Multi-center study on mortality in children, and adults with sickle cell anemia-risk factors and causes of death.

Sickle cell disease (SCD) is a major public health burden worldwide with increasing morbidity and mortality. The study evaluates the risk factors associated with mortality in SCD patients, between the years 2006 and 2020 at three hospitals in Oman. The analysis includes clinical manifestations, haematological, biochemical, and radiological parameters, use of antibiotics, and blood and exchange transfusions. Our cohort included 123 patients (82 males, 41 females), with a median age of 27 (Interquartile Range 21-35 years). SCD related complications included acute chest syndrome (ACS) in 52.8%, splenic sequestration in 21.1%, right upper quadrant syndrome in 19.5%, more than > 6 VOC/year in 17.9%, and stroke in 13.8%. At the terminal admission, patients had cough, reduced O2 saturation, crepitation and fever in 24.4%, 49.6%, 53.6% and 68.3% respectively. Abnormal chest X-ray and chest CT scan were seen in 57.7%, and 76.4% respectively. Laboratory parameters showed a significant drop in hemoglobin (Hb) and platelet counts from baseline, with a significant rise in WBC, LDH and CRP from baseline (p < 0.05, Wilcoxon Signed Ranks test). All patients received antibiotics, whereas, 95.9% and 93.5% received simple blood transfusions, and exchange transfusions respectively, and 66.6% required non-invasive ventilation. Among the causes of death, ACS is seen in 32 (26%), sepsis in 49 (40%), and miscellaneous in 42 (34%). Sudden death was seen in 32 (26%) of patients. Male gender, with low HbF, rapid drop in Hb and platelet, and increased in WBC, LDH, ferritin, and CRP, correlated significantly with mortality in this cohort.

Impact of splenectomy on circulating microparticles in patients with sickle cell anemia.

INTRODUCTION: Circulating microparticles (MP) are being described as potential biomarkers for disease activity in a variety of conditions including sickle cell anemia (SCA). However, relatively little is known about the influence of spleen status on MP levels in patients with SCA. METHODS: Using a prospective study design we characterize circulating MP in 144 patients with SCA in steady state by assessing their cellular origin and their relationships to spleen status defined by clinical and imaging findings. In addition, MP levels were studied according to demographic characteristics, clinical status, treatment modalities, and other hematological and biochemical parameters. Absolute plasma concentrations of MP were determined by flow cytometry. RESULTS: Patients with SCA displayed a 10-fold increase in levels of MP derived from red blood cell (RBC) and platelets (PLT) when compared to their healthy counterparts (p < 0.0001). Splenectomized patients with SCA have more pronounced levels of MPRBC and MPPLT, and remained elevated after several weeks of follow-up. Levels of MP were not significantly associated with spleen removal procedures, age, gender, clinical severity score, hydroxyurea therapy, hemoglobin F, and co-existence of glucose-6-phosphate dehydrogenase deficiency. CONCLUSION: Collectively, these results suggest that splenectomy affects circulating levels of MP regardless of the known SCA modifiers and correlates.

Influence of Voxelotor-hemoglobin complexes in the estimation of hemoglobin S levels by the current standard of care laboratory evaluation techniques.

Background: Sickle cell disease is an inherited disorder characterized by the presence of sickle hemoglobin (HbS). The process of Hb molecule polymerization is a pivotal step in the sickling process. Voxelotor, a recently approved novel therapeutic agent, is known to interfere with polymerization. We aim to study the impact of Voxelotor on Hb variants analysis using high performance liquid chromatography (HPLC). Material and methods: We are reporting the impact of Voxelotor on Hb variants analysis using HPLC after an informed consent and medical research committee approval. Data was collected from eight patients who are enrolled in the GBT440-034OL study using electronic medical records, to evaluate the Hb levels, hemolytic markers and the clinical response. Results: Our patients were well-balanced for gender, with a mean age of 31.1 years (19-50). Six patients showed a significant improvement in the Hb level, with reduced reticulocytes, bilirubin, LDH and an improved clinical outcome. Interestingly, these patients showed the appearance of a split band of Hb S and D on HPLC impacting significantly on HbS level. Two patients did not show any improvement on laboratory parameters, and no changes on their HPLC analysis. Conclusions: We report here eight patients on Voxelotor therapy, six of which showed improved hemolytic markers and anemia and demonstrated the appearance of HbD peak on the HPLC chromatogram. Therefore, the absence of HbD on HPLC or other laboratory methods for estimating HbS in patients on Voxelotor therapy, gives the clinician a possible hint regarding the patient's compliance with the drug.

Novel PKLR missense mutation (A300P) causing pyruvate kinase deficiency in an Omani Kindred-PK deficiency masquerading as congenital dyserythropoietic anemia.

We report herein a child with transfusion-dependent chronic anemia, the cause of which was difficult to establish because of his transfusion dependency. The clinical and laboratory features suggested a chronic nonspherocytic hemolytic anemia (CNSHA) with bone marrow features suggestive of congenital dyserythropoietic anemia (CDA). DNA studies, however, revealed the underlying condition to be due to a novel mutation in the PKLR gene responsible for pyruvate kinase deficiency (PKD). Molecular investigations by a targeted next-generation sequencing (t-NGS) using a custom panel of 71 genes involved in the red blood cell (RBC) disorders revealed that the patient was homozygous for a novel missense mutation c.898G>C, p.Ala300Pro, whereas both his parents were heterozygous for the same mutation.

Measurement of hematopoietic progenitor cells using XN2000 hematology analyzer.

INTRODUCTION: Stem cell enumeration by the hematopoietic progenitor cells (HPC) mode is a novel method available from Sysmex XN2000 hematology analyzer. A small amount of blood (190 µL) is required, and the results are available in a few minutes without manual gating or presample treatment. The present study compares stem cell measurements using XN2000 analyzer HPC mode and FC500 flow cytometry analyzer using peripheral blood (PB) specimens and apheresis products. METHODS: In this prospective study, CD34-positive cell counts were enumerated using an FC500 flow cytometry analyzer and compared with XN2000 Sysmex analyzer (XN-HPC mode) in the same samples. Results were compared using Bland-Altman plots. RESULTS: A total of 103 samples were used. In the PB samples, the median HPC count and CD34-positive cells were 83.5 × 106 /L and 78.0 × 106 /L, respectively. The mean Bland-Altman difference was 4.5 × 106 /L (Limits: -51.7 to 60.7 × 106 /L), with a Pearson's correlation of 0.79. In the apheresis products, the median HPC count and CD34-positive cells were 1468 × 106 /L (IQR: 1049 - 1960 × 106 /L) and 1327 × 106 /L (IQR: 910 - 2001 × 106 /L), respectively. The mean Bland-Altman difference was 179.0 × 106 /L (Limits: -2022.2 - 2380.2 × 106 /L), with a Pearson's correlation of 0.58. CONCLUSION: The XN-HPC mode has an excellent correlation and minimal disagreement for stem cell enumeration in PB compared with flow cytometry and could replace it. There is high disagreement in apheresis products, and therefore, the XN-HPC mode cannot be recommended.

Predicting risk factors for thromboembolic complications in patients with sickle cell anaemia - lessons learned for prophylaxis.

OBJECTIVE: To assess the clinical and laboratory predictors of venous thromboembolism (VTE) in patients with sickle cell anaemia (SCA) and its relationship to morbidity and mortality. METHODS: This retrospective case-control study analysed data from patients with SCA that experienced VTE compared with matched control patients with SCA but no VTE (2:1 ratio). RESULTS: A total of 102 patients with SCA were enrolled (68 cases with VTE and 34 controls). Amongst the 68 cases (median age, 29.5 years), 26 (38.2%) presented with isolated pulmonary embolism (PE). A higher prevalence of splenectomy (73.5% versus 35.3%) was observed in the cases compared with the controls. A significantly higher prevalence of central venous catheter (CVC) insertion (42.6% versus 8.8%) was observed in the cases compared with the controls. High white blood cell counts, serum lactic dehydrogenase (LDH), bilirubin and C-reactive protein (CRP) and low haemoglobin (Hb) and HbF were significant risk factors for VTE. Forty-two cases (61.8%) developed acute chest syndrome, 10 (14.7%) had a stroke and seven (10.3%) died. CONCLUSIONS: VTE in patients with SCA has a high impact on morbidity and mortality. PE was the leading presentation of VTE, with CVC insertion, high LDH, bilirubin, CRP and white blood cell counts along with low Hb and HbF constituting other significant risk factors.

Iron Overload in Patients With Heavily Transfused Sickle Cell Disease-Correlation of Serum Ferritin With Cardiac T2* MRI (CMRTools), Liver T2* MRI, and R2-MRI (Ferriscan®).

The treatment of sickle cell disease (SCD) is mainly supportive, except for a minority, who receive bone marrow transplantation (BMT). Serum ferritin (SF) is routinely available but is notoriously unreliable as a tool for iron-overload assessment since it is an acute-phase reactant. Although blood transfusion is one of the most effective ways to deal with specific acute and chronic complications of SCD, this strategy is often associated with alloimmunization, iron overload, and hemolytic reactions. This study, thus, aims to evaluate iron overload in patients with SCD on chronic blood transfusions and specifically, correlate SF with the current standard of care of iron-overload assessment using MRI-based imaging techniques. Amongst a historic cohort of 58 chronically transfused patients with SCD, we were able to evaluate 44 patients who are currently alive and had multiple follow-up testing. Their mean age (±SD) was 35 (9) years and comprised of 68.2% of women. The studied iron-overload parameters included cardiac T2* MRI, liver iron concentration (LIC) by Liver T2* MRI, and serial SF levels. Additionally, in a smaller cohort, we also studied LIC by FerriScan© R2-MRI. Chronic blood transfusions were necessary for severe vaso-occlusive crisis (VOC) (38.6%), severe symptomatic anemia (38.6%), past history of stroke (15.9%), and recurrent acute chest syndrome (6.9%). About 14 (24%) patients among the original cohort died following SCD-related complications. Among the patients currently receiving chelation, 26 (96%) are on Deferasirox (DFX) [Jadenu® (24) or Exjade® (2)], with good compliance and tolerance. However, one patient is still receiving IV deferoxamine (DFO), in view of the significantly high systemic iron burden. In this evaluable cohort of 44 patients, the mean SF (±SD) reduced marginally from 4,311 to 4,230 ng/ml, mean Liver T2* MRI dropped from 12 to 10.3 mg/gm dry weight, while the mean cardiac T2*MRI improved from 36.8 to 39.5 ms. There was a mild to moderate correlation between the baseline and final values of SF ng/ml, r = 0.33, p = 0.01; Cardiac T2* MRI ms, r = 0.3, p = 0.02 and Liver T2* MRI mg/kg dry weight, r = 0.6, p < 0.001. Overall, there was a positive correlation between SF and Liver T2* MRI (Pearson's r = 0.78, p < 0.001). Cardiac T2*MRI increased with the decreasing SF concentration, showing a negative correlation which was statistically significant (Pearson's r = -0.6, p < 0.001). Furthermore, there was an excellent correlation between SF ng/ml and LIC by FerriScan© R2-MRI mg/g or mmol/kg (Spearmen's rho = -0.723, p < 0.008) in a small subset of patients (n = 14) who underwent the procedure. In conclusion, our study demonstrated a good correlation between serial SF and LIC by either Liver MRI T2* or by FerriScan© R2-MRI, even though SF is an acute-phase reactant. It also confirms the cardiac sparing effect in patients with SCD, even with the significant transfusion-related iron burden. About 14 (24%) patients of the original cohort died over the past 15 years, indicative of a negative impact of iron overload on disease morbidity and mortality.

Respiratory Viral Infections in Sickle Cell Anemia: Special Emphasis on H1N1 Co-infection.

OBJECTIVES: Patients with sickle cell anemia (SCA) are immunocompromised and at an increased risk of developing infections. Our aim was to establish the clinical, laboratory, and radiological manifestations of respiratory viral infections in SCA at Sultan Qaboos University Hospital (SQUH), Oman and assess its impact on disease morbidity and mortality, with special emphasis on H1N1. METHODS: We undertook a retrospective study in SCA patients with respiratory viral infections following up at the hematology department at SQUH. We collected demographic data and clinical, radiological, and laboratory parameters. RESULTS: In 84 SCA patients with 109 admission episodes for vaso-occlusive crisis (VOC), molecular diagnostic techniques confirmed 125 respiratory viral infections. Rhinovirus was the most prevalent infection (35.8%), whereas H1N1 virus infection was seen only in 10.1%. Laboratory investigations revealed a significant fall in mean hemoglobin levels, mean white blood cell, and platelet counts from baseline, whereas there was a significant rise in the mean lymphocyte and retic count, serum lactate dehydrogenase, and C-reactive protein levels during infective episodes (p < 0.050, Wilcoxon signed rank test). One-third (32.1%) of the VOC episodes progressed to acute chest syndrome (ACS), but in the H1N1 cohort, only two episodes of ACS was seen (18.2%). CONCLUSIONS: Rhinovirus was the commonest respiratory virus infections in SCA patients, whereas parainfluenza 3 was associated with a significant adverse outcome. H1N1 was associated with a mild course. ACS was seen in approximately one-third of this group of patients.

Predictors of impending acute chest syndrome in patients with sickle cell anaemia.

Acute chest syndrome (ACS) is a major complication of sickle cell anaemia (SCA) and a leading cause for hospital admissions and death. We aimed to study the spectrum of clinical and laboratory features of ACS and to assess the predisposing factors and predictors of severity. A retrospective case-control cohort was studied by retrieving patient information from electronic medical records after ethical approval. One hundred adolescents and adults with SCA and hospital admissions for ACS were identified through the discharge summaries, along with 20 additional patients presenting with VOC, but without ACS (controls). Among the patients with ACS, fever (>38.5 °C), reduced oxygen saturation (<95) and asplenia significantly differed when compared to those of controls (p < 0.05, chi-squared test). The degree of severity was reflected in the use of non-invasive ventilation (NIV), simple and exchange transfusions, and the presence of bilateral pleural effusions and multi-lobar atelectasis/consolidation, which were significantly higher in the cases with ACS than in the controls. Lower haemoglobin (Hb) and high WBC counts were also significantly different between the two groups (p < 0.05, Student's t test). Using logistic regression, our study further demonstrated that asplenia, fever, and reduced O2 saturation, along with low Hb and leukocytosis, were important predictors for the development of ACS.

Prevalence of Hepatitis B, Hepatitis C, and HIV in Multiply Transfused Sickle Cell Disease Patients from Oman.

BACKGROUND: In Oman, the prevalence of hepatitis B (HBV) infection is 5.8%, with 2.8-7.1% HBV carriers. Hepatitis C (HCV) prevalence among Omanis is 0.41%. A total of 2917 human immunodeficiency virus (HIV) infections were notified among Omanis by 2017. This study was performed as there was no data on the prevalence of HIV, HBV and HCV in sickle cell disease (SCD) patients from Oman. STUDY DESIGN AND METHODS: In this retrospective, cross-sectional study, medical records of all SCD patients who attended our hospital between 2011 to 2017 were retrieved from the hospital information system. Following approval by the local medical research and ethics committee, data on HIV, HBV, and HCV exposure were recorded to estimate the prevalence. RESULTS: Among a total of 1000 SCD patients (491 males and 509 females), twenty-three (2.3%) patients showed positive serology for hepatitis B surface antigen (HbsAg), of whom sixteen (1.6%) were HBV DNA positive. 126 (12.6%) had anti-HCV antibodies (anti-HCV), of whom fifty-two (5.2%) were HCV RNA positive. None of the patients had positive serology for HIV. A normal liver was observed on abdominal ultrasound in 788 (78.8%) patients, whereas 208 (20.8%) had hepatomegaly, and 4 (0.4%) had liver cirrhosis. Thirty-six (3.6%) patients died, but in only two patients, the mortality was due to cirrhosis of liver. CONCLUSIONS: This study provides the first comprehensive data on the prevalence of HBV and HCV infections among Omani SCD patients exposed to blood transfusions. Reassuringly, no case with HIV was observed.

Fresh frozen plasma (Octaplas) and topical heparin in the management of ligneous conjunctivitis.

Ligneous conjunctivitis is a rare form of chronic recurrent membranous conjunctivitis with reduced plasminogen activity. It is characterized by the formation of characteristic firm ("woody") membranes on the tarsal conjunctiva. Similar lesions may occur on other mucous membranes. When treated with local excision, ligneous conjunctivitis is invariably associated with recurrences. Various therapeutic modalities, including topical heparin, cyclosporine, fresh frozen plasma (FFP), plasminogen, and amniotic membrane transplantation have been reported to reduce postoperative recurrences. We present 2 cases of recurrent ligneous conjunctivitis in children successfully managed with surgical excision under cover of FFP transfusion, amniotic membrane grafting, and combined with concomitant postoperative administration of topical heparin, steroids.

Effect of CYP4F2, VKORC1, and CYP2C9 in Influencing Coumarin Dose: A Single-Patient Data Meta-Analysis in More Than 15,000 Individuals.

The cytochrome P450 (CYP)4F2 gene is known to influence mean coumarin dose. The aim of the present study was to undertake a meta-analysis at the individual patients level to capture the possible effect of ethnicity, gene-gene interaction, or other drugs on the association and to verify if inclusion of CYP4F2*3 variant into dosing algorithms improves the prediction of mean coumarin dose. We asked the authors of our previous meta-analysis (30 articles) and of 38 new articles retrieved by a systematic review to send us individual patients' data. The final collection consists of 15,754 patients split into a derivation and validation cohort. The CYP4F2*3 polymorphism was consistently associated with an increase in mean coumarin dose (+9% (95% confidence interval (CI) 7-10%), with a higher effect in women, in patients taking acenocoumarol, and in white patients. The inclusion of the CYP4F2*3 in dosing algorithms slightly improved the prediction of stable coumarin dose. New pharmacogenetic equations potentially useful for clinical practice were derived.

Immunophenotypic Characteristics of T-Acute Lymphoblastic Leukemia in Omani Patients: A Correlation with Demographic Factors.

OBJECTIVES: To study and classify the immunophenotypic characteristics of Omani patients diagnosed with T-cell acute lymphoblastic leukemia (T-ALL) and to correlate the results with age and gender as well as biological factors (peripheral and bone marrow blast cells percentage). METHODS: Fifty cases from both genders and of all ages who fulfilled the inclusion criteria with a diagnosis of T-ALL were included in the study. Correlation of T-ALL subtypes with age, gender, and initial bone marrow and peripheral blood blast cells percentage was assessed using ANOVA. RESULTS: Among the 50 T-ALL patients analyzed, 44 were male and six were female giving a male-to-female ratio of 7:1 (p = 0.007). The average age of patients was 19.2 years with no significant differences in the three disease subtypes. No significant association was seen between the peripheral or bone marrow blast cell percentage and the differentiation stages of the neoplastic clone of T-ALL. All female patients were found to express an immature T-ALL phenotype. CONCLUSIONS: This study reports the subtypes of T-ALL in Oman for the first time. It is hoped that this will lead to a better understanding of the disease outcomes.

Regulatory B Cells Are Functionally Impaired in Patients Having Hemophilia A With Inhibitors.

Development of inhibitors remains a major clinical complication in patients with hemophilia A receiving replacement therapy with factor VIII (FVIII). Understanding the immune mechanisms involved in the development of inhibitors can provide valuable information about pathways to human tolerance. Recent evidence indicates that B regulatory (Breg) cells play a pivotal role in controlling the production of antibodies (Abs) while promoting follicular T helper (Tfh) cells and monocytes, expressing the low-density lipoprotein receptor-related protein (LRP/CD91), which is involved in FVIII intake from the circulation. We studied circulating levels of Breg cells along with Tfh cells and the expression of LRP/CD91 on monocytes in patients with hemophilia A using 8-color flow cytometry and cell culture. Compared to healthy controls, patients with hemophilia A with inhibitors showed a severe reduction in levels of Breg cells and produced less interleukin-10 when activated via the CD40 signaling pathway. In addition, patients with hemophilia A with inhibitors exhibited an overexpression of LPR/CD91 on monocytes and normal levels of Tfh cells. Levels of Breg cells were not significantly related to LPR/CD91 although negative associations were evidenced. Collectively, these results provide new insights into the role of Breg cells and LPR/CD91 in the development of inhibitors in patients with hemophilia A.

Portal Vein Thrombosis in Adult Omani Patients: A Retrospective Cohort Study.

OBJECTIVES: We sought to study the occurrence of portal vein thrombosis (PVT) in adult Omani patients. Methods: We conducted a retrospective cross-sectional study in patients diagnosed with PVT, which was confirmed by radiological imaging, from two tertiary hospitals over a 10-year period. Results: Amongst the 39 patients enrolled in the study, 15 (38.4%) had cirrhosis of the liver, and 24 (61.5%) were non-cirrhotic. In the non-cirrhotic PVT patients, 15 (62.5%) had acute PVT, whereas nine (37.5%) had chronic PVT. PVT was more common in males than females, (25 (64.1%) vs. 14 (35.8%), respectively, p = 0.020). The three most common clinical symptoms were abdominal pain (n = 25, 64.1%) followed by nausea (n = 12, 30.7%) and fever (n = 8, 20.5%) patients. Causative risk factors included prothrombotic states (17.9-28.2%) and local factors (20.5%) such as cholecystitis, cholangitis, and liver abscess. Complications were found in 23.0% of patients with PVT, namely variceal bleeding in seven patients (17.9%) patients and bowel ischemia in two patients (5.1%). Management with sclerotherapy was performed in all patients with variceal bleeding. Thrombectomy was done for one patient complicated with intestinal ischemia, but as it failed, he was treated with warfarin anticoagulation. CONCLUSIONS: This is the first study reflecting a real-life practice in PVT with possibly underlying inherited and acquired prothrombotic conditions as well as complications due to local and malignant conditions from Oman. We studied the prevalence, clinical presentation, underlying possible etiological factors, treatment, and outcomes. Since causative factors were found in 36 patients (92.3%), etiological screening seems worthwhile in every case with PVT, but thrombophilia screening may not be cost-effective.

First Cytogenetic Profile of Omani Patients with de novo Myelodysplastic Syndromes: Comparison with data from Asia, Africa, Europe and North and South America.

Clonal cytogenetic abnormalities have been reported among 30-80% of patients with myelodysplastic syndromes (MDS); however, 20-70% of patients with MDS show a normal karyotype that may nevertheless harbour a cryptic genetic alteration. Earlier reports have suggested that the distribution of specific chromosomal aberrations varies among Western and Asian countries, with geographical and ethnic differences in the frequency of specific chromosomal aberrations. This article compared the cytogenetic data of 36 adult Omani patients with MDS to previously reported data from other populations. Differences were noted between the percentages of clonal aberrations and the median age of Omani subjects at presentation in comparison to individuals of different ethnicities and from various geographical locations. To the best of the authors' knowledge, this is the first report to describe the cytogenetic data of patients with MDS from Oman.

Impact of Educational Activities in Reducing Pre-Analytical Laboratory Errors: A quality initiative.

OBJECTIVES: Pre-analytic errors during diagnostic laboratory investigations can lead to increased patient morbidity and mortality. This study aimed to ascertain the effect of educational nursing activities on the incidence of pre-analytical errors resulting in non-conforming blood samples. METHODS: This study was conducted between January 2008 and December 2015. All specimens received at the Haematology Laboratory of the Sultan Qaboos University Hospital, Muscat, Oman, during this period were prospectively collected and analysed. Similar data from 2007 were collected retrospectively and used as a baseline for comparison. Non-conforming samples were defined as either clotted samples, haemolysed samples, use of the wrong anticoagulant, insufficient quantities of blood collected, incorrect/lack of labelling on a sample or lack of delivery of a sample in spite of a sample request. From 2008 onwards, multiple educational training activities directed at the hospital nursing staff and nursing students primarily responsible for blood collection were implemented on a regular basis. RESULTS: After initiating corrective measures in 2008, a progressive reduction in the percentage of non-conforming samples was observed from 2009 onwards. Despite a 127.84% increase in the total number of specimens received, there was a significant reduction in non-conforming samples from 0.29% in 2007 to 0.07% in 2015, resulting in an improvement of 75.86% (P <0.050). In particular, specimen identification errors decreased by 0.056%, with a 96.55% improvement. CONCLUSION: Targeted educational activities directed primarily towards hospital nursing staff had a positive impact on the quality of laboratory specimens by significantly reducing pre-analytical errors.

Alloimmunization in Patients with Sickle Cell Disease and Thalassemia: Experience of a Single Centre in Oman.

BACKGROUND: Blood transfusion is an integral part of the supportive care for patients with sickle cell disease (SCD) and thalassaemia. The hazard of red cell alloimmunization, however, is one of the main complications of this therapy. OBJECTIVES: The aim of this study was to evaluate the prevalence of red cell alloimmunization in Omani patients with sickle cell anaemia and thalassemia. METHODS: This study included 262 patients whose historical transfusion records were available. One hundred and twenty-nine patients with thalassaemia who were attending the day care unit for regular transfusions, and 133 SCD patients admitted at our hospital were included in this study. The Diamed® gel system was used for the screening and identification of atypical antibodies. RESULTS: The rate of alloimmunization in SCD patients was 31.6% (n=42, 95%CI, 24.87-40.66), whereas in patients with thalassaemia it was 20% (n=26; 95%CI, 13.9-27.6). Antibodies to E, e, C, c, D, K, S, Fyª, Kpª, Jkª and Cw were observed; 85% of the patients were also immunised with Rh and Kell antigens. Considering the two groups together, 8 developed nonspecific antibodies and 12 developed more than one antibody. CONCLUSIONS: Red cell transfusions were associated with a significant risk of alloimmunization. It is, therefore, imperative to perform an initial extended red cell phenotyping for both donors and recipients, and carefully select ABO, Rh and Kell matched donors. The higher incidence of alloimmunization in SCD patients is related to the inherent SCD-specific inflammatory state.