Red blood cell alloimmunization in sickle cell disease patients in Uganda

BACKGROUND: Blood transfusion is an integral part in the management of sickle cell disease (SCD) patients. Alloimmunization is a recognized complication of red blood cell (RBC) transfusions with consequences including delayed hemolytic transfusion reactions and difficulties in getting compatible blood for future transfusions. The objective of this study was to determine the frequency of RBC alloimmunization in SCD patients in Uganda where pretransfusion screening for alloantibodies is not practiced.
STUDY DESIGN AND METHODS: In a cross-sectional study, SCD patients at Mulago Hospital Sickle Cell Clinic, Kampala, Uganda, were investigated. The demographic characteristics and transfusion history were recorded. Blood samples were drawn from consenting, previously transfused patients and RBC alloimmunization was demonstrated using immunohematologic techniques.
RESULTS: There were 428 patients (median age, 12 years; female/male ratio, 1.0) and they had received a median of 3 units in a median of three transfusion episodes. Twenty-six patients (6.1%) possessed RBC alloantibodies and 21 (80.7%) of them had received up to 10 transfusions. A total of 30 alloantibodies was found; 20 (66.7%) and 5 (16.6%) belonged to Rh and MNS blood groups, respectively. Five of the alloimmunized patients had multiple antibodies.
CONCLUSIONS: The rate of RBC alloimmunization in Ugandan SCD patients was 6.1%. The homogeneity between donors and SCD patients plus the low transfusion load may explain this immunization frequency. Nevertheless, our study confirms the significance of RBC alloimmunization as a complication in Ugandan SCD patients. Therefore, there is need to improve immunohematologic testing in Uganda so that RBC alloimmunization and its consequences may be prevented.     

Red blood cell alloimmunization in sickle cell disease: prevalence in 2010

BACKGROUND: Transfusion of red blood cells (RBCs) is frequently required for care of individuals with sickle cell disease (SCD). Alloimmunization rates are high and may be reduced by matching for RBC antigens that can cause alloimmunization. STUDY DESIGN AND METHODS: During the PROACTIVE Feasibility Study, patients with SCD age 2 years or older admitted for pain without acute chest syndrome were enrolled for possible randomization to preventive blood transfusion or standard care. Transfusion and antibody histories were obtained at each site, and antibody screening was done, to assess transfusion burden and alloimmunization prevalence. Participating sites were surveyed regarding antigen matching practice. RESULTS: A total of 237 patients (169 SS, 42 SC, 15 Sβ⁰‐thalassemia, 11 Sβ⁺‐thalassemia), 118 males and 119 females, were enrolled. Mean age was 19.3 years (range, 2.0‐68.0); there were 122 children and 115 adults. A total of 75.8% had received at least a single transfusion of RBCs before the study. Thirty‐four patients (14.4%) had a history of at least one alloantibody and 17 of these had more than one. When surveyed, 19 sites (83% of responders) reported antigen matching to at least include C, E, and K for transfusion of all patients with SCD. CONCLUSION: Though antigen typing before transfusion of people with SCD and providing antigen‐negative units is now widely employed by sickle cell centers, the alloimmunization rate remains quite high in contemporary sickle cell populations and may be due in large part to transfusions received at institutions not providing extended matching.     

Perinatal implications of sickle cell disease

Sickle cell disease (SCD) affects millions of people across the globe. In the United States, approximately 70,000 to 100,000 people have the disease, and 2 million have the sickle cell trait. SCD occurs once in every 500 African American births, and once in 36,000 Hispanic American births. Women with SCD can have more adverse maternal outcomes such as preeclampsia, eclampsia, preterm labor, placental abruption, intrauterine growth restriction, and low birthweight. Providing comprehensive nursing care to women with SCD is a challenge, particularly during labor and birth, with nursing management aimed at attaining healthy birth outcomes while preventing or treating manifestations of the disease. Labor and delivery nurses are responsible for specific knowledge and care practices for these women, including differentiating the pain of sickle cell crisis from contraction pain and monitoring maternal and fetal oxygenation, as oxygenation is jeopardized in laboring sickle cell patients. Intrapartum nursing care also requires vigilance in the need for emergency cesarean birth. Nursing interventions include symptom management, pain management, ensuring patient safety, and educating patients. Coordination of care and clear communication between the members of the healthcare team, patient, and family are essential elements to ensure a positive outcome for perinatal patients with SCD.     

Characterization of circulating and cultured Tfh-like cells in sickle cell disease in relation to red blood cell alloimmunization status

BackgroundPeople living with sickle cell disease (SCD) are prone to red blood cell (RBC) alloimmunization. We hypothesized that subjects with alloantibodies (responders) would have differences in circulating T-follicular helper (Tfh)-like cells compared to subjects without alloantibodies (non-responders).Materials and methodsPeripheral blood mononuclear cells were collected from 28 subjects, including those with SCD and controls. Circulating CD4 T-cell subsets were first evaluated at baseline. CD4 T-cell subsets were also evaluated after naïve CD4 T-cells were differentiated into Tfh-like cells following in vitro culture with CD3/CD28 beads, IL-7, IL-12, and Activin A. Transfusion and alloantibody histories were extracted from the electronic medical record.ResultsNon-responders had a lower percentage of CD45RA negative Tmemory cells than responders or controls (p<0.05). Notably, there were no differences in circulating Tfh-like cells between any group. However, naïve CD4 T-cells from subjects with SCD were more likely to express CXCR5 after in vitro culture than cells from controls. After culture, CXCR5 expressing cells from responders were more likely to express PD1 and ICOS (16.43 %, sd. 20.23) compared to non-responders (3.69 %, s.d. 3.09) or controls (2.78 %, s.d. 2.04).DiscussionThe tendency for naïve CD4 T-cells from responders to differentiate into Tfh-like cells after in vitro culture may suggest these cells are prepared to assist B-cells with antibody production regardless of antigen specificity. Further studies are needed, but it is possible that these results may explain why some responders form RBC alloantibodies with multiple specificities, in addition to RBC autoantibodies and HLA alloantibodies.     

Chronic red blood cell exchange to prevent clinical complications in sickle cell disease.

We tracked the results of 394 manual or automatic red blood cell exchanges done with a cell separator in 20 sickle cell patients at high risk for recurrent complications. Over an average of 6 years, none of the patients developed complications related to the procedure or to the increased blood use. It was safe and effective in preventing complications of sickle cell disease, and if done automatically, reduced iron overload. Ferritin levels also decreased in patients treated with automatic red blood cell exchange. Furthermore, using Single Donor Red Blood Cell units (SDRC) we reduced the potential exposure to transfusion transmitted infectious diseases (TTI).     

Partial C antigen in sickle cell disease patients: clinical relevance and prevention of alloimmunization

BACKGROUND: Partial Rh antigens have been widely described in black individuals. Carriers are prone to immunization when exposed to the normal antigens. In sickle cell disease (SCD), patient alloimmunization is a major cause of transfusion failure. The potential of individuals with partial C antigen to make anti-C has not been investigated. We sought partial C status and anti-C production in a cohort of SCD patients with the C+ phenotype, to determine whether exposure to normal C antigen should be avoided.
STUDY DESIGN AND METHODS: We constituted a cohort of 177 randomly selected SCD patients expressing C antigen. We screened for (C)ce^s and R^N haplotypes, presumably associated with partial C antigen in Afro-Caribbeans, and we recorded the number of transfused C+ red blood cell (RBC) units, immunization status, and extended phenotype.
RESULTS: Forty-nine patients carried abnormal C antigen, deduced from the presence of (C)ce^s and/or R^N , not compensated by a normal RHC allele in trans. Among patients with partial C phenotype exposed repeatedly to C+ RBCs, 30% produced anti-C. Two patients experienced hemolysis. In our hospital, with 22% of SCD patients expressing C, prevention of anti-C immunization for all individuals with partial C antigen would require a 7% increase in the use of C– RBC units. These RBCs are already in short supply for SCD patients who are C–.
CONCLUSION: This study demonstrates the need to detect partial C within C+ SCD patients and to prevent immunization. A larger number of Afro-Caribbeans donors is needed to provide these patients with C– RBCs.     

High frequency of partial DIIIa and DAR alleles found in sickle cell disease patients suggests increased risk of alloimmunization to RhD

We have set out to determine the frequency of DIIIa and DAR alleles among sickle cell disease (SCD) patients. These D variants permit the unexpected development of antibodies to RhD among individuals who are otherwise classified as RhD+. DNA samples from 130 SCD patients were tested for 455A>C (specific for DIIIa), 602C>G, 667T>G (common for both DIIIa and DAR) and 1025T>C (specific for DAR) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequence analysis. The PCR-RFLP showed that 12 (9.2%) of the SCD patients were carrying DIIIa and DAR alleles. Genomic DNA analysis performed by sequence showed that three samples were heterozygous DIIIa (2.3%), seven heterozygous DAR (4.6%) and two (1.5%) samples carried a partial D with four mutations: 455A>C (heterozygous), 602C>G and 667T>G (homozygous) and 1025T>C (heterozygous), indicating compound heterozygosity for one DIIIa allele and one DAR allele. The predicted phenotypes of eight (6.2%) SCD patients were DIIIa, DAR and DIIIa/DAR. Three patients were anti-D immunized (DAR, n = 1; DIIIa/DAR, n = 2). These findings suggest that SCD patients who are candidates for chronic transfusion may benefit from genotyping for DIIIa and DAR to prevent alloimmunization.     

Lower alloimmunization rates in pediatric sickle cell patients on chronic erythrocytapheresis compared to chronic simple transfusions

BACKGROUND: Erythrocytapheresis (ECP), automated red blood cell exchange, is increasingly being used for chronic transfusion therapy in sickle cell disease (SCD) as it is an isovolumetric transfusion, is more effective in lowering hemoglobin (Hb)S, and can limit iron overload. Because ECP requires increased blood exposure compared to simple transfusions there is concern for increased transfusion complications, including alloimmunization. We compared alloimmunization rates between patients receiving simple or exchange chronic transfusions. STUDY DESIGN AND METHODS: Data were retrospectively collected for 45 SCD patients (n = 23 simple, n = 22 ECP) on a chronic transfusion program as of December 2010 to determine the rate of antibody formation (antibodies formed per 100 units transfused). RESULTS: The 45 patients received 10,949 units and formed six new alloantibodies during the study period (1994‐2010); therefore, the overall alloimmunization rate was 0.055 alloantibodies per 100 U. There were three antibodies formed in three patients on ECP, one allo (anti‐rh_i) and two autoantibodies. There were six antibodies in four patients on a simple transfusion program, five allo (anti‐Le^a, M, D, C, and Kp^a) and one autoantibody. The ECP group received significantly more blood (338.5 units/patient vs. 152.2 units/patient, p = 0.001). The rate of antibody formation (auto plus allo) was 0.040 antibodies per 100 U in the ECP group and 0.171 antibodies per 100 U in the simple transfusion group (p = 0.04). The alloantibodies formed per 100 units was 0.013 in the ECP group and 0.143 in the simple transfusion group (p = 0.03). CONCLUSION: Chronic ECP should be considered in patients requiring optimal management of HbS levels and iron burden. Concerns about increased alloimmunization with ECP may be unjustified.     

Opportunities to improve outcomes in sickle cell disease

Sickle cell disease represents a spectrum of inherited hemoglobin disorders. The pathophysiology involves abnormalities not just in red blood cells but also vascular endothelium, white blood cell function, coagulation, and inflammatory response. Known sequelae of sickle cell disease include invasive infections, painful episodes, acute chest syndrome, strokes, and chronic pulmonary hypertension. Preventive strategies that decrease the risk of infection are the routine use of daily antibiotics until five years of age, immunization of children with the 7-valent pneumococcal conjugate vaccine in addition to the 23-valent polysaccharide pneumococcal vaccine, annual influenza vaccination after six months of age, and meningococcal vaccination after two years of age. A significant advance in stroke prevention is the use of transcranial Doppler ultrasonography to identify asymptomatic, at-risk children who should be considered for chronic blood transfusions. Chronic transfusion therapy for primary or secondary stroke prevention requires careful surveillance for iron overload and chelation therapy. Patients with chest pain, fever, or respiratory symptoms and new pulmonary infiltrates require aggressive medical management for acute chest syndrome. Pain management still represents an important area for aggressive treatment using sickle cell disease-specific guidelines. Newer treatments include hydroxyurea therapy to decrease the frequency of painful episodes and associated comorbidities, and hematopoietic cell transplantation for a limited subset of patients. Family physicians play a crucial role in instituting evidence-based preventive care strategies, initiating timely treatment of acute illness, recognizing life-threatening episodes, and providing a medical home for multidisciplinary management.