Prognostic factors of disease severity in infants with sickle cell anemia: A comprehensive longitudinal cohort study

A novel red blood cell deformability biomarker is associated with hemolysis and vaso-occlusive crises in sickle cell disease

Sickle cell disease (SCD) is among the most prevalent genetic disorders worldwide. It is characterized by unpredictable and potentially fatal vaso-occlusive crises, directly linked to the stiffening of red blood cells (RBCs) due to the formation of hemoglobin fibers in their cytoplasm. Here, we propose a new mechanical marker: the proportion of RBCs in a blood sample deformable enough to exhibit a specific tank-treading motion, in shear flow at a given shear rate. This marker is significantly lower in SCD patients than in controls and is sensitive to RBC density and dehydration, two factors that influence hemoglobin polymerization in SCD. The marker was tested in a cohort of 21 SCD patients, with weekly monitoring conducted over a period of 6 months. It correlates with key biological parameters of SCD including fetal hemoglobin levels, reticulocyte count, serum LDH levels, and the use of antihypertensive treatments. The marker significantly decreases before vaso-occlusive crises requiring hospitalization. These findings indicate that this marker may act as a comprehensive indicator of RBC deformability, offering valuable insights for the continuous clinical monitoring of SCD patients. It could play a role in managing or preventing vaso-occlusive crises and holds potential for the development of new diagnostic tests such as point-of-care or companion diagnostic devices for personalized medicine.

Selecting patients with sickle cell disease for gene addition or gene editing-based therapeutic approaches: Report on behalf of a joint EHA Specialized Working Group and EBMT Hemoglobinopathies Working Party consensus conference

Sickle cell disease (SCD) remains associated with reduced life expectancy and poor quality of life despite improvements observed in the last decades mostly related to comprehensive care, use of hydroxycarbamide, screening to identify patients at risk of strokes, and implementation of safe transfusion protocols. The course of the disease is highly variable, making it difficult to predict severity and response to therapy. Allogeneic hematopoietic stem cell transplantation potentially provides a cure with a relatively low rate of complications, but few patients have an HLA-identical sibling. The hopes of patients and healthcare providers have been raised after the initial excellent results of gene therapy studies. However, there is a strong contrast between the high expectations of families and patients and the limited availability of the product, which is technically complex and very expensive. In light of this consideration and of the limited data available on the long-term efficacy and toxicity of different gene therapy approaches, the European Hematology Association Red Cell & Iron Specialized Working Group (EHA SWG) and the hemoglobinopathy working part of the European Blood & Marrow Transplant (EBMT) Group have prioritized the development of recommendations for selection of patients with SCD who are good candidates for gene therapy. The decision-making algorithm was developed by a panel of experts in hemoglobinopathies and/or transplantation chosen by EHA SWG and EBMT, to discuss the selection of SCD patients for gene therapy and draw notes on the related clinical problems.

Oxygen gradient ektacytometry-derived biomarkers are associated with acute complications in sickle cell disease

ABSTRACT

We investigated the potential of the point of sickling (PoS; the pO2 tension at which red cells start to sickle), determined by oxygen gradient ektacytometry to serve as a biomarker associated with the incidence of acute sickle cell disease-related complications in 177 children and 50 adults. In the pediatric cohort, for every 10 mmHg increase in PoS reflecting a greater likelihood of sickling, the likelihood of an individual experiencing >1 type of acute complication increased; the adjusted odds ratio (aOR) was 1.65. For every 0.1 increase in minimum elongation index (EImin; reflecting improved red blood cell deformability at hypoxia), the aOR was 0.50. In the adult cohort, for every 10 mmHg increase in PoS, we found an aOR of 3.00, although this was not significant after correcting for multiple testing. There was a trend for an association between higher PoS and greater likelihood of vaso-occlusive episodes (VOEs; children aOR, 1.35; adults aOR, 2.22). In children, only EImin was associated with VOEs (aOR, 0.68). When data of both cohorts were pooled, significant associations with PoS and/or EImin were found for all acute complications, independently and when >1 type of acute complication was assessed. These findings indicate that oxygen gradient ektacytometry generates novel biomarkers and provides a rationale for further development of these biomarkers in the assessment of clinical severity, evaluation of novel therapies, and as surrogate clinical trial end points. These biomarkers may be useful in assessing efficacy of novel therapies like pyruvate kinase activators, voxelotor, and L-glutamine.

Genetic literacy and experiential knowledge on sickle cell disease among Canadian- and foreign-born male and female Anglophone and Francophone youth in Canada

OBJECTIVES

Growing global human mobility raises concerns about impacts on global health, particularly on the prevalence of sickle cell disease. This research unveiled the level of genetic literacy on sickle cell disease of male and female Anglophone and Francophone youth living in Canada. The research responded to questions about whether the type of information about the disease has been more prevalent among the youth's family, friends, acquaintances and school circles, and the influence of such information on shaping the current youth level of genetic literacy on the disease.

METHODS

An online survey hosted by a Canadian university (2019/2020) platform was conducted with youth (n=87, aged 16-29) recruited in their natural, social environments in seven Canadian provinces. Data analysis used descriptive statistics and manual qualitative content analysis.

RESULTS

Youth, mostly Canadian-born, 71.42 % Francophones and 67.12 % Anglophones, descend from parents who had been born in countries at risk for the disease. Results indicated that experiential knowledge is due to the familiarity with the disease occurrence among family members and acquaintances. Participants did not comment about how academic-gained knowledge could influence their own decision on becoming a parent.

CONCLUSIONS

Independently of their country of birth, Canadian youth seem to have unmet information needs: a complex challenge requiring creativity and simplicity to deliver information through attractive media.

[Splenic dysfunction in sickle cell disease: An update]

The spleen filters blood cells and contributes to the immune defense. The red pulp clears the blood from altered red blood cells via its unique microcirculatory network ; while the white pulp is a secondary lymphoid organ, directly connected to the bloodstream, whose specificity is the defense against encapsulated bacteria through the production of "natural" IgM in the marginal zone. Various health conditions can cause acquired impairment of the splenic function (or hyposplenism) directly and/or through therapeutic splenectomy. Hypo/asplenia is complicated by an increased susceptibility to encapsulated germ infections, but an increased risk of thrombosis and pulmonary hypertension has also been reported after surgical splenectomy. Homozygous sickle cell disease is the most common disease associated with functional asplenia. The latter appears early in childhood likely through repeated ischemic alterations caused by the sickling of red blood cells. In addition, specific complications such as hypersplenism and acute splenic sequestration can occur and may be life-threatening. We provide here an update on the role and physiology of the spleen, which will allow a better understanding of the pathophysiology of spleen damage and its consequences in sickle cell disease.

Precision Medicine and Sickle Cell Disease

Sickle cell disease (SCD) is characterized by variable clinical outcomes, with some patients suffering life-threatening complications during childhood, and others living relatively symptom-free into old age. Because of this variability, there is an important potential role for precision medicine, in which particular different treatments are selected for different groups of patients. However, the application of precision medicine in SCD is limited by difficulties in identifying different prognostic groups and the small number of available treatments. The main genetic determinant of outcomes in SCD is the underlying β-globin genotype, with sickle cell anemia (HbSS) and hemoglobin SC disease (HbSC) forming the 2 major forms of the disease in most populations of African origin. Although there are clear differences in clinical outcomes between these conditions, treatments approaches are very similar, with little evidence on how to treat HbSC in particular. Other genomic information, such as the co-inheritance of α-thalassemia, or high fetal hemoglobin (HbF) levels, is of some prognostic value but insufficient to determine treatments. Precision medicine is further limited by the fact that the 2 main drugs used in SCD, penicillin and hydroxyurea, are currently recommended for all patients. Newer treatments, such as crizanlizumab and voxelotor, raise the possibility that groups will emerge who respond best to particular drugs or combinations. Perhaps the best current example of precision medicine in SCD is the selective use of blood transfusions as primary stroke prevention in children with evidence of cerebral vasculopathy. More precise treatments may emerge as we understand more about the pathology of SCD, including problems with erythropoiesis.

Determinants of severity in sickle cell disease

Sickle cell disease is a very variable condition, with outcomes ranging from death in childhood to living relatively symptom free into the 8^th decade. Much of this variability is unexplained. The co-inheritance of α thalassaemia and factors determining HbF levels significantly modify the phenotype, but few other significant genetic variants have been identified, despite extensive studies. Environmental factors are undoubtedly important, with socio-economics and access to basic medical care explaining the huge differences in outcomes between many low- and high-income countries. Exposure to cold and windy weather seems to precipitate acute complications in many people, although these effects are unpredictable and vary with geography. Many studies have tried to identify prognostic factors which can be used to predict outcomes, particularly when applied in infancy. Overall, low haemoglobin, low haemoglobin F percentage and high reticulocytes in childhood are associated with worse outcomes, although again these effects are fairly weak and inconsistent.

The ektacytometric elongation Index (EI) of erythrocytes, validation of a prognostic, rheological biomarker for patients with sickle cell disease

OBJECTIVES

Validation of the measurement of erythrocyte deformability as a useful prognostic, rheological biomarker for patients with sickle cell disease (SCD).

METHODS

The degree of reduced deformability was based on the value of the maximum elongation index (EI_max ) of the deformability curve of an osmotic gradient ektacytometer. The performance of this technique was analytically and clinically validated by analysing 200 normal subjects and 100 patients with well-documented thalassemia's and Hb variants in relation to their clinical condition.

RESULTS

In this study, we show that EI_max is a reproducible parameter with a small inter-individual coefficient of (Biological) variation (CV)=1.6% and a small intra-individual CV=3.5%. We demonstrate that loss of deformability correlates with the clinical condition and the various mutations underlying sickle cell disease and thalassemia. For SCD patients, a strongly reduced EI_max with a cut-off =0.360 is a signal for future vaso-occlusive (VOC) events requiring hospitalisation with a specificity=85%, sensitivity=80%, PPV=81% and NPV=84% based on a ROC curve (AUC=0.89).

CONCLUSION

This study validated the clinical utility of EI_max as a prognostic marker for future clinical problems in individual high-risk SCD patients. In addition, EI_max may help to achieve an adequate personal transfusion policy for an optimal blood flow in anaemic patients with SCD.

Age of first pain crisis and associated complications in the CASiRe international sickle cell disease cohort

Pain is a hallmark of Sickle Cell Disease (SCD) affecting patients throughout their life; the first pain crisis may occur at any age and is often the first presentation of the disease. Universal newborn screening identifies children with SCD at birth, significantly improving morbidity and mortality. Without early screening, diagnosis is generally made after disease manifestations appear. The Consortium for the Advancement of Sickle Cell Research (CASiRe) is an international collaborative group evaluating the clinical severity of subjects with SCD using a validated questionnaire and medical chart review, standardized across 4 countries (United States, United Kingdom, Italy and Ghana). We investigated the age of first pain crisis in 555 sickle cell subjects, 344 adults and 211 children. Median age of the first crisis in the whole group was 4 years old, 5 years old among adults and 2 years old among children. Patients from the United States generally reported the first crisis earlier than Ghanaians. Experiencing the first pain crisis early in life correlated with the genotype and disease severity. Early recognition of the first pain crisis could be useful to guide counseling and management of the disease.

Fetal hemoglobin in sickle cell anemia

Fetal hemoglobin (HbF) can blunt the pathophysiology, temper the clinical course, and offer prospects for curative therapy of sickle cell disease. This review focuses on (1) HbF quantitative trait loci and the geography of β-globin gene haplotypes, especially those found in the Middle East; (2) how HbF might differentially impact the pathophysiology and many subphenotypes of sickle cell disease; (3) clinical implications of person-to-person variation in the distribution of HbF among HbF-containing erythrocytes; and (4) reactivation of HbF gene expression using both pharmacologic and cell-based therapeutic approaches. A confluence of detailed understanding of the molecular basis of HbF gene expression, coupled with the ability to precisely target by genomic editing most areas of the genome, is producing important preliminary therapeutic results that could provide new options for cell-based therapeutics with curative intent.

Insights into determinants of spleen injury in sickle cell anemia

Spleen dysfunction is central to morbidity and mortality in children with sickle cell anemia (SCA). The initiation and determinants of spleen injury, including acute splenic sequestration (ASS) have not been established. We investigated splenic function longitudinally in a cohort of 57 infants with SCA enrolled at 3 to 6 months of age and followed up to 24 months of age and explored the respective contribution of decreased red blood cell (RBC) deformability and increased RBC adhesion on splenic injury, including ASS. Spleen function was evaluated by sequential ^99mTc heated RBC spleen scintigraphy and high-throughput quantification of RBCs with Howell-Jolly bodies (HJBs). At 6 and 18 months of age, spleen filtration function was decreased in 32% and 50% of infants, respectively, whereas the median %HJB-RBCs rose significantly (from 0.3% to 0.74%). An excellent correlation was established between %HJB-RBCs and spleen scintigraphy results. RBC adhesion to laminin and endothelial cells increased with time. Adhesion to endothelial cells negatively correlated with splenic function. Irreversibly sickled cells (ISCs), used as a surrogate marker of impaired deformability, were detected at enrollment and increased significantly at 18 months. %ISCs correlated positively with %HJB-RBCs and negatively with splenic uptake, indicating a relationship between their presence in the circulation and spleen dysfunction. In the subgroup of 8 infants who subsequently experienced ASS, %ISCs at enrollment were significantly higher compared with the asymptomatic group, suggesting a major role of impaired deformability in ASS. Higher levels of %HJB-RBCs were observed after the occurrence of ASS, demonstrating its negative impact on splenic function.

HbS/β+ thalassemia: Really a mild disease? A National survey from the AIEOP Sickle Cell Disease Study Group with genotype-phenotype correlation

OBJECTIVES

HbS/β+ patients' presence in Italy increased due to immigration; these patients are clinically heterogeneous, and specific guidelines are lacking. Our aim is to describe a cohort of HbS/β+ patients, with genotype-phenotype correlation, in order to offer guidance for clinical management of such patients.

METHODS

Retrospective cohort study of HbS/β+ patients among 15 AIEOP Centres.

RESULTS

A total of 41 molecularly confirmed S/β+ patients were enrolled (1-55 years, median 10.9) and classified on β+ mutation: IVS-I-110, IVS-I-6, promoter, and "others." Prediagnostic events included VOC 16/41 (39%), ACS 6/41 (14.6%), sepsis 3/41 (3.7%), and avascular necrosis 3/41 (7,3%). Postdiagnostic events were VOC 22/41 (53.6% %), sepsis 4/41 (9.7%), ACS 4/41 (9.7%), avascular necrosis 3/41 (7.3%), aplastic crisis 2/41 (4.8%), stroke 1/41 (2.4%), ACS 1/41 (2.4%), and skin ulcerations 1/41 (2.4%). The IVS-I-110 group presented the lowest median age at first SCD-related event (P = .02 vs promoter group) and the higher median number of severe events/year (0.26 events/patient/year) (P = .01 vs IVS-I-6 and promoter groups). Promoter group presented a specific skeletal phenotype. Treatment regimen applied was variable among the centers.

CONCLUSIONS

HbS/β+ is not always a mild disease. Patients with IVS-I-110 mutation could benefit from a standard of care like SS and S/β° patients. Standardization of treatment is needed.

Prevalence and predictive factors of splenic sequestration crisis among 423 pediatric patients with sickle cell disease in Tunisia

This study was aimed to identify the predictors of splenic sequestration crisis (SSC) among pediatric patients with sickle cell disease (SCD). This prognosis study was carried out in the pediatric immuno-hematology unit, over 20 years (1998 to 2017), enrolling patients with SCD. The cox model was used in multivariate analysis. Among 423 patients with SCD (240 S/S phenotype, 128 S/B0, 30 S/B+, 14 S/O arab and 11 S/C), 150(35.4%) had at least one episode of SSC. The average age of patients at the first episode was 48.3 months ± 32.4(2-168). Recurrence of SSC was observed in 117 patients (78%). Spleen size ≥3 cm at baseline was the strongest predictor of SSC occurrence (HR = 7.27, CI: 4.01-13.20, p = 0.05) and recurrence (HR = 6.37, CI: 1,46-27.83, p = 0.01). Pallor revealing the disease, age at onset of symptoms <24 months and reticulocytosis ≥300,000/mm³ increased the risk of SSC. Pain crisis revealing the disease as well as neutrophilia was associated with a lower risk of SSC. In conclusion, this study confirmed the high prevalence of SSC in SCD and the high frequency of recurrence after a first episode. The SSC occurrence and recurrence were intimately linked to the presence of splenomegaly, chronic pallor revealing the disease as well as reticulocytosis.

Considering the spleen in sickle cell disease

Introduction: In human physiology, the spleen is generally neglected, and its role is considered anecdotal. In sickle cell disease, splenic dysfunction is the main cause of life-threatening complications, particularly in early childhood with the risk of pneumococcal overwhelming sepsis and acute splenic sequestration crisis, notably. During the course of the disease, the spleen functionally declines and anatomically disappears, albeit with great individual variability depending on modulating genetic and environmental factors. Areas covered: The present review aims to provide an overview of spleen structure and function in order to highlight its role in sickling disorders. The clinical features of spleen damage in sickle cell disease, as well as complications and short- and long-term consequences, are reviewed, along with the main therapeutic options. Expert opinion: Management of acute splenic sequestration recurrence and timing of splenectomy in children with sickling disorders are two main areas in which clinical studies are needed.

Association of fetal hemoglobin level with frequency of acute pain episodes in sickle cell disease (HbS-only phenotype) patients

BACKGROUND

Sickle cell disease (SCD) is a Mendelian single gene disorder with highly variable phenotypic expression. In the present study, we analyzed the influence of HbF, alpha thalassemia and other hematological indices to determine their association with acute pain episodes.

METHOD

This case control study consisted of SCD subjects with HbS phenotype experiencing three or more acute pain episodes in last twelve months (cases) and without any episode of acute pain during last twelve months (controls). Hematological parameters, HbF, and presence of alpha thalassemia were assessed in all subjects.

RESULTS

A statistically significant difference between HbF levels (P < 0.025, χ2 test) and alpha thalassemia (P < 0.008, χ2 test) was observed between controls and cases group. Univariate analysis indicated that increased HbF levels > 25% (OR: 0.37, 95% CI: 0.18-0.77, P < 0.008) and presence of alpha thalassemia (OR: 0.53, 95% CI: 0.33-0.85, P < 0.009) provided protection, while multivariate analysis revealed significant protection was attributable only by higher HbF levels (OR: 0.39, 95% CI: 0.17-0.88, P < 0.025). Significantly higher HbF levels were observed only in the 11-20 age group of cases in comparison to controls (Student's t-test, P < 0.001).

CONCLUSION

Higher concentrations of HbF are associated with protection against frequent episodes of acute pain crisis in SCD patients.