Cardiovascular complications of sickle cell disease

Cardiovascular Anesthesia and Critical Care in the French West Indies: Historical Evolution and Current Prospects

Anesthesiology, the medical specialty that deals with the management of vital functions in patients undergoing surgery, has played an important role in the successful development of cardiac interventions worldwide. Tracing the historical roots of cardiac anesthesia and critical care from its inception in the late 1950s, a paradigm shift in perioperative care has been driven by a better understanding of the mechanisms of organ dysfunction in stressful conditions and technological advances regarding surgical approach, patient monitoring, and organ protection. Although progress in cardiac anesthesia and critical care lagged a little behind in Caribbean territories, successful achievements have been accomplished over the last forty years. Compared with Western countries, the greater prevalence of obesity, diabetes mellitus, and hypertension as well as specific diseases such as cardiac amyloidosis, sickle cell anemia, rheumatic heart disease, and tropical infections may reduce a patient's physiologic reserve and increase the operative risk among the multi-ethnic population living in the French West Indies and Guiana. So far, cardiac anesthesiologists at the University Hospital of Martinique have demonstrated their abilities in implementing evidence-based clinical care processes and adaptating to efficiently working in a complex environment interacting with multiple partners. Attracting specialized physicians in dedicated cardiac surgical centers and the creation of a regional health network supported by governmental authorities, insurance companies, and charitable organizations are necessary to solve the unmet needs for invasive cardiac treatments in the Caribbean region.

Prevent Acute Chest Syndrome checklist (PACScheck): A quality improvement initiative to reduce acute chest syndrome

BACKGROUND

Acute chest syndrome (ACS) is a life-threatening complication of sickle cell disease (SCD). The Prevent Acute Chest Syndrome checklist (PACScheck) was created to drive appropriate ordering of opioids, incentive spirometry (IS), intravenous fluids (IVF), evaluation of oxygen desaturation, and bronchodilator use.

OBJECTIVES

Decrease the development of ACS by 5% in a hospitalized pediatric SCD population.

METHODS

A multidisciplinary team conducted a quality improvement (QI) project between April 2020 and August 2021 on an inpatient pediatric hematology unit. At-risk hospitalizations were patients with SCD who did not have ACS upon hospital admission. PACScheck was implemented and weekly run charts assessed documentation. Process control (p) charts, geometric control (g) charts, and chi-square tests assessed checklist process measures pre- and post-PACScheck. G chart assessed the number of encounters between ACS events.

RESULTS

A total of 483 at-risk hospitalizations were identified in the 12 months prior and 363 during the study period. A g chart demonstrated that fewer encounters developed ACS during PACScheck. A p chart demonstrated that IS documentation increased during PACScheck. A run chart of PACScheck documentation demonstrated a median of 100% documentation at least once per hospitalization during the last six months of the intervention.

CONCLUSION

Development of ACS can be reduced by implementing a best-practices checklist (PACScheck) on an inpatient pediatric hematology unit with a multidisciplinary team.

Sickle cell trait in non-firearm arrest-related deaths of Black persons

The role of sickle cell trait (SCT) in sudden exertional death is well-recognized in sports and military training. However, it is not yet studied for non-firearm arrest-related death (NF-ARD). With extensive multi-pronged searches, a large database (n = 1389) of NF-ARDs was established. For the years 2006-2021 (inclusive) there were 50 NF-ARDs of Black persons in which postmortem evidence of SCT was found. A control cohort consisted of 414 NF-ARDs of Black persons with no reported SCT. The mean age for SCT cases was 33.1 ± 10.4 years versus 37.0 ± 10.4 years for the control group (p = 0.01). The body-mass index for SCT cases was 28.3 ± 6.6 kg/m2 versus 30.7 ± 7.6 kg/m2 for the control group (p = 0.03). The prevalence of cardiomegaly was 21% for SCT cases versus 39% in the control cohort (p = 0.008). The postmortem prevalence of SCT in NF-ARDs of Black persons (n = 50, 10.7%) was higher than the prevalence of SCT in the US Black population, which is 7.1% (p = 0.003). In this study of NF-ARDs in Black persons, the prevalence of SCT and the differences between the SCT cases and the control cohort suggest that exertional collapse associated with sickle cell trait may be a contributory factor in NF-ARDs.

Clinical Insights into Sickle Cell Disease: A Comprehensive Multicenter Retrospective Analysis of Clinical Characteristics and Outcomes Across Different Age Groups

Background: Sickle cell disease (SCD) is a genetic hematological disorder associated with significant mortality and a range of complex complications that manifest differently across various age groups. Methods: This study aimed to evaluate the demographic, clinical, and laboratory characteristics of SCD patients in Taif City, Saudi Arabia, with a focus on variations among children, adolescents, adults, and middle-aged individuals. A multicenter retrospective cohort study included 129 patients with confirmed diagnosis of SCD between January 2018 to October 2023 and divided into 4 cohorts. The analysis compared hospital stay durations, admission rates, SCD complications, and medication usage. Results: Among the participants, 35 were children (27%), 18 adolescents (14%), 63 adults (49%), and 13 middle-aged individuals (10%). Clinical complications as splenic disease in children (34.3%) were more frequent compared to adolescents (5.6%) and adults (4.8%). Additionally, chronic kidney disease was more prevalent in middle-aged patients (15.4%). Pain was reported in 65.1% of patients, with vascular occlusive crises occurring in 41.1%. Treatment adherence varied, with children showing higher penicillin use (74.3%), while opioid usage was greater in middle-aged patients (76.9%). Conclusions: The findings underscore the necessity for age-specific management strategies in SCD. Further research with larger populations is suggested to enhance the understanding of disease progression and treatment efficacy across different age groups.

Prevalence of metabolic syndrome in sickle cell disease patients: A cross-sectional study at a tertiary hospital in Nepal

Background

Sickle cell disease (SCD) is the most common hemoglobinopathy caused by an autosomal recessive genetic disorder leading to increased morbidity and mortality rates. SCD is prevalent in the Tharu community in the lowland (Terai) region of Nepal. Prevalence of metabolic syndrome among adults with SCD is poorly studied.

Methodology

This prospective cross-sectional study was conducted at Seti Provincial Hospital in Dhangadhi, Nepal, among 140 adolescents and adults with SCD, aged 15-60 years. Anthropometric and laboratory data were collected using an assisted questionnaire, and the SPSS software version 23 was used for data analysis. Descriptive and inferential statistics were used to summarize the presence of metabolic syndrome and were stratified in separate analyses by age and sex. National Cholesterol Education Program-Adult Treatment Panel III criteria were used to define metabolic syndrome.

Aim

This cross-sectional study aimed to assess the prevalence of metabolic syndrome among SCD patients with SCD registered at the Seti Provincial Hospital in Dhangadhi, Nepal.

Results

The prevalence of metabolic syndrome in the study participants was 7.8%. Our study revealed 5% of the patients overweight, and 1.4% obese. In this study, the mean triglyceride level was 118.5 mg/dL, and the mean high-density lipoprotein (HDL) level was 36.2 mg/dL (men) and 36.7 mg/dL (women). This study found that the mean fasting blood glucose level was 88.6 gm/dL. Similarly, 3.5% of patients had increased systolic blood pressure, and 7.8% had raised diastolic blood pressure. Study shows that changes in triglyceride level (p = 0.013), waist circumference, and HDL level (p = 0.0001 and 0.0048, respectively) are significantly associated with smoking or alcohol consumption; however, change in blood pressure (p = 0.013) and fasting blood sugar level (p = 0.086) are not associated with smoking or alcohol consumption.

Conclusion

Study concluded that though a lower proportion of SCD patients met the criteria for metabolic syndrome than in studies conducted in developed countries, it is crucial to consider metabolic syndrome while managing patients with SCD. Nevertheless, the authors advocate a more comprehensive study to draw significant conclusions.

Clinical Outcomes of Sickle Cell Disease Patients With Myocardial Infarction Undergoing Percutaneous Coronary Intervention: A Nationwide Analysis

Sickle cell disease (SCD) patients are predisposed to various cardiovascular complications due to the nature and progression of the disease; the clinical outcomes of SCD patients experiencing myocardial infarction (MI) and undergoing percutaneous coronary intervention (PCI) are not well known. This study aims to explore a comprehensive nationwide analysis of the clinical outcomes in SCD patients who have suffered an MI and subsequently undergone PCI. It also identifies potential complications and compares their outcomes with non-SCD counterparts with the same interventions. We conducted a retrospective analysis of SCD patients who have suffered an MI and subsequently undergone PCI using the National Inpatient Sample (NIS) database from 2016 to 2020. The primary outcome was mortality, while the secondary outcomes were the average length of stay, comorbid conditions, and cardiovascular outcomes. Logistic, linear, and Poisson regression model analysis applied for outcomes and adjusting co-founders. P-value <0.05 was considered significant. A total of 775 patients were analyzed for MI who had PCI with SCD, with a mean age of 58±1.06 years. SCD patients exhibited higher rates of comorbidities, including diabetes mellitus (45.81% vs. 37.84%), obesity (23.87% vs. 20.85%), and chronic kidney disease (CKD) (29.03% vs. 17.36%). Heart failure was more common among SCD patients with 34.19% vs. 26.02% in non-SCD patients (OR 1.5, CI 1.1-2.1, p-value=0.02). Other cardiovascular complications such as stroke, ventricular arrhythmias, atrial fibrillation, pulmonary edema, cardiogenic shock, cardiac arrest, and mortality did not significantly differ between SCD and non-SCD (P-values >0.05). The study observed that SCD patients experienced a significantly higher incidence of heart failure than non-SCD patients. This implies that SCD patients undergoing PCI for MI exhibit distinct clinical outcomes compared to their non-SCD counterparts.

Proliferative Sickle Cell Retinopathy: Outcomes of Vitreoretinal Surgery

PURPOSE

To report the clinical presentation and outcomes in patients who underwent surgery for proliferative sickle cell retinopathy (PSCR).

DESIGN

Retrospective, consecutive case series.

SUBJECTS

All patients who underwent vitreoretinal surgery for complications secondary to PSCR between January 1, 2014, and December 31, 2021, at a university referral center.

METHODS

Retrospective consecutive case series.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA), single operation anatomic success rate.

RESULTS

The study included 65 eyes of 61 patients. Disease distribution included 24 (44.4%) eyes with hemoglobin SC disease, 14 (25.9%) with hemoglobin SS disease, 13 (24.1%) with sickle cell trait, and 3 (5.6%) with sickle cell-β thalassemia. Preoperative transfusion was not performed in any study patients. Regional anesthesia with monitored anesthesia care (RA-MAC) was utilized in 58 (89.2%) eyes and general anesthesia in 7 (10.8%). In eyes that underwent surgery for retinal detachment (RD; N = 52) the rate of single operation anatomic success was 72.4% with combined scleral buckling/pars plana vitrectomy (SB/PPV; N = 29) compared with 47.8% with PPV alone (N = 23; P = 0.07). Mean BCVA at the last follow-up examination was 1.27 (20/372) in the SB/PPV group and 1.05 (20/226) in the PPV group (P = 0.48). In all SB cases, an encircling band was utilized and there were no known cases of anterior segment ischemia. All eyes that had surgery for vitreous hemorrhage (N = 13) underwent PPV with endolaser and mean BCVA improved from 1.67 (20/944) preoperatively to 0.45 (20/56) at last follow-up examination (P < 0.001). Mean preoperative BCVA, indication for surgery, single operation success rate, and mean BCVA at last follow-up examination did not differ based on sickle cell disease type (P > 0.05).

CONCLUSIONS

In patients with RD, SB/PPV achieved slightly higher rates of single operation anatomic success compared with PPV alone. Visual acuity outcomes were similar in the 2 groups. The majority of patients received RA-MAC anesthesia and preoperative transfusions were not performed. There were no cases of postoperative anterior segment ischemia. Hemoglobin SC disease was the most common disease type in the current study and surgical outcomes did not differ between sickle cell disease types.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Impacts of oxidative stress and anti-oxidants on the development, pathogenesis, and therapy of sickle cell disease: A comprehensive review

Sickle cell disease (SCD) is the most severe monogenic hemoglobinopathy caused by a single genetic mutation that leads to repeated polymerization and depolymerization of hemoglobin resulting in intravascular hemolysis, cell adhesion, vascular occlusion, and ischemia-reperfusion injury. Hemolysis causes oxidative damage indirectly by generating reactive oxygen species through various pathophysiological mechanisms, which include hemoglobin autoxidation, endothelial nitric oxide synthase uncoupling, reduced nitric oxide bioavailability, and elevated levels of asymmetric dimethylarginine. Red blood cells have a built-in anti-oxidant system that includes enzymes like sodium dismutase, catalase, and glutathione peroxidase, along with free radical scavenging molecules, such as vitamin C, vitamin E, and glutathione, which help them to fight oxidative damage. However, these anti-oxidants may not be sufficient to prevent the effects of oxidative stress in SCD patients. Therefore, in line with a recent FDA request that the focus to be placed on the development of innovative therapies for SCD that address the root cause of the disease, there is a need for therapies that target oxidative stress and restore redox balance in SCD patients. This review summarizes the current state of knowledge regarding the role of oxidative stress in SCD and the potential benefits of anti-oxidant therapies. It also discusses the challenges and limitations of these therapies and suggests future directions for research and development.

Cardiovascular Consequences of Sickle Cell Disease

Background

Sickle cell disease is an inherited blood disorder which can lead to severe complications, particularly in the cardiovascular and respiratory systems, potentially resulting in arrhythmias, pulmonary hypertension (PH), and cardiomegaly. This study aims to investigate the risk of PH and arrhythmias in adult SCD patients.

Methods

Retrospective analysis of medical records from King Abdulaziz University Hospital (KAUH) for patients with SCD aged 15 and above between 2009 and 2021. The study included 517 patients, with echocardiograms and electrocardiograms assessed according to the European Society of Cardiology/the European Respiratory Society (ESC/ERS) guidelines for categorizing PH risk (low, moderate, high) and detecting arrhythmias. Data analysis employed the Statistical Package for the Social Sciences (SPSS), utilizing quantitative and qualitative data representation. Multivariate logistic regression identified independent risk factors with odds ratios at a 95% confidence interval (CI).

Results

Among participants, 50.3% were male, with a total sample average age of 34.45 ± 9.28 years. Results indicated that 1.4% of patients experienced arrhythmias, 3.7% had a moderate PH risk, and 3.3% were classified as high PH risk. Logistic regression revealed significant independent risk factors for PH and arrhythmia in patients with SCD, with chronic kidney disease (CKD) carrying the highest odds (26.4 times higher odds of PH and 15.36 times higher odds of arrhythmias).

Conclusion

Patients with SCD are at risk for developing PH and various arrhythmias but are often underdiagnosed. Key risk factors for PH included CKD, liver cirrhosis, and pre-existing cardiac conditions. Arrhythmias were significantly associated with CKD and pre-existing cardiac conditions. To mitigate these risks, we recommend involving a multidisciplinary healthcare team in the care of adult patients with SCD. Future prospective studies are advised for early detection of PH and arrhythmias in hemoglobinopathy patients, potentially reducing mortality.

Electrocardiographic abnormalities in patients with sickle cell disease: A systematic review and meta-analysis

BACKGROUND

Previous studies have documented that electrocardiography (ECG) can reveal a range of abnormalities, offering valuable insights into the cardiac evaluation of patients with sickle cell disease (SCD). The objective of this study is to assess the patterns of ECG abnormalities observed in these patients with SCD, and to determine their prevalence.

METHOD

We systematically reviewed the literature using online databases of PubMed, Scopus, Web of Science, Embase, and Google Scholar to identify original studies that reported findings of standard ECG assessments in patients with SCD. Statistical analyses were performed using the random effects model. Additional analyses including sensitivity analysis and subgroup analysis were also conducted.

RESULTS

Analysis of data from 59 studies involving 897,920 individuals with SCD revealed that 75% of these patients had abnormal ECG findings (67%-81%), which were predominantly nonspecific ST-T changes, left ventricular hypertrophy, T-wave changes, prolonged corrected QT (QTc) interval, and ischemic changes. Besides, it was shown that these patients had significantly higher odds of having any ECG abnormalities (OR of 17.50, 4.68-65.49), right atrial enlargement (6.09, 1.48-25.09), left ventricular hypertrophy (3.45, 1.73-6.89), right ventricular hypertrophy (7.18, 2.28-22.57), biventricular hypertrophy (10.11, 1.99-51.38), prolonged QTc interval (5.54, 2.44-12.59), ST depression (3.34, 1.87-5.97), and T-wave changes (5.41, 1.43-20.56). Moreover, the mean of QTc interval was significantly higher among those with SCD (23.51 milliseconds, 16.08-30.94).

CONCLUSION

Our meta-analysis showed a higher prevalence of abnormal ECG findings among individuals with SCD. A significant proportion of these patients had various ECG abnormalities, suggesting a potential need for regular ECG assessments for patients with SCD.

Acute care utilization among individuals with sickle cell disease and related cardiopulmonary and renal complications

Cardiopulmonary and renal end organ (CPR) complications are associated with early mortality among individuals with sickle cell disease (SCD). However, there is limited knowledge regarding acute care utilization for individuals with SCD and CPR complications. Our objective was to determine the prevalence of CPR complications in a state specific SCD population and compare acute care utilization among individuals with and without CPR complications. We leveraged 2017-2020 data for individuals with SCD identified by the Sickle Cell Data Collection program in Wisconsin. The prevalence of CPR complications is determined for distinct age groups. Generalized linear models adjusted for age compared the rate of acute care visits/person/year among individuals who had cardiopulmonary only, renal only, both cardiopulmonary and renal, or no CPR complications. There were 1378 individuals with SCD, 52% females, mean (SD) age 28.3 (18.5) years; 48% had at least one CPR complication during the study period. The prevalence of CPR complications was higher in adults (69%) compared to pediatric (15%) and transition (51%) groups. Individuals with SCD and cardiopulmonary complications had higher acute visit rates than those without CPR complications (5.4 (IQR 5.0-5.8) vs 2.4 (IQR 2.1-2.5), p <0.001)). Acute care visit rates were similar between individuals with SCD who had renal only complications and no CPR complications (2.7 (IQR 2.5-3.0) vs 2.4 (2.1-2.5), p = 0.24). The high acute care visit rates, especially for those with cardiopulmonary complications, warrant further investigation to understand risk factors for CPR complications, the underlying reasons and identify effective disease management strategies.

Pharmacogenomics of Drugs Used in β-Thalassemia and Sickle-Cell Disease: From Basic Research to Clinical Applications

In this short review we have presented and discussed studies on pharmacogenomics (also termed pharmacogenetics) of the drugs employed in the treatment of β-thalassemia or Sickle-cell disease (SCD). This field of investigation is relevant, since it is expected to help clinicians select the appropriate drug and the correct dosage for each patient. We first discussed the search for DNA polymorphisms associated with a high expression of γ-globin genes and identified this using GWAS studies and CRISPR-based gene editing approaches. We then presented validated DNA polymorphisms associated with a high HbF production (including, but not limited to the HBG2 XmnI polymorphism and those related to the BCL11A, MYB, KLF-1, and LYAR genes). The expression of microRNAs involved in the regulation of γ-globin genes was also presented in the context of pharmacomiRNomics. Then, the pharmacogenomics of validated fetal hemoglobin inducers (hydroxyurea, butyrate and butyrate analogues, thalidomide, and sirolimus), of iron chelators, and of analgesics in the pain management of SCD patients were considered. Finally, we discuss current clinical trials, as well as international research networks focusing on clinical issues related to pharmacogenomics in hematological diseases.

Homozygous Sickle Cell Disease after Age of 40: Follow-Up of a Cohort of 209 Patients in Senegal, West Africa

Objectives

The aim of this study was to describe the morbidity and mortality of homozygous sickle cell disease after the age of 40.

Methods

This was a cohort study of 209 patients followed from 1994 to 2022. All hemoglobin electrophoresis-confirmed SS sickle cell patients over 40 years were included. A descriptive study of epidemiological, diagnostic, therapeutic, and evolutionary data was used to assess morbidity and mortality.

Results

Sex ratio (M/F) was 0.6. Median age was 47 (41-75). According to morbidity, 95.1% had less than 3 vaso-occlusive crises/year. Acute anemia was the most frequent complication (52.63%). Chronic complications were noted in 32.5%. At diagnosis, mean hemoglobin was 8.1 g/dl ± 1.9, HbS was 86.5 ± 10, and HbF was 9.4 ± 7.6. Number of patients transfused was 66%. We noted that 8.1% of patients died, 29.2% were lost to follow-up, and 62.7% were still being followed up. The risk factors identified for death were geographical origin, comorbidity, high HbS, low HbF, and thrombocytosis.

Conclusion

This study shows that homozygous SCD is increasingly becoming an adult disease and that it can be carried into old age in Africa. Advanced age over 40 is marked by an upsurge in chronic complications, making it essential to set up a screening program and to organize multidisciplinary follow-up.

Enhancing diagnostic precision for acute chest syndrome in sickle cell disease: insights from dual-energy CT lung perfusion mapping

PURPOSE

Acute chest syndrome (ACS) is secondary to occlusion of the pulmonary vasculature and a potentially life-threatening complication of sickle cell disease (SCD). Dual-energy CT (DECT) iodine perfusion map reconstructions can provide a method to visualize and quantify the extent of pulmonary microthrombi.

METHODS

A total of 102 patients with sickle cell disease who underwent DECT CTPA with perfusion were retrospectively identified. The presence or absence of airspace opacities, segmental perfusion defects, and acute or chronic pulmonary emboli was noted. The number of segmental perfusion defects between patients with and without acute chest syndrome was compared. Sub-analyses were performed to investigate robustness.

RESULTS

Of the 102 patients, 68 were clinically determined to not have ACS and 34 were determined to have ACS by clinical criteria. Of the patients with ACS, 82.4% were found to have perfusion defects with a median of 2 perfusion defects per patient. The presence of any or new perfusion defects was significantly associated with the diagnosis of ACS (P = 0.005 and < 0.001, respectively). Excluding patients with pulmonary embolism, 79% of patients with ACS had old or new perfusion defects, and the specificity for new perfusion defects was 87%, higher than consolidation/ground glass opacities (80%).

CONCLUSION

DECT iodine map has the capability to depict microthrombi as perfusion defects. The presence of segmental perfusion defects on dual-energy CT maps was found to be associated with ACS with potential for improved specificity and reclassification.

Trends in prevalence of major etiologies leading to heart failure in young patients: An integrative review

The prevalence of Heart failure (HF) is increasing with the aging of the population but it is estimated that 10% of HF patients are younger than 50 years-old. HF development in this population is characterized with a fast-growing prevalence, and important disparities according to underlying etiologies or gender. These observations highlight the need to identify specific and preventable factors in these patients, a topic that is under-studied. Here we provide an overview of trends in prevalence of major etiologies leading to HF in young subjects, including genetic factors associated with cardiomyopathies, premature vascular dysfunction and related ischemia, metabolic stress, cardio-toxic responses to different agents, and myocarditis. We also highlight the increasing influence of major risk factors that are driving HF in younger patients, such as obesity, diabetes or arterial hypertension.

Genetic variants and effect modifiers of QT interval prolongation in patients with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is a common inherited blood disorder among African Americans (AA), with premature mortality which has been associated with prolongation of the heart rate-corrected QT interval (QTc), a known risk factor for sudden cardiac death. Although numerous genetic variants have been identified as contributors to QT interval prolongation in the general population, their impact on SCD patients remains unclear. This study used an unweighted polygenic risk score (PRS) to validate the previously identified associations between SNPs and QTc interval in SCD patients, and to explore possible interactions with other factors that prolong QTc interval in AA individuals with SCD.

METHODS

In SCD patients, candidate genetic variants associated with the QTc interval were genotyped. To identify any risk SNPs that may be correlated with QTc interval prolongation, linear regression was employed, and an unweighted PRS was subsequently constructed. The effect of PRS on the QTc interval was evaluated using linear regression, while stratification analysis was used to assess the influence of serum alanine transaminase (ALT), a biomarker for liver disease, on the PRS effect. We also evaluated the PRS with the two subcomponents of QTc, the QRS and JTc intervals.

RESULTS

Out of 26 candidate SNPs, five risk SNPs were identified for QTc duration under the recessive model. For every unit increase in PRS, the QTc interval prolonged by 4.0 ms (95% CI: [2.0, 6.1]; p-value: <0.001) in the additive model and 9.4 ms in the recessive model (95% CI: [4.6, 14.1]; p-value: <0.001). Serum ALT showed a modification effect on PRS-QTc prolongation under the recessive model. In the normal ALT group, each PRS unit increased QTc interval by 11.7 ms (95% CI: [6.3, 17.1]; p-value: 2.60E-5), whereas this effect was not observed in the elevated ALT group (0.9 ms; 95% CI: [-7.0, 8.8]; p-value: 0.823).

CONCLUSION

Several candidate genetic variants are associated with QTc interval prolongation in SCD patients, and serum ALT acts as a modifying factor. The association of a CPS1 gene variant in both QTc and JTc duration adds to NOS1AP as evidence of involvement of the urea cycle and nitric oxide metabolism in cardiac repolarization in SCD. Larger replication studies are needed to confirm these findings and elucidate the underlying mechanisms.

Mouse models of sickle cell disease: Imperfect and yet very informative

The root cause of sickle cell disease (SCD) has been known for nearly a century, however, few therapies to treat the disease are available. Over several decades of work, with advances in gene editing technology and after several iterations of mice with differing genotype/phenotype relationships, researchers have developed humanized SCD mouse models. However, while a large body of preclinical studies has led to huge gains in basic science knowledge about SCD in mice, this knowledge has not led to the development of effective therapies to treat SCD-related complications in humans, thus leading to frustration with the paucity of translational progress in the SCD field. The use of mouse models to study human diseases is based on the genetic and phenotypic similarities between mouse and humans (face validity). The Berkeley and Townes SCD mice express only human globin chains and no mouse hemoglobin. With this genetic composition, these models present many phenotypic similarities, but also significant discrepancies that should be considered when interpreting preclinical studies results. Reviewing genetic and phenotypic similarities and discrepancies and examining studies that have translated to humans and those that have not, offer a better perspective of construct, face, and predictive validities of humanized SCD mouse models.

Cardiovascular complications of sickle cell disease: A primer for the general clinician

Sickle cell disease (SCD) is the most common hereditary hemoglobinopathy and mainly affects individuals of African ancestry. As survival has improved especially in high-income countries, increased rates of cardiopulmonary complications such as pulmonary hypertension, heart failure with diastolic dysfunction, and sudden death are encountered in clinical practice. These complications are the leading causes of morbidity and mortality as these individuals survive into adulthood. Understanding the need for, early identification, timely intervention, and implementation of preventive strategies are critical in reversing this trend and improving quality of life and survival rates. This manuscript aims to provide a comprehensive review of the pathogenesis of cardiovascular complications associated with sickle cell disease and equip the clinician with tools to facilitate the early diagnosis and management of patients with SCD as increasing numbers survive into adulthood.

Clinical and Laboratory Correlates of QTc Duration in Adult and Pediatric Sickle Cell Disease

Background

Sickle cell disease, a common genetic disorder in African Americans, manifests an increased risk of sudden death, the basis of which is incompletely understood. Prolongation of heart rate-corrected QT (QTc) interval on the electrocardiogram, a standard clinical measure of cardiac repolarization, may contribute to sudden death by predisposing to torsades de pointes ventricular tachycardia.

Methods

We established a cohort study of 293 adult and 121 pediatric sickle cell disease patients drawn from the same geographic region as the Jackson Heart Study (JHS) cohort, in which significant correlates of QT duration have been characterized and quantitatively modeled. Herein, we establish clinical and laboratory correlates of QTc duration in our cohort using stepwise multivariate linear regression analysis. We then compared our adult sickle cell disease data to effect-size predictions from the published JHS statistical model of QT interval duration.

Results

In adult sickle cell disease, gender, diuretic use, QRS duration, serum ALT levels, anion gap, and diastolic blood pressure show positive correlation; hemoglobin levels show inverse correlation; in pediatric sickle cell disease, age, hemoglobin levels, and serum bicarbonate and creatinine levels show inverse correlation. The mean QTc in our adult sickle cell disease cohort is 7.8 milliseconds longer than in the JHS cohort, even though the JHS statistical model predicts that the mean QTc in our cohort should be > 11 milliseconds shorter than in the much older JHS cohort, a differential of > 18 milliseconds.

Conclusion

Sickle cell disease patients have substantial QTc prolongation relative to their age, driven by factors some overlapping, in adult and pediatric sickle cell disease, and distinct from those that have been defined in the general African American community.

Evaluation of cardiac fibrosis and subclinical cardiac changes in children with sickle cell disease using magnetic resonance imaging, echocardiography, and serum galectin-3

BACKGROUND

Myocardial fibrosis has recently been proposed as one of the contributing factors to the diverse pathogenicity of cardiomyopathy in sickle cell disease.

OBJECTIVE

In this study, cardiac fibrosis and subclinical cardiac changes in children with sickle cell disease were evaluated using cardiac magnetic resonance imaging (MRI), tissue Doppler echocardiography and serum galectin-3.

MATERIALS AND METHODS

The study included 34 children with sickle cell disease who were compared with a similar number of healthy controls. Cardiac MRI was used to evaluate late gadolinium enhancement, native T1 mapping, extracellular volume, and T2* for estimation of iron load. Cardiac function and myocardial performance index (MPI, evaluated by tissue Doppler echocardiography) and serum galectin-3 were compared to controls.

RESULTS

The mean age of the included patients was 13.3 ± 3.2 years. Myocardial iron load by T2* was normal. The mean level of extracellular volume (35.41 ± 5.02%) was significantly associated with the frequency of vaso-occlusive crises (P = 0.017) and negatively correlated with hemoglobin levels (P = 0.005). Galectin-3 levels were significantly higher among cases than controls (P = 0.00), at a cutoff value on the receiver operating characteristic curve of 6.5 ng/ml, sensitivity of 82.5% and specificity of 72.8%. The extracellular volume was significantly higher in cases, with a MPI > 0.4.

CONCLUSION

Diffuse interstitial myocardial fibrosis can be detected early in children with sickle cell disease using T1 mapping and is associated with a high frequency of vaso-occlusive crisis. MPI of the left ventricle and serum galectin-3 are recommended screening tools for subclinical cardiac abnormalities.

The association of sickle cell disorder with adverse outcomes in COVID-19 patients: A meta-analysis

The aim is to elucidate the relationship between sickle cell disorder and severe COVID-19. We systematically searched the required articles in three electronic databases, extracting and pooling effect sizes (ES) and 95% confidence interval (CI) from each eligible study to evaluate the effect of combined sickle cell disorder on adverse consequences in patients with COVID-19. This meta-analysis included 21 studies. Sickle cell disease (SCD) was a risk factor for mortality (pooled ES = 1.70, 95% CI: 1.00-2.92, p = 0.001), hospitalization (pooled ES = 6.21, 95% CI: 3.60-10.70, p = 0.000) and intensive care unit (ICU) admission (pooled ES = 2.29, 95% CI: 1.61-3.24, p = 0.099) in COVID-19 patients. Patients with SCD had an increased risk of respiratory failure/mechanical ventilation, but a statistical association was not found (pooled ES = 1.21, 95%CI: 0.74-1.98, p = 0.036). There was significant heterogeneity between SCD and death, hospitalization, and respiratory failure/mechanical ventilation. The results of meta-regression of SCD and hospitalization suggested that the tested variables including Area (p = 0.642), study design (p = 0.739), sample size (p = 0.397), proportion of males (p = 0.708), effect type (p = 0.723), whether confounding factors are adjusted (p = 0.606) might not be the source of heterogeneity. In addition, sickle cell trait (SCT) was significantly associated with the mortality (pooled ES = 1.54, 95% CI: 1.28-1.85, p = 0.771) and hospitalization (pooled ES = 1.20, 95% CI: 1.07-1.35，p = 0.519) in patients with COVID-19. But any increased risk of ICU admission/severe (pooled ES = 1.24, 95% CI: 0.95-1.62, p = 0.520) and mechanical ventilation (OR = 1.00, 95%CI:0.59-1.69) in COVID-19 patients with SCT was not observed. Sensitivity analysis demonstrated that the results were robust. The results of the funnel plot and Egger's test did not support the existence of publication bias. Current meta-analysis indicated that sickle cell disorder has a meaningful impact on COVID-19 progression to severe cases and associated deaths. However, further investigations and research to validate the current findings is indispensable.

Cervical precancer screening with HPV DNA testing and mobile colposcopy in women with sickle cell disease in Accra, Ghana

Background

Worldwide, about 20-25 million people are affected by sickle cell disease (SCD), with 60% of patients living in sub-Saharan Africa. Despite recent therapeutic advancements resulting in improved life expectancy among SCD patients, the prevalence of high-risk human papillomavirus (hr-HPV) and cervical lesions have not been studied in women with SCD. We determined the prevalence of hr-HPV and cervical lesions among women with SCD and recommended strategies for reducing cervical cancer incidence in this cohort.

Methods

Through the mPharma 10,000 Women Initiative, women with SCD attending routine visits at the Ghana Institute of Clinical Genetics SCD clinic were screened by trained nurses. Screening was performed via concurrent MA-6000 hr-HPV DNA testing and enhanced visual assessment (EVA) mobile colposcopy from mobileODT.

Results

Among 168 participants screened (mean age, 43.0 years), the overall prevalence rates of hr-HPV infection and cervical lesions were 28.6% (95% CI, 21.7-35.4) and 3.6% (95% CI, 0.8-6.4), respectively. The hr-HPV prevalence rates stratified by haemoglobin genotype were 29.4% (95% CI, 19.7-39.1) and 28.6% (95% CI, 18.5-38.7) for genotypes SS and SC, respectively. None of the five women with the SF genotype tested hr-HPV positive, and the only patient with Sbthal genotype tested hr-HPV positive. Two women were EVA 'positive' but hr-HPV negative, whereas four were EVA positive and hr-HPV positive. Exploratory analysis revealed no significant associations between hr-HPV positivity and age, education level, marital status or parity.

Conclusion

In the absence of a comprehensive national cervical screening programme aimed at including women with SCD as a special population, cervical cancer may increase in frequency among SCD patients. Thus, there is a need to build capacity and expand the scope of screening services for women with SCD.

RASA3 is a candidate gene in sickle cell disease-associated pulmonary hypertension and pulmonary arterial hypertension

Pulmonary hypertension (PH) is associated with significant morbidity and mortality. RASA3 is a GTPase activating protein integral to angiogenesis and endothelial barrier function. In this study, we explore the association of RASA3 genetic variation with PH risk in patients with sickle cell disease (SCD)-associated PH and pulmonary arterial hypertension (PAH). Cis-expression quantitative trait loci (eQTL) were queried for RASA3 using whole genome genotype arrays and gene expression profiles derived from peripheral blood mononuclear cells (PBMC) of three SCD cohorts. Genome-wide single nucleotide polymorphisms (SNPs) near or in the RASA3 gene that may associate with lung RASA3 expression were identified, reduced to 9 tagging SNPs for RASA3 and associated with markers of PH. Associations between the top RASA3 SNP and PAH severity were corroborated using data from the PAH Biobank and analyzed based on European or African ancestry (EA, AA). We found that PBMC RASA3 expression was lower in patients with SCD-associated PH as defined by echocardiography and right heart catheterization and was associated with higher mortality. One eQTL for RASA3 (rs9525228) was identified, with the risk allele correlating with PH risk, higher tricuspid regurgitant jet velocity and higher pulmonary vascular resistance in patients with SCD-associated PH. rs9525228 associated with markers of precapillary PH and decreased survival in individuals of EA but not AA. In conclusion, RASA3 is a novel candidate gene in SCD-associated PH and PAH, with RASA3 expression appearing to be protective. Further studies are ongoing to delineate the role of RASA3 in PH.

Diaphragm excursion correlates with performance and ventilation on the 6-min walk test in children with sickle cell disease

INTRODUCTION

Diaphragm function may be impaired in children with sickle cell disease (SCD). We hypothesized that diaphragm function is related to performance and ventilation on the 6-min walk test (6MWT).

METHODS

Respiratory muscle testing, diaphragm ultrasonography, and the 6MWT with portable gas analysis were performed on children with SCD and age- and sex-matched controls.

RESULTS

Fourteen children with SCD were enrolled. Comparisons were made between nine children with SCD (9.89  ± $\pm $  2.93 years) and nine controls (10.33  ± $\pm $  2.35 years). Diaphragm thickness at total lung capacity, thickening fraction, and excursion time during quiet breaths and deep breaths (DB), all normalized by forced vital capacity, were greater in children with SCD ( p < $p\lt $ 0.05 for all). 6MWT distance was shorter in children with SCD (450.87  ± $\pm $  74.2 m vs. 579.22 ± $\pm $ 72.46 m, p = $p=$ 0.01). Tidal volume ( V T ${V}_{T}$ ), minute ventilation ( V ˙ E ${\dot{V}}_{E}$ ), and oxygen consumption ( V ˙ O 2 ${\dot{V}}_{{O}_{2}}$ ) were also lower ( p < $p\lt $ 0.05 for all). DB excursion correlated positively with 6MWT distance ( r = $r=$ 0.648, p = $p=$ 0.023) and negatively with rate of perceived exertion (RPE) ( r = $r=$ -0.759, p = $p=$ 0.003). RPE correlated negatively with distance ( r = $r=$ -0.680, p = $p=$ 0.015). DB excursion time correlated positively with distance ( r = $r=$ 0.611, p = $p=$ 0.035), V T ${V}_{T}$ ( r = $r=$ 0.770, p = $p=$ 0.009), V ˙ E ${\dot{V}}_{E}$ ( r = $r=$ 0.736, p = $p=$ 0.015), and V ˙ O 2 ${\dot{V}}_{{O}_{2}}$ ( r = $r=$ 0.751, p = $p=$ 0.012).

CONCLUSIONS

Increased diaphragm excursion may be a strategy used to relieve air hunger while longer excursion time may reflect compensations to increase lung recruitment. Further studies are needed to better understand how these mechanisms affect exercise tolerance in children with SCD.

The Role of Inflammation in The Cellular and Molecular Mechanisms of Cardiopulmonary Complications of Sickle Cell Disease

Cardiopulmonary complications remain the major cause of mortality despite newer therapies and improvements in the lifespan of patients with sickle cell disease (SCD). Inflammation has been identified as a major risk modifier in the pathogenesis of SCD-associated cardiopulmonary complications in recent mechanistic and observational studies. In this review, we discuss recent cellular and molecular mechanisms of cardiopulmonary complications in SCD and summarize the most recent evidence from clinical and laboratory studies. We emphasize the role of inflammation in the onset and progression of these complications to better understand the underlying pathobiological processes. We also discuss future basic and translational research in addressing questions about the complex role of inflammation in the development of SCD cardiopulmonary complications, which may lead to promising therapies and reduce morbidity and mortality in this vulnerable population.

Prognostic value of multiparametric cardiac magnetic resonance in sickle cell patients

The aim of this multicenter study was to prospectively assess the predictive value of multiparametric cardiac magnetic resonance (CMR) for cardiovascular complications in sickle cell disease (SCD) patients. Among all patients with hemoglobinopathies consecutively enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) Network, we selected 102 SCD patients (34.38 ± 12.67 years, 49 females). Myocardial iron overload (MIO) was measured by the multislice multiecho T2* technique. Atrial dimensions and biventricular function parameters were quantified by cine images. Late gadolinium enhancement (LGE) images were acquired to detect focal myocardial fibrosis. At baseline CMR, only two patients had significant MIO (global heart T2* < 20 ms). During a mean follow-up of 63.01 ± 24.95 months, 11 cardiovascular events (10.8%) were registered: 3 pulmonary hypertension, 2 supraventricular arrhythmias, 1 heart failure, 1 death for heart failure, 1 pulmonary embolism, 1 peripheral vascular disease, 1 transient ischemic attack, and 1 death after acute chest syndrome. In the multivariate analysis, the independent CMR predictors of cardiovascular events were left ventricular (LV) ejection fraction (hazard ratio-HR = 0.88; p = 0.025) and right ventricular (RV) mass index (HR = 1.09; p = 0.047). According to the receiver-operating characteristic curve analysis for adverse events, an LV ejection fraction < 58.9% and an RV mass index > 31 g/m² were optimal cut-off values. Reduced left ventricular ejection fraction and increased right ventricular mass index showed a significant prognostic value in patients with SCD. Our data seem to suggest that CMR may be added as a screening tool for identifying SCD patients at high risk for cardiopulmonary and vascular diseases.

Associations of hemolysis and anemia with cardiopulmonary dysfunction in an adult sickle cell disease cohort

BACKGROUND

Hemolysis contributes to the anemia of sickle cell disease (SCD). Hemolysis and anemia are distinct but inter-related pathophysiological processes that underlie end-organ dysfunction in this condition. We hypothesized that real-world medical tests would reveal distinct contributions of hemolysis and anemia to certain cardiopulmonary changes in adults with SCD.

METHODS

We assessed laboratory and clinical tests of cardiopulmonary function obtained during routine delivery of care in 442 adult SCD patients. We characterized hemolysis by the first principal component (PC1) of reticulocyte percent, lactate dehydrogenase (LDH), aspartate amino transferase (AST) and total bilirubin- the hemolytic component. The relationships of hemoglobin concentration and hemolysis to organ dysfunction were analyzed by multiple regression and path analysis to identify independent associations.

RESULTS

Degree of hemolysis and degree of anemia both associated independently with elevated values for left atrial diameter (LAD) and left ventricular end-diastolic diameter (LVED), and with lower percent predicted forced expiratory volume in first second (FEV1). Degree of hemolysis, but not anemia, associated independently with low values for oxygen saturation, forced vital capacity (FVC), and total lung capacity (TLC)]. Path analysis reinforced the trend by multiple regression for association of both degree of hemolysis and anemia with elevated TRV but not with lower diastolic blood pressure.

DISCUSSION

Analysis of real-world clinical tests suggest that, although they are inter-related, the degrees of hemolysis and of anemia make independent contributions to cardiopulmonary dysfunction and that treatments that specifically target both aspects of sickle cell disease may be of maximal benefit.

Pediatric Sickle Cell Disease in Sudan: Complications and Management

Background. Sickle cell disease (SCD) is a life-threatening genetic disorder due to the formation of sickle hemoglobin molecule (HbS) that polymerizes in hypoxic conditions leading to SCD-related complications. Different approaches have been used in the management of SCD including symptomatic management, supportive management, and preventive management. Objectives. To assess the management of SCD in pediatric patients in Gaafar Ibnauf Referral Hospital in Khartoum locality, Sudan. Method. A descriptive, retrospective, hospital-based study was conducted in Gaafar Ibnauf Hospital using a data collection sheet. The study included all medical files of pediatric patients with SCD attending the hospital during the period from the first of April 2018 to the first of July 2018. The data were analyzed using descriptive statistics and the chi-square test. $P<0.05$ was considered statistically significant. Results. Out of 207 pediatric patients, 53.1% were females (mean age of 7.5 ± 3.1 years), with a 1.1 : 1 female:male ratio and low socioeconomic status. Only 4.3% of participants had health insurance. The Messeryia tribe in western Sudan had the highest prevalence of the disease among the Sudanese tribes (11.1%). Vaso-occlusive crisis (33.3%), infections (13.5%), and neurological complications (10.6%) were the most frequent complications reported during routine visits. After initiation of management, only 3.4% of pediatric patients had hemolytic crises, and 1.4% of the anemic patients had splenomegaly. 100% of patients received folic acid, 73.9% used hydroxyurea, and 69.6% underwent blood transfusion for the management of SCD. Prophylactic penicillin was prescribed for 15% of patients, and 41.1% were immunized with pneumococcal vaccine (PPSV23). Most patients had been scheduled for planned follow-up visits every 3–6 months (93.2%). Hydroxyurea and blood transfusion significantly reduced fever and vaso-occlusive crisis. Conclusion. The SCD treatment protocol in Gaafar Ibnauf Children’s Hospital, involving preventive and symptomatic therapy, is consistent with the internationally implemented protocols for SCD management. However, immunization and prophylactic penicillin approaches are deficient.

Exercise-induced changes of vital signs in adults with sickle cell disease

The six-minute walk test (6MWT) has been used in patients with sickle cell disease (SCD), in conjunction with tricuspid regurgitant velocity (TRV) and plasma N-terminal pro-brain natriuretic peptide (NT-pro BNP), to assess risk of having pulmonary hypertension. Exercise-induced vital sign changes (VSCs) are predictors of clinical outcomes in other diseases. In this study, we assess the predictors and prognostic value of 6MWT VSC in adult SCD patients. Data from a multinational study of SCD patients (Treatment of Pulmonary Hypertension with Sildenafil: walk-PHaSST) were used to calculate the 6MWT VSC. Predictors of VSC were identified by a multivariable analysis, and a survival analysis was conducted by the Cox proportional hazard method. An increase in heart rate was observed in 90% of the 630 SCD adults, 77% of patients had an increase in systolic blood pressure (SBP), and 50% of patients had a decrease in oxygen saturation. TRV (odds ratio [OR] = 1.82, p = .020), absolute reticulocyte count (OR = 1.03, p < .001), and hemoglobin (OR = 0.99, p = .035) predicted oxygen desaturation ≥ 3% during the 6MWT. In the adjusted analysis, SBP increase during the 6MWT was associated with improved survival (hazards ratio = 0.3, 95% confidence interval: 0.1-0.8). Increases in heart rate and blood pressure, as well as oxygen desaturation, are common in adults with SCD during the 6MWT. VSC is associated with markers of anemia and TRV and can be used for risk stratification. Any increase in SBP during the 6MWT was associated with improved survival and may be indicative of a patient's ability to increase stroke volume.

Assessment of cystatin C in pediatric sickle cell disease and β-thalassemia as a marker of subclinical cardiovascular dysfunction: a case-control study

Cardiovascular complications represent the main determinant of survival in patients with hemoglobinopathies. Serum cystatin C is a well-known marker of nephropathy in sickle cell disease (SCD) and β-thalassemia patients that has recently emerged as a strong predictor of cardiovascular dysfunction in patients with and without kidney disease. We performed a case control study to determine the role of cystatin C as a predictor of subclinical cardiovascular dysfunction in SCD and β-thalassemia patients. We enrolled 40 SCD patients with a mean age of 12.4 years, 40 β-thalassemia patients with a mean age of 11.4 years and 40 age and sex-matched controls. We assessed hematological profile, serum ferritin, urinary albumin-creatinine ratio (UACR), serum cystatin C, echocardiography and carotid intima media thickness (CIMT). UACR, cystatin C and CIMT were higher in SCD and β-thalassemia patients compared to controls (p < .001). Significantly higher cystatin C levels were observed in SCD and β-thalassemia patients with nephropathy or left ventricular systolic dysfunction (shortening fraction <30%, or ejection fraction <55%; p < .001). Moreover, SCD patients with pulmonary hypertension had significantly higher cystatin C levels. Cystatin C levels were positively correlated with CIMT in SCD (p = .02) and β-thalassemia patients (p < .001) while negatively correlated with ejection fraction and shortening fraction (p < .001). The cutoff values of cystatin C ≥ 16.03 and ≥ 13.2 (ng/mL) could detect subclinical cardiac dysfunction risk among SCD and β-thalassemia patients respectively. Cystatin C appears to be a promising marker for subclinical cardiovascular dysfunction in SCD and β-thalassemia patients.

The different facets of sickle cell disease-related pulmonary hypertension

PURPOSE OF REVIEW

Sickle cell disease (SCD), one of the most common genetic diseases in the world, is characterized by repeated episodes of hemolysis and vaso-occlusion. Hemolytic anemia is a risk factor for the development of pulmonary hypertension, and currently SCD-related pulmonary hypertension is classified as World Health Organization group 5 pulmonary hypertension. Patients with SCD-related pulmonary hypertension have unique hemodynamics, multiple comorbidities, and distinct phenotypes that may contribute to the development of pulmonary hypertension.

RECENT FINDINGS

SCD-related pulmonary hypertension is defined as a mean pulmonary artery pressure >20 mmHg, a pulmonary artery occlusion pressure ≤15 mmHg and relatively low pulmonary vascular resistance (>2 Wood units) rather than the traditional definition of ≥3 Wood units, an important distinction due to a baseline high-cardiac output state in the setting of chronic anemia and low vascular resistance. Diastolic dysfunction is frequently identified in this patient population and right heart catheterization is essential to determine if combined pre- and postcapillary pulmonary hypertension is present. Thromboembolism is common among patients with SCD, and screening for chronic thromboembolic pulmonary hypertension is essential. Data regarding advanced therapies are limited. Primary treatment options include targeting correction of their primary hemoglobinopathy as well as aggressive management of underlying comorbid conditions.

SUMMARY

SCD-related pulmonary hypertension is common among patients with SCD and is associated with increased mortality. A high index of suspicion is warranted during evaluation to identify all potential factors that may be contributing to disease.

Discrimination of single-point mutations in unamplified genomic DNA via Cas9 immobilized on a graphene field-effect transistor

Simple and fast methods for the detection of target genes with single-nucleotide specificity could open up genetic research and diagnostics beyond laboratory settings. We recently reported a biosensor for the electronic detection of unamplified target genes using liquid-gated graphene field-effect transistors employing an RNA-guided catalytically deactivated CRISPR-associated protein 9 (Cas9) anchored to a graphene monolayer. Here, using unamplified genomic samples from patients and by measuring multiple types of electrical response, we show that the biosensors can discriminate within one hour between wild-type and homozygous mutant alleles differing by a single nucleotide. We also show that biosensors using a guide RNA-Cas9 orthologue complex targeting genes within the protospacer-adjacent motif discriminated between homozygous and heterozygous DNA samples from patients with sickle cell disease, and that the biosensors can also be used to rapidly screen for guide RNA-Cas9 complexes that maximize gene-targeting efficiency.

A phenotypic risk score for predicting mortality in sickle cell disease

Risk assessment for patients with sickle cell disease (SCD) remains challenging as it depends on an individual physician's experience and ability to integrate a variety of test results. We aimed to provide a new risk score that combines clinical, laboratory, and imaging data. In a prospective cohort of 600 adult patients with SCD, we assessed the relationship of 70 baseline covariates to all-cause mortality. Random survival forest and regularised Cox regression machine learning (ML) methods were used to select top predictors. Multivariable models and a risk score were developed and internally validated. Over a median follow-up of 4·3 years, 131 deaths were recorded. Multivariable models were developed using nine independent predictors of mortality: tricuspid regurgitant velocity, estimated right atrial pressure, mitral E velocity, left ventricular septal thickness, body mass index, blood urea nitrogen, alkaline phosphatase, heart rate and age. Our prognostic risk score had superior performance with a bias-corrected C-statistic of 0·763. Our model stratified patients into four groups with significantly different 4-year mortality rates (3%, 11%, 35% and 75% respectively). Using readily available variables from patients with SCD, we applied ML techniques to develop and validate a mortality risk scoring method that reflects the summation of cardiopulmonary, renal and liver end-organ damage. Trial Registration: ClinicalTrials.gov Identifier: NCT#00011648.