Revisiting the full blood count: Circulating blood cells and their role in coagulation.

There has been an expansion in our understanding of the multifaceted roles of circulating blood cells in regulating haemostasis and contributing to thrombosis. Notably, there is greater recognition of the interplay between coagulation with inflammation and innate immune activation and the contribution of leucocytes. The full blood count (FBC) is a time-honoured test in medicine; however, its components are often viewed in isolation and without consideration of their haemostatic and thrombotic potential. Here, we review how the individual components of the FBC, that is, haemoglobin, platelets and leucocytes, engage with the haemostatic system and focus on both their quantitative and qualitative attributes. We also explore how this information can be harnessed into better management of people with multiple long-term conditions because of their higher risk of adverse clinical events.

Major reduction in occurrence of anti-c and anti-E in pregnancy after more than 10 years of preventive matched transfusion with most benefit for c-matching.

Extension with cE-matching of the transfusion policy for women under 45 years to prevent alloimmunization and hemolytic disease of the foetus and newborn (HDFN) was evaluated. After implementation of cEK-matching, anti-c occurrence decreased from 46.8 to 30.4 per 100 000 pregnancies (RR 0.65, 95% CI 0.54-0.79), while anti-E occurrence decreased from 122.1 to 89.9 per 100 000 pregnancies (RR 0.74, 95% CI 0.66-0.84). The c-negative women showed a higher anti-E occurrence before cEK-matching and a more pronounced decline with the new policy. This indicates that cEK-matched transfusion effectively reduces alloimmunization, and that a cK-matched approach could prevent most transfusion-related alloimmunization and HDFN.

Autoimmune anti-D in an RhD-positive young infant: Learning from a rare case.

BACKGROUND AND OBJECTIVES: Anti-D is usually immune in nature and is formed in individuals lacking D antigen or having variants/altered D phenotypes. In the Indian population, 93.8% are RhD positive, and R1 R1 is the commonest Rh phenotype. Here we report a rare and interesting case of autoimmune anti-D in an RhD-positive 3-month-old infant leading to warm autoimmune haemolytic anaemia. STUDY DESIGN AND METHODS: Auto-anti-D was detected serologically by immunohaematological techniques such as direct antiglobulin test, antibody detection and identification, dithiothreitol, enzyme treatment, antibody titration and elution. Molecular studies were performed to rule out genetic variants of RhD. RESULTS: Anti-D was confirmed in eluate and blood group post elution was B RhD positive. On genotyping using the Indian-specific RHD genotyping assay, the sample was found to be negative for the RHD*01W.150 (most common RhD variant in Indians) but positive for RHD exon 5 and RHD exon 10 along with glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The sample was further sequenced for RHD exons 1-10 by Sanger sequencing and found to be a wild type, thus, ruling out the presence of an RhD variant. CONCLUSION: This case is of interest because of the rare occurrence of autoimmune anti-D in an RhD-positive patient of such a young age (3 months). To the best of our knowledge, only two case reports have been published on autoimmune anti-D in infancy (in 1961 and 1964).

Epidemiological and clinical features, therapeutic strategies and outcomes in patients with hyperhaemolysis: A systematic review.

Hyperhaemolysis syndrome (HHS), a severe form of delayed haemolytic transfusion reaction most commonly described in patients with sickle cell disease (SCD), involves destruction of both donor and recipient red blood cells (RBCs). As the epidemiology and underlying pathophysiology have yet to be definitively elucidated, recognition can be challenging. We systematically reviewed PubMed and EMBASE to identify all cases of post-transfusion hyperhaemolysis and characterized the epidemiological, clinical and immunohaematological characteristics and treatments of HHS. We identified 51 patients (33 females and 18 males), including 31 patients with SCD (HbSS, HbSC and HbS/ß-thalassaemia). The median haemoglobin nadir (3.9 g/dL) occurred a median of 10 days post-transfusion. 32.6% and 45.7% of patients had a negative indirect anti-globulin test and a negative direct anti-globulin test, respectively. The most common therapies included corticosteroids and intravenous immune globulin. 66.0% of patients received ≥1 supportive transfusion, which was associated with a longer median hospital stay/time to recovery (23 days vs. 15 days; p = 0.015) compared to no supportive transfusion. These findings illustrate that HHS that often results in marked anaemia 10 days post-transfusion is not restricted to patients with haemoglobinopathies, and additional transfused RBCs may be associated with a longer time-to-recovery.

Prevalence of adsorbed A antigen onto donor-derived group O red cells in children following stem cell transplantation: A single-centre evaluation.

BACKGROUND AND OBJECTIVES: A group AB D-positive child presented 1 year after haematopoietic stem cell transplant (HSCT) from a group O D-negative donor as group A D-negative. Engraftment remained at 100% in white cell lineages. The reason for the unusual result was explored, and the scarcely reported phenomenon of adsorption of secreted antigen was considered. This study also investigated the prevalence of secreted antigen adsorbed onto donor-derived group O red blood cells (RBCs) in children after HSCT and defined a process for laboratory management. MATERIALS AND METHODS: Retrospective data analysis of HSCTs carried out over 19 months at Great Ormond Street Hospital was conducted to identify cases of adsorbed A antigen after HSCT. Investigation of RBC reactions with different clones of anti-A and in vitro experiments was performed to recreate adsorption. RESULTS: Nineteen A to O HSCTs were conducted over 19 months, of which six (31%) displayed weak A antigen on RBCs despite full myeloid engraftment. Negative reactions with anti-A were obtained when run on an alternative clone. Laboratory protocols for the future management of these cases have been developed. CONCLUSION: Passive adsorption of secreted antigen is responsible for these results and is more widespread than previously reported, as a third of A to O HSCTs at our centre demonstrated this phenomenon. A process has been implemented into the laboratory to manage this cohort, ensuring component groups compatible with both donor and recipient are given, and the shared care centres are aware of these requirements.

The complexities of transfusion reactions: Coexistence of a delayed haemolytic transfusion reaction and post-transfusion purpura.

BACKGROUND AND OBJECTIVES: Immune-mediated acute or delayed transfusion reactions occur when there is immunological incompatibility between transfused blood products and recipient's antibodies. Acute haemolytic transfusion reactions occur within 24 h and are delayed after 24 h up to 10 days following transfusion, whereas post-transfusion purpura (PTP) typically occurs 7-10 days post-transfusion. We present a case of a previously transfused and recently post-partum female who developed both delayed haemolytic transfusion reaction (DHTR) and PTP. CASE REPORT: A 42-year-old woman, G2P1, with non-alcoholic liver disease, portal hypertension and previous transfusion history with allogeneic anti-E, developed a severe DHTR and PTP following a complicated post-partum course and multiple transfusions. The antenatal and initial post-partum pre-transfusion antibody screens were negative. Subsequently five red cell antibodies, including anti-c, anti-Fya, anti-Jkb and anti-S and the reappearance of anti-E were, however, identified during follow-up investigations along with the anti-platelet antibody HPA-3a and human leukocyte antigen class I antibodies. Anti-E, anti-Jkb and anti-S were eluted from the circulating red blood cells. CONCLUSION: To our knowledge, there have been only two other case reports of DHTR and PTP occurring in the same patient.

Transplant-associated thrombotic microangiopathy and immune haematological complications following intestine-containing organ transplantation: experience from over 100 consecutive cases.

Descriptions of passenger lymphocyte syndrome (PLS), immune cytopenias and transplant-associated thrombotic microangiopathy (TA-TMA) after intestine-containing transplants remain scarce. We describe our centre's experience of these complications from 2007 to 2019. Ninety-six patients received 103 transplants. PLS occurred in 9 (9%) patients (median 12 days post-transplant); all due to ABO antibodies. There were 31 minor ABO mismatch transplants. No patient required change in immunosuppression. Immune cytopenias (excluding PLS) occurred in six patients at an incidence of 1·7/100 patient years; three immune haemolysis, one immune thrombocytopenia, one acquired Glanzmann's and one immune neutropenia; 50% occurred with other cytopenias. All cases eventually responded to treatment, with a median of four treatments (range 1-8) and 5/6 were treated with rituximab. One patient with immune haemolysis required bortezomib. Complications were common in patients with immune cytopenias; 4/6 with infection needing intravenous antibiotics and 3/6 with venous thromboembolism. In 3/6 cases, a secondary cause for the immune cytopenia was evident. Switching from tacrolimus to ciclosporin was not necessary. There were five cases of transplant-associated thrombotic microangiopathy (TA-TMA; 1·5/100 patient years) requiring calcineurin inhibitor withdrawal; two cases associated with acute rejection. Two cases were managed with plasma exchange, one with plasma infusions and one with eculizumab. Further research in this patient group is required.

Clinical consequences of the extremely rare anti-PP1Pk isoantibodies in pregnancy: a case series and review of the literature.

BACKGROUND: The absence of the red cell antigens P, P1 and Pk , known as 'p', represents an extremely rare red cell phenotype. Individuals with this phenotype spontaneously form anti-PP1Pk isoantibodies, associated with severe haemolytic transfusion reactions, recurrent spontaneous abortion and haemolytic disease of the fetus and newborn (HDFN). METHODS: We report a series of four successful pregnancies in three women with anti-PP1Pk isoantibodies, one complicated by HDFN, another by intrauterine growth restriction, all managed supportively. We also review the literature regarding the management of pregnancy involving anti-PP1Pk isoimmunization. RESULTS: The literature surrounding anti-PP1Pk in pregnancy is limited to a very small number of case reports. The majority report management with therapeutic plasma exchange (TPE) with or without intravenous immunoglobulin. The relationship between titre and risk of pregnancy loss remains unclear, though a history of recurrent pregnancy loss appears important. Although a positive cord blood direct antiglobulin test is frequently noted, clinically significant HDFN appears uncommon, though possible. CONCLUSION: Early initiation of TPE in high risk patients should be strongly considered. If possible, pregnancies should be managed in a high-risk obstetric or maternal fetal medicine service. The fetus should be monitored closely with interval fetal ultrasound and middle cerebral artery peak systolic volume Doppler to screen for fetal anaemia. Timely sourcing of compatible blood products is likely to be highly challenging, and both directed and autologous donation should be contemplated where appropriate. The International Red Cell Donor Panel may also provide access to compatible products.

Alloimmunisation rate of patients on Daratumumab: A retrospective cohort study of patients in England.

OBJECTIVE: Whilst small-scale studies on rates of alloimmunisation of patients on Daratumumab have been undertaken, no large-scale study has been performed to date on this cohort of patients. BACKGROUND: Patients with multiple myeloma (MM) who are relapsed or refractory to standard treatment are treated with the anti-CD38 therapeutic monoclonal antibody, Daratumumab. Due to the complexity of pre-transfusion compatibility testing, many MM patients in England are referred to Red Cell Immunohaematology (RCI) laboratories for investigation and provision of Red Blood Cell (RBC) components. METHODS: Over a 4-month period, patients due to commence, or currently on anti-CD38 therapy were identified and flagged on the RCI Laboratory Information Management System (LIMS). Data was identified and extracted for further analysis. Interrogation of data was performed independently by two subject matter experts, with discrepancies resolved through further enquiry. RESULTS: Of 734 English MM patients, we report an alloimmunisation rate of 0.4% whilst on an anti-CD38 TMAb. This is in line with other smaller cohort studies. CONCLUSION: Given the low rate of RBC alloimmunisation, consideration should be given to revising the pre-transfusion testing regimen in this cohort. This may improve testing costs, turn-around times and evidence-based patient care.

Mass cytometry identifies expansion of double positive and exhausted T cell subsets in the tumour microenvironment of patients with POEMS syndrome.

We sought to dissect the tumour microenvironment in a small cohort (N = 10) of patients with POEMS at diagnosis and after therapy using mass cytometry. We included 10 MGUS patients as controls. We identified 29 immune cell subsets in the CD45+ and CD3+ compartments. Double positive T cells and PD-1 positive CD4 T cells were expanded and naïve CD4 T cells were decreased in the bone marrow of patients with newly diagnosed/progressing POEMS. These findings provide evidence for possible antigenic-driven selection as a driver of disease pathogenesis in POEMS.

Soluble mediators in packed red blood cells augment lipopolysaccharide-induced monocyte interleukin-1ß production.

BACKGROUND AND OBJECTIVES: Soluble mediators in packed red-blood-cell (PRBC) units have been hypothesized as a mechanism associated with transfusion-related immune modulation. Soluble mediators including damage-associated molecular patterns (DAMPs) are known to activate inflammasomes. Inflammasome complexes maturate caspase-1 and interleukin (IL)-1ß. We assessed whether PRBC supernatants (SN) modulated IL-1ß driven inflammation and whether macrophage migration inhibitory factor (MIF) was a contributing factor. MATERIALS AND METHODS: Isolated monocytes were incubated with PRBC-SN in an in vitro transfusion model. Lipopolysaccharide (LPS) was added in parallel to model a bacterial infection. Separately, recombinant MIF was used in the model to assess its role in IL-1ß driven inflammation. IL-1ß and caspase-1 were quantified in the PRBC-SN and culture SN from the in vitro model. RESULTS: PRBC-SN alone did not induce IL-1ß production from monocytes. However, PRBC-SN alone increased caspase-1 production. LPS alone induced both IL-1ß and caspase-1 production. PRBC-SN augmented LPS-driven IL-1ß and caspase-1 production. Recombinant MIF did not modulate IL-1ß production in our model. CONCLUSIONS: Soluble mediators in PRBC modulate monocyte IL-1ß inflammation, which may be a contributing factor to adverse effects of transfusion associated with poor patient outcomes. While MIF was present in PRBC-SN, we found no evidence that MIF was responsible for IL-1ß associated immune modulation.

Risk of RBC alloimmunization in multiple myeloma patients treated by Daratumumab.

BACKGROUND: Daratumumab (DARA) is a human monoclonal antibody for the treatment of multiple myeloma (MM). DARA binds to CD38 on RBCs and interferes with detection of RBC alloantibodies. The objective of this study was to evaluate the risk of RBC alloimmunization in MM patients treated with DARA. MATERIALS AND METHODS: A retrospective study of the complete serological profile and transfusion history of 45 MM patients received transfusion and treated with DARA from July 2015 to December 2018 was undertaken. All cases with positive Ab screens were treated with DTT to identify RBC alloantibodies. RBC transfusion history was monitored between the first DARA dose to the last or extending to the first negative Ab screen after the last DARA dose if the Ab screen was ever positive. Forty-six MM patients received transfusion but not DARA were studied as control group. RESULTS: Totally 184 Ab screens were done on 45 patients transfused with ABO-Rh compatible RBCs, phenotypically matched units or both. None of them showed detectable alloantibodies after DTT treatment. The duration of Ab screening positivity varied markedly, ranging from 25 days to 5 months after the last dose. Two of 46 patients in the control group had preexisting alloantibodies but no new alloantibodies were detected during study period. CONCLUSIONS: Our results indicate that the risk of forming new RBC alloantibodies after transfusion in MM patients treated with current regimens is very low and no DARA-associated difference in the alloimmunization risk. No significant difference in alloimmunization is detected between ABO-Rh compatible and phenotypically matched transfusion.

A Japanese multi-institutional collaborative study of antigen-positive red blood cell (RBC) transfusions in patients with corresponding RBC antibodies.

BACKGROUND AND OBJECTIVES: It is sometimes difficult to obtain antigen-negative red blood cells (RBCs) for patients with antibodies against RBCs. However, the frequency and severity of the adverse reactions have not been well elucidated. Here, we conducted a multi-institutional collaborative study to clarify the background, frequency and clinical significance of antigen-positive RBC transfusions to patients with the respective antibodies. MATERIALS AND METHODS: The survey included the background of patients, antigens on RBCs transfused, total amount of antigen-positive RBCs transfused, results from antibody screen and direct antiglobulin tests, specificity of antibodies, adverse reactions and efficacies. All antibodies were surveyed regardless of their clinical significance. RESULTS: In all, 826 cases containing 878 antibodies were registered from 45 institutions. The main reasons for antigen-positive RBC transfusions included 'negative by indirect antiglobulin test' (39%) and 'detection of warm autoantibodies' (25%). In 23 cases (3% of total), some adverse reactions were observed after antigen-positive RBC transfusion, and 25 antibodies (9 of 119 clinically significant and 16 of 646 insignificant antibodies) were detected. Non-specific warm autoantibodies were detected in 9 cases, anti-E in 5 cases, 2 cases each of anti-Lea , anti-Jra or cold alloantibodies, and 1 case each of anti-Dib , anti-Leb or anti-P1. Other antibodies were detected in 2 further cases. Five (22%) of these 23 cases, who had anti-E (3 cases) or anti-Jra (2 cases), experienced clinically apparent haemolysis. CONCLUSIONS: Adverse reactions, especially haemolysis, were more frequently observed in cases with clinically significant antibodies than those with clinically insignificant antibodies (P < 0·001).

An exploration of the advantages of automated titration testing: low inter-instrument variability and equivalent accuracy for ABO and non-ABO antibody titres relative to tube testing.

BACKGROUND AND OBJECTIVES: Obtaining IgM and IgG titres is important in numerous clinical situations, including solid-organ transplant, obstetrics, and for testing of out-of-group plasma-containing components. Tube method is the most prevalent testing modality, though it is both labour-intensive and known for intra- and inter-laboratory variability. The utility of automated gel testing as a method to improve both inter- and intra-laboratory reproducibility is unknown. MATERIALS AND METHODS: Two academic centres participated in a study evaluating automated gel titreing. Group O plasma samples were used to measure titres of antibodies against ABO (IgM) with buffered gel cards and 4 minor and minor red-blood-cell antigens (IgG) anti-IgG gel cards. Multiple ORTHO VISION automated analyzers were used to assess inter-instrument variation. A subset of ABO (IgM) samples were compared between laboratories to evaluate inter-laboratory variability. Multiple samples were titred by tube and by automated gel technology to determine similarity of results. RESULTS: Testing demonstrated no significant difference between analysers or between sites when performing automated titrations (P ≥ 0·99). Non-ABO IgG titres were evaluated and demonstrated little inter-instrument variability. The IgM anti-A and -B titres obtained by automated gel testing were neither consistently higher nor lower than tube titres. Greater than 90% of titre values were within one dilution. CONCLUSION: Based on this study, our data suggest that titreing by automated gel testing is both highly reproducible (IgM and IgG) and does not differ significantly from manual tube testing results of direct agglutination (IgM).

Characterization of RHD alleles present in serologically RHD-negative donors determined by a sensitive microplate technique.

BACKGROUND AND OBJECTIVES: Weak D phenotypes with very low antigen densities and DEL phenotype may not be detected in RhD typing routine and could be typed as D-negative, leading to D alloimmunization of D-negative recipients. The present study aimed to investigate the presence of RHD-positive genotypes in blood donors typed as D-negative by an automated system using the solid-phase methodology as a confirmatory test. METHODS: Two screenings were performed in different selected donor populations. For the first screening, we selected 1403 blood donor samples typed as D-negative regardless of the CE status, and in the second screening, we selected 517 donor samples typed as D-negative C+ and/or E+. RhD typing was performed by microplate in an automated equipment (Neo-Immucor®), and the confirmatory test was performed by solid-phase technique using Capture R® technology. A multiplex PCR specific to RHD and RHDψ was performed in a pool of 6 DNA samples. Sequencing of RHD exons was performed in all RHD-positive samples, and a specific PCR was used to identify the D-CE(4-7)-D hybrid gene. RESULTS AND CONCLUSION: No weak D type was found in either screening populations. Additionally, 353 (18·4%) D-negative samples presented previously reported non-functional RHD genes, 2 samples had a DEL allele, and 6 samples demonstrated new alleles, including one novel DEL allele. Our study identified six new RHD alleles and showed that the inclusion of a confirmatory test using serological methodology with high sensitivity can reduce the frequency of weak D samples typed as D-negative.

Extending shelf life of dithiothreitol-treated panel RBCs to 28 days.

BACKGROUND: Daratumumab (DARA) causes non-specific results in indirect agglutination testing (IAT). Dithiothreitol (DTT) treatment of panel red blood cells (RBCs) abolishes DARA interference. The objective of our study was to extend stability of DTT-treated panel RBCs to 28 days through application of a commercially available panel RBC stabilizer. MATERIALS AND METHODS: Serological antigen typing and IAT using DARA sera and DARA plasma spiked with weakly reacting alloantibodies was performed up to 28 days after DTT treatment and stabilization. RESULTS: DTT treatment resulted in loss of Fy-antigen expression on some panel RBCs. Antigen profiles of stabilized, DTT-treated panel RBCs remained stable. Alloantibodies in DARA sera and DARA plasma were reliably detected. CONCLUSIONS: Application of a commercially available RBC stabilizer extends shelf life of DTT-treated panel RBCs to 28 days.

Evidence for the positive impact of ISO 9001 and ISO 15189 quality systems on laboratory performance - evaluation of immunohaematology external quality assessment results during 19 years in Austria.

Background ISO 9001 and ISO 15189 have been established as continuative models for quality systems beyond national laws, mandatory standards and guidelines of expert associations regarding analytical and organisational performance of medical laboratories and transfusion services. Although widely used, their impact on laboratory performance has not been investigated. Methods We retrospectively analysed the results of 167 laboratories in 59 distributions of the Austrian red cell immunohaematology external quality assessment (EQA) scheme in the years 1999-2017. The performance for each parameter and trends of individual participants were compared with respect to certification or accreditation status of participants' quality systems and to laboratory type. Results Considering more than 52,000 EQA results, the absence or presence of a laboratory quality management system showed different error rates. Laboratories with ISO 9001 or ISO 15189 certification/accreditation had 0.7% incorrect results, while this rate was doubled without such quality systems (1.4%, p=0.0002). Statistically significant error reductions were seen upon ISO 9001/ISO 15189 implementation (1.3% before vs. 0.7% after; p=0.0468). Transfusion services had fewer errors (0.9%) compared to hospital and independent laboratories (both 1.2%). Conclusions Implementation and maintenance of quality systems according to ISO 9001 or ISO 15189 as well as laboratory specialisation result in better analytical performance as can be seen in immunohaematology EQA results. The conclusion is that these results apply to other laboratory tests and perhaps to other areas of health care.

Considerations for pre-transfusion immunohaematology testing in patients receiving the anti-CD38 monoclonal antibody daratumumab for the treatment of multiple myeloma.

In recent years, the anti-CD38 monoclonal antibody daratumumab (Darzalex; Janssen-Cilag Pty Ltd) has been shown to be highly efficacious in relapsed and refractory multiple myeloma, with the final results of treatment in newly diagnosed patients awaited. Despite awareness of the potential interference of daratumumab in pre-transfusion immunohaematology testing during phase I and II clinical studies, there was a degree of unpreparedness in the community upon the introduction of this drug into the clinics, particularly the impact that it has on the operational processes in hospital transfusion laboratories and timely issue of red blood cells (RBCs). Anti-CD38 interference in pre-transfusion immunohaematology tests is a particular problem in patients being treated with daratumumab for multiple myeloma as many will require RBC transfusions during their disease treatment. Panagglutination caused by anti-CD38 monoclonal antibody during the indirect antiglobulin test may mask the presence of a clinically significant RBC alloantibody in the patient's plasma during the antibody screen and identification process, which may be overlooked, particularly in urgent situations, subsequently resulting in a delayed or acute haemolytic transfusion reaction. Here, we summarise daratumumab's effects on pre-transfusion immunohaematology testing and its impact on clinical practice and make practical recommendations based on a consensus from medical and scientific transfusion experts and myeloma specialists on behalf of the Australian and New Zealand Society of Blood Transfusion and Myeloma Scientific Advisory Group to Myeloma Australia, respectively.

Prevalence and risk factors for red blood cell alloimmunization in 175 children with sickle cell disease in a French university hospital reference centre.

Patients with sickle cell disease (SCD) show a high prevalence of red blood cell (RBC) alloimmunization, but few studies have focused on children. We aimed to study the prevalence and risk factors of RBC alloimmunization in SCD children. We retrospectively analysed the medical and transfusion files for 245 SCD children hospitalized in our centre in 2014 and included 175 patients who had received at least one RBC unit in their lifetime. The main clinical and immuno-haematological characteristics of alloimmunized and non-alloimmunized patients were compared. The prevalence of alloimmunization was 13·7% [95% confidence interval (CI) (8·6-18·6)], and 7·4% [95% CI (3·5-11·3)] after excluding the probable irregular natural antibodies (anti-M, anti-Lea , anti-Leb , anti-Lex ). Main risk factors for alloimmunization were increased number of RBC units received (median of 65 vs. 10 units per patient; P = 0·01) and the presence of one or more red cell autoantibodies (46·2% vs. 4·7%; P < 0·0001). The alloimmunization rate was higher for episodically transfused than chronically transfused patients (1·43 vs. 0·24/100 units received; P < 0·001). The presence of red cell autoantibodies appears to be a major risk factor for alloimmunization in SCD children and could justify specific transfusion guidelines.

Genetic background of the rare Yus and Gerbich blood group phenotypes: homologous regions of the GYPC gene contribute to deletion alleles.

The GYPC gene encodes the glycophorins C and D. The two moieties express 12 known antigens of the Gerbich blood group system and functionally stabilize red blood cell membranes through their intracellular interaction with protein 4.1 and p55. Three GYPC exon deletions are responsible for the lack of the high-frequency antigens Ge2 (Yus type, exon 2 deletion), Ge2 and Ge3 (Gerbich type, exon 3 deletion), and Ge2 to 4 (Leach type, exons 3 and 4 deletion), but lack exact molecular description. A total of 29 rare blood samples with Yus (GE:-2,3,4) and Gerbich (GE:-2,-3,4) phenotypes, including individuals of Middle-Eastern, North-African or Balkan ancestry were examined genetically. All phenotypes could be explained by 4 different Yus alleles, characterized by deletions of exon 2 and adjacent introns, and 3 different Gerbich alleles, with deletions of exon 3 and adjacent introns. A 3600 base pair GYPC region, encompassing exon 2 and flanking region, shares a high degree of sequence homology with a region flanking exon 3, probably representing an evolutionary duplication event. Defining the expression of Gerbich variants presently relies on rare serological reagents. Our approach substitutes the serological characterization with a precise genotype approach to identify the rare Yus and Gerbich alleles.