or 2.6% episodes of receipt of antigen incompatible RBCs and a low risk (0.4%) of non-ABO alloantibody-mediated HTRs.[2] Therefore, clinicians must weigh the risk and benefit of sending the immediate requests.

Screening for non-RhD antibodies in all pregnant women has been implemented in most developed countries. Anti-c, with or without anti-E, is reported in about 0.7 per 1 000 pregnant women.[3] According to a north Indian study, the incidence of RBC alloimmunization in transfused patients is reported to be 3.4% (18/531), with anti-c being the most common specificity (38.8%).[4] In a study from the USA, fetuses from 46 of 55 pregnancies with anti-c had a positive direct antiglobulin test and eight of the affected neonates had HDN requiring fetal transfusion, although no perinatal deaths were reported due to anti-c. An antibody titer of 1 : 32 or greater or the presence of hydrops identified all affected fetuses.[5] In present case, the titer of maternal anti-c was higher than the critical titer, along with strong positive DAT in newborn with anti-c in eluate which went undetected during pregnancy.

This case points toward the growing body of evidence for a need to develop guidelines and infrastructure for antenatal antibody screeningfor timely detection of pregnancies at risk of severe HDFN as well as timely identification of clinically significant antibodies, if a blood transfusion to the mother is necessary during delivery.