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Liu A, Jacobs-McFarlane C, Sebastiani P, Glassberg J, McCuskee S, Curtis S. Plasma free hemoglobin is associated with LDH, AST, total bilirubin, reticulocyte count, and the hemolysis score in patients with sickle cell anemia. RESEARCH SQUARE 2024:rs.3.rs-4252554. [PMID: 38746469 PMCID: PMC11092852 DOI: 10.21203/rs.3.rs-4252554/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Plasma free hemoglobin (PFH) is a direct biomarker for hemolysis that has been associated with clinical complications such as pulmonary hypertension and death in patients with sickle cell disease (SCD). We sought to characterize the relationship between PFH and more clinically available hemolytic markers including lactate dehydrogenase (LDH), aspartate aminotransferase (AST), bilirubin, reticulocyte percentage and to derive a composite hemolysis score derived from principal component analysis (PCA) of these biomarkers. In 68 adult patients (median age 31 years old, IQR 25-39) with HbSS or HbSβ0-thalassemia enrolled in the IMPROVE II study, median PFH was elevated at 21.9 mg/dL (IQR 9.9-44.9 mg/dL). Using Pearson correlation analysis, PFH had a stronger relationship to LDH (R=0.699), AST (R=0.587), and total bilirubin (R=0.475), compared to reticulocyte count (R=0.316). The hemolysis score was significantly associated with PFH (R=0.677). When compared with other laboratory measures, PFH correlated with hemoglobin (R= -0.275) and HbS (R=0.277),but did not correlate with white blood cell count (WBC) or HbF. The hemolysis score was significantly associated with WBC (R=0.307), hemoglobin (R = -0.393), HbF (R=- 0.424), and HbS (R=0.423). This study confirms that the conventional hemolytic biomarkers LDH, AST, bilirubin, and reticulocyte percentage correlate with PFH. Additionally, the hemolysis score is a valid tool to measure hemolysis and that it may be a marker of global hemolysis as opposed to PFH, which quantifies intravascular hemolysis. Further studies will be needed to elucidate the role of PFH and intravascular hemolysis in the development of clinical complications of sickle cell disease.
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Kirkham JK, Estepp JH, Weiss MJ, Rashkin SR. Genetic Variation and Sickle Cell Disease Severity: A Systematic Review and Meta-Analysis. JAMA Netw Open 2023; 6:e2337484. [PMID: 37851445 PMCID: PMC10585422 DOI: 10.1001/jamanetworkopen.2023.37484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/30/2023] [Indexed: 10/19/2023] Open
Abstract
Importance Sickle cell disease (SCD) is a monogenic disorder, yet clinical outcomes are influenced by additional genetic factors. Despite decades of research, the genetics of SCD remain poorly understood. Objective To assess all reported genetic modifiers of SCD, evaluate the design of associated studies, and provide guidelines for future analyses according to modern genetic study recommendations. Data Sources PubMed, Web of Science, and Scopus were searched through May 16, 2023, identifying 5290 publications. Study Selection At least 2 reviewers identified 571 original, peer-reviewed English-language publications reporting genetic modifiers of human SCD phenotypes, wherein the outcome was not treatment response, and the comparison was not between SCD subtypes or including healthy controls. Data Extraction and Synthesis Data relevant to all genetic modifiers of SCD were extracted, evaluated, and presented following STREGA and PRISMA guidelines. Weighted z score meta-analyses and pathway analyses were conducted. Main Outcomes and Measures Outcomes were aggregated into 25 categories, grouped as acute complications, chronic conditions, hematologic parameters or biomarkers, and general or mixed measures of SCD severity. Results The 571 included studies reported on 29 670 unique individuals (50% ≤ 18 years of age) from 43 countries. Of the 17 757 extracted results (4890 significant) in 1552 genes, 3675 results met the study criteria for meta-analysis: reported phenotype and genotype, association size and direction, variability measure, sample size, and statistical test. Only 173 results for 62 associations could be cross-study combined. The remaining associations could not be aggregated because they were only reported once or methods (eg, study design, reporting practice) and genotype or phenotype definitions were insufficiently harmonized. Gene variants regulating fetal hemoglobin and α-thalassemia (important markers for SCD severity) were frequently identified: 19 single-nucleotide variants in BCL11A, HBS1L-MYB, and HBG2 were significantly associated with fetal hemoglobin (absolute value of Z = 4.00 to 20.66; P = 8.63 × 10-95 to 6.19 × 10-5), and α-thalassemia deletions were significantly associated with increased hemoglobin level and reduced risk of albuminuria, abnormal transcranial Doppler velocity, and stroke (absolute value of Z = 3.43 to 5.16; P = 2.42 × 10-7 to 6.00 × 10-4). However, other associations remain unconfirmed. Pathway analyses of significant genes highlighted the importance of cellular adhesion, inflammation, oxidative and toxic stress, and blood vessel regulation in SCD (23 of the top 25 Gene Ontology pathways involve these processes) and suggested future research areas. Conclusions and Relevance The findings of this comprehensive systematic review and meta-analysis of all published genetic modifiers of SCD indicated that implementation of standardized phenotypes, statistical methods, and reporting practices should accelerate discovery and validation of genetic modifiers and development of clinically actionable genetic profiles.
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Affiliation(s)
- Justin K. Kirkham
- Department of Oncology, St Jude Children’s Research Hospital, Memphis, Tennessee
| | - Jeremie H. Estepp
- Department of Hematology, St Jude Children’s Research Hospital, Memphis, Tennessee
- Department of Global Pediatric Medicine, St Jude Children’s Research Hospital, Memphis, Tennessee
- Now with Agios Pharmaceuticals, Cambridge, Massachusetts
| | - Mitch J. Weiss
- Department of Hematology, St Jude Children’s Research Hospital, Memphis, Tennessee
| | - Sara R. Rashkin
- Department of Hematology, St Jude Children’s Research Hospital, Memphis, Tennessee
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Esperti S, Boisson C, Robert M, Nader E, Cibiel A, Renoux C, Horrand F, Gauthier A, Poutrel S, Joly P, Connes P. Does G6PD deficiency cause further damage to red blood cells of patients with sickle cell anaemia? Br J Haematol 2022; 199:289-291. [PMID: 35973746 DOI: 10.1111/bjh.18417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 08/03/2022] [Accepted: 08/07/2022] [Indexed: 11/29/2022]
Affiliation(s)
- Sofia Esperti
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France.,Erytech Pharma, Lyon, France
| | - Camille Boisson
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France
| | - Mélanie Robert
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France.,Erytech Pharma, Lyon, France
| | - Elie Nader
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France
| | | | - Céline Renoux
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France.,Laboratoire de Biochimie et de Biologie Moléculaire, UF de Biochimie des Pathologies Erythrocytaires, Centre de Biologie et de Pathologie Est, Hospices Civils de Lyon, Bron, France
| | | | - Alexandra Gauthier
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France.,Institut d'Hématologique et d'Oncologique Pédiatrique, Hospices Civils de Lyon, Lyon, France
| | - Solène Poutrel
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France.,Service de Médecine Interne, Hôpital Edouard Herriot, Hospices Civils de Lyon, Lyon, France
| | - Philippe Joly
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France.,Laboratoire de Biochimie et de Biologie Moléculaire, UF de Biochimie des Pathologies Erythrocytaires, Centre de Biologie et de Pathologie Est, Hospices Civils de Lyon, Bron, France
| | - Philippe Connes
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team "Vascular Biology and Red Blood Cell" Universié Claude Bernard Lyon 1, Université de Lyon, Lyon, France.,Laboratoire d'Excellence du Globule Rouge (Labex GR-Ex), PRES Sorbonne, Paris, France
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Will the Use of Pharmacogenetics Improve Treatment Efficiency in COVID-19? Pharmaceuticals (Basel) 2022; 15:ph15060739. [PMID: 35745658 PMCID: PMC9230944 DOI: 10.3390/ph15060739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 12/13/2022] Open
Abstract
The COVID-19 pandemic is associated with a global health crisis and the greatest challenge for scientists and doctors. The virus causes severe acute respiratory syndrome with an outcome that is fatal in more vulnerable populations. Due to the need to find an efficient treatment in a short time, there were several drugs that were repurposed or repositioned for COVID-19. There are many types of available COVID-19 therapies, including antiviral agents (remdesivir, lopinavir/ritonavir, oseltamivir), antibiotics (azithromycin), antiparasitics (chloroquine, hydroxychloroquine, ivermectin), and corticosteroids (dexamethasone). A combination of antivirals with various mechanisms of action may be more efficient. However, the use of some of these medicines can be related to the occurrence of adverse effects. Some promising drug candidates have been found to be ineffective in clinical trials. The knowledge of pharmacogenetic issues, which translate into variability in drug conversion from prodrug into drug, metabolism as well as transport, could help to predict treatment efficiency and the occurrence of adverse effects in patients. However, many drugs used for the treatment of COVID-19 have not undergone pharmacogenetic studies, perhaps as a result of the lack of time.
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Pharmacogenomics and COVID-19: clinical implications of human genome interactions with repurposed drugs. THE PHARMACOGENOMICS JOURNAL 2021; 21:275-284. [PMID: 33542445 PMCID: PMC7859465 DOI: 10.1038/s41397-021-00209-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 12/07/2020] [Accepted: 01/15/2021] [Indexed: 02/07/2023]
Abstract
The outbreak of Coronavirus disease 2019 (COVID-19) has evolved into an emergent global pandemic. Many drugs without established efficacy are being used to treat COVID-19 patients either as an offlabel/compassionate use or as a clinical trial. Although drug repurposing is an attractive approach with reduced time and cost, there is a need to make predictions on success before the start of therapy. For the optimum use of these repurposed drugs, many factors should be considered such as drug–gene or dug–drug interactions, drug toxicity, and patient co-morbidity. There is limited data on the pharmacogenomics of these agents and this may constitute an obstacle for successful COVID-19 therapy. This article reviewed the available human genome interactions with some promising repurposed drugs for COVID-19 management. These drugs include chloroquine (CQ), hydroxychloroquine (HCQ), azithromycin, lopinavir/ritonavir (LPV/r), atazanavir (ATV), favipiravir (FVP), nevirapine (NVP), efavirenz (EFV), oseltamivir, remdesivir, anakinra, tocilizumab (TCZ), eculizumab, heme oxygenase 1 (HO-1) regulators, renin–angiotensin–aldosterone system (RAAS) inhibitors, ivermectin, and nitazoxanide. Drug-gene variant pairs that may alter the therapeutic outcomes in COVID-19 patients are presented. The major drug variant pairs that associated with variations in clinical efficacy include CQ/HCQ (CYP2C8, CYP2D6, ACE2, and HO-1); azithromycin (ABCB1); LPV/r (SLCO1B1, ABCB1, ABCC2 and CYP3A); NVP (ABCC10); oseltamivir (CES1 and ABCB1); remdesivir (CYP2C8, CYP2D6, CYP3A4, and OATP1B1); anakinra (IL-1a); and TCZ (IL6R and FCGR3A). The major drug variant pairs that associated with variations in adverse effects include CQ/HCQ (G6PD; hemolysis and ABCA4; retinopathy), ATV (MDR1 and UGT1A1*28; hyperbilirubinemia; and APOA5; dyslipidemia), NVP (HLA-DRB1*01, HLA-B*3505 and CYP2B6; skin rash and MDR1; hepatotoxicity), and EFV (CYP2B6; depression and suicidal tendencies).
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Gordeuk VR, Shah BN, Zhang X, Thuma PE, Zulu S, Moono R, Reading NS, Song J, Zhang Y, Nouraie M, Campbell A, Minniti CP, Rana SR, Darbari DS, Kato GJ, Niu M, Castro OL, Machado R, Gladwin MT, Prchal JT. The CYB5R3 c .350C>G and G6PD A alleles modify severity of anemia in malaria and sickle cell disease. Am J Hematol 2020; 95:1269-1279. [PMID: 32697331 PMCID: PMC8095369 DOI: 10.1002/ajh.25941] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 07/08/2020] [Indexed: 12/18/2022]
Abstract
Genetic modifiers of anemia in Plasmodium falciparum infection and sickle cell disease (SCD) are not fully known. Both conditions are associated with oxidative stress, hemolysis and anemia. The CYB5R3 gene encodes cytochrome b5 reductase 3, which converts methemoglobin to hemoglobin through oxidation of NADH. CYB5R3c.350C > G encoding CYB5R3T117S , the most frequent recognized African-specific polymorphism, does not have known functional significance, but its high allele frequency (23% in African Americans) suggests a selection advantage. Glucose-6-phosphate dehydrogenase (G6PD) is essential for protection from oxidants; its African-polymorphic X-linked A+ and A- alleles, and other variants with reduced activity, coincide with endemic malaria distribution, suggesting protection from lethal infection. We examined the association of CYB5R3c.350C > G with severe anemia (hemoglobin <5 g/dL) in the context of G6PD A+ and A- status among 165 Zambian children with malaria. CYB5R3c.350C > G offered protection against severe malarial anemia in children without G6PD deficiency (G6PD wild type or A+/A- heterozygotes) (odds ratio 0.29, P = .022) but not in G6PD A+ or A- hemizygotes/homozygotes. We also examined the relationship of CYB5R3c.350C > G with hemoglobin concentration among 267 children and 321 adults and adolescents with SCD in the US and UK and found higher hemoglobin in SCD patients without G6PD deficiency (β = 0.29, P = .022 children; β = 0.33, P = .004 adults). Functional studies in SCD erythrocytes revealed mildly lower activity of native CYB5R3T117S compared to wildtype CYB5R3 and higher NADH/NAD+ ratios. In conclusion, CYB5R3c.350C > G appears to ameliorate anemia severity in malaria and SCD patients without G6PD deficiency, possibly accounting for CYB5R3c.350C > G selection and its high prevalence.
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Affiliation(s)
- Victor R. Gordeuk
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Binal N. Shah
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Xu Zhang
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | | | | | | | | | - Jihyun Song
- University of Utah and ARUP Laboratories, Salt Lake City, Utah
| | - Yingze Zhang
- Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Mehdi Nouraie
- Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Andrew Campbell
- Children’s National Medical Center, Washington, District of Columbia
| | - Caterina P. Minniti
- Center for Sickle Cell Disease, Montefiore Medical Center, New York, New York
| | - Sohail R. Rana
- Department of Pediatrics and Child Health, Howard University Hospital, Washington, District of Columbia
| | | | | | - Mei Niu
- Center for Sickle Cell Disease, Howard University, Washington, District of Columbia
| | - Oswaldo L. Castro
- Center for Sickle Cell Disease, Howard University, Washington, District of Columbia
| | | | - Mark T. Gladwin
- Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
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Nouraie M, Darbari DS, Rana S, Minniti CP, Castro OL, Luchtman‐Jones L, Sable C, Dham N, Kato GJ, Gladwin MT, Ensing G, Arteta M, Campbell A, Taylor JG, Nekhai S, Gordeuk VR. Tricuspid regurgitation velocity and other biomarkers of mortality in children, adolescents and young adults with sickle cell disease in the United States: The PUSH study. Am J Hematol 2020; 95:766-774. [PMID: 32243618 DOI: 10.1002/ajh.25799] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 03/25/2020] [Indexed: 01/03/2023]
Abstract
In the US, mortality in sickle cell disease (SCD) increases after age 18-20 years. Biomarkers of mortality risk can identify patients who need intensive follow-up and early or novel interventions. We prospectively enrolled 510 SCD patients aged 3-20 years into an observational study in 2006-2010 and followed 497 patients for a median of 88 months (range 1-105). We hypothesized that elevated pulmonary artery systolic pressure as reflected in tricuspid regurgitation velocity (TRV) would be associated with mortality. Estimated survival to 18 years was 99% and to 25 years, 94%. Causes of death were known in seven of 10 patients: stroke in four (hemorrhagic two, infarctive one, unspecified one), multiorgan failure one, parvovirus B19 infection one, sudden death one. Baseline TRV ≥2.7 m/second (>2 SD above the mean in age-matched and gender-matched non-SCD controls) was observed in 20.0% of patients who died vs 4.6% of those who survived (P = .012 by the log rank test for equality of survival). The baseline variable most strongly associated with an elevated TRV was a high hemolytic rate. Additional biomarkers associated with mortality were ferritin ≥2000 μg/L (observed in 60% of patients who died vs 7.8% of survivors, P < .001), forced expiratory volume in 1 minute to forced vital capacity ratio (FEV1/FVC) <0.80 (71.4% of patients who died vs 18.8% of survivors, P < .001), and neutrophil count ≥10x109 /L (30.0% of patients who died vs 7.9% of survivors, P = .018). In SCD children, adolescents and young adults, steady-state elevations of TRV, ferritin and neutrophils and a low FEV1/FVC ratio may be biomarkers associated with increased risk of death.
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Affiliation(s)
- Mehdi Nouraie
- University of Pittsburgh Pittsburgh Pennsylvania USA
| | | | - Sohail Rana
- Center for Sickle Cell DiseaseHoward University Washington District of Columbia USA
| | - Caterina P. Minniti
- Montfiore Medical Center, Einstein College of Medicine New York New York USA
| | - Oswaldo L. Castro
- Center for Sickle Cell DiseaseHoward University Washington District of Columbia USA
| | - Lori Luchtman‐Jones
- Cincinnati Children's Hospital Medical Center/University of Cincinnati College of Medicine Cincinnati Ohio USA
| | - Craig Sable
- Children's National Medical Center Washington District of Columbia USA
| | - Niti Dham
- Children's National Medical Center Washington District of Columbia USA
| | | | | | | | | | - Andrew Campbell
- Children's National Medical Center Washington District of Columbia USA
| | - James G. Taylor
- Center for Sickle Cell DiseaseHoward University Washington District of Columbia USA
| | - Sergei Nekhai
- Center for Sickle Cell DiseaseHoward University Washington District of Columbia USA
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Leopold SJ, Watson JA, Jeeyapant A, Simpson JA, Phu NH, Hien TT, Day NPJ, Dondorp AM, White NJ. Investigating causal pathways in severe falciparum malaria: A pooled retrospective analysis of clinical studies. PLoS Med 2019; 16:e1002858. [PMID: 31442221 PMCID: PMC6707545 DOI: 10.1371/journal.pmed.1002858] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 07/25/2019] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Severe falciparum malaria is a medical emergency characterised by potentially lethal vital organ dysfunction. Patient fatality rates even with parenteral artesunate treatment remain high. Despite considerable research into adjuvant therapies targeting organ and tissue dysfunction, none have shown efficacy apart from renal replacement therapy. Understanding the causal contributions of clinical and laboratory abnormalities to mortality is essential for the design and evaluation of novel therapeutic interventions. METHODS AND FINDINGS We used a structural model causal inference approach to investigate causal relationships between epidemiological, laboratory, and clinical variables in patients with severe falciparum malaria enrolled in clinical trials and their in-hospital mortality. Under this causal model, we analysed records from 9,040 hospitalised children (0-12 years, n = 5,635) and adults (n = 3,405, 12-87 years) with severe falciparum malaria from 15 countries in Africa and Asia who were studied prospectively over the past 35 years. On admission, patient covariates associated with increased in-hospital mortality were severity of acidosis (odds ratio [OR] 2.10 for a 7-mEq/L increase in base deficit [95% CI 1.93-2.28]), renal impairment (OR 1.71 for a 2-fold increase in blood urea nitrogen [95% CI 1.58, 1.86]), coma (OR 3.59 [95% CI 3.07-4.21]), seizures (OR 1.40 [95% CI 1.16-1.68]), shock (OR 1.51 [95% CI 1.14-1.99]), and presumed pulmonary oedema (OR 1.58 [95% CI 1.04-2.39]). Lower in-hospital mortality was associated with moderate anaemia (OR 0.87 for a decrease of 10 percentage points in haematocrit [95% CI 0.80-0.95]). Circulating parasite density was not associated with mortality (OR 1.02 for a 6-fold increase [95% CI 0.94-1.11]), so the pathological effects of parasitaemia appear to be mediated entirely by the downstream effects of sequestration. Treatment with an artemisinin derivative decreased mortality compared with quinine (OR 0.64 [95% CI 0.56-0.74]). These estimates were consistent across children and adults (mainly representing African and Asian patients, respectively). Using inverse probability weighting, transfusion was not estimated to be beneficial in children with admission haematocrit values between 15% and 25% (OR 0.99 [95% CI 0.97-1.02]). Except for the effects of artemisinin treatment and transfusion, causal interpretations of these estimates could be biased by unmeasured confounding from severe bacterial sepsis, immunity, and duration of illness. CONCLUSION These data suggest that moderate anaemia is associated with a reduced risk of death in severe falciparum malaria. This is possibly a direct causal association. The severe anaemia threshold criteria for a definition of severe falciparum malaria should be reconsidered.
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Affiliation(s)
- Stije J. Leopold
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - James A. Watson
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Atthanee Jeeyapant
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Julie A. Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia
| | - Nguyen H. Phu
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Tran T. Hien
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Nicholas P. J. Day
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Arjen M. Dondorp
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Nicholas J. White
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
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Biological impact of α genes, β haplotypes, and G6PD activity in sickle cell anemia at baseline and with hydroxyurea. Blood Adv 2019; 2:626-637. [PMID: 29555644 DOI: 10.1182/bloodadvances.2017014555] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 02/20/2018] [Indexed: 12/17/2022] Open
Abstract
Sickle cell anemia (SCA), albeit monogenic, has heterogeneous phenotypic expression, mainly related to the level of hemoglobin F (HbF). No large cohort studies have ever compared biological parameters in patients with major β-globin haplotypes; ie, Senegal (SEN), Benin (BEN), and Bantu/Central African Republic (CAR). The aim of this study was to evaluate the biological impact of α genes, β haplotypes, and glucose-6-phosphate dehydrogenase (G6PD) activity at baseline and with hydroxyurea (HU). Homozygous HbS patients from the Créteil pediatric cohort with available α-gene and β-haplotype data were included (n = 580; 301 females and 279 males) in this retrospective study. Homozygous β-haplotype patients represented 74% of cases (37.4% CAR/CAR, 24.3% BEN/BEN, and 12.1% SEN/SEN). HU was given to 168 cohort SCA children. Hematological parameters were recorded when HbF was maximal, and changes (ΔHU-T0) were calculated. At baseline, CAR-haplotype and α-gene numbers were independently and negatively correlated with Hb and positively correlated with lactate dehydrogenase. HbF was negatively correlated with CAR-haplotype numbers and positively with BEN- and SEN-haplotype numbers. The BCL11A/rs1427407 "T" allele, which is favorable for HbF expression, was positively correlated with BEN- and negatively correlated with CAR-haplotype numbers. With HU treatment, Δ and HbF values were positively correlated with the BEN-haplotype number. BEN/BEN patients had higher HbF and Hb levels than CAR/CAR and SEN/SEN patients. In conclusion, we show that BEN/BEN patients have the best response on HU and suggest that this could be related to the higher prevalence of the favorable BCL11A/rs1427407/T/allele for HbF expression in these patients.
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Kalpatthi R, Novelli EM. Measuring success: utility of biomarkers in sickle cell disease clinical trials and care. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2018; 2018:482-492. [PMID: 30504349 PMCID: PMC6246014 DOI: 10.1182/asheducation-2018.1.482] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Progress in the care of sickle cell disease (SCD) has been hampered by the extreme complexity of the SCD phenotype despite its monogenic inheritance. While epidemiological studies have identified clinical biomarkers of disease severity, with a few exceptions, these have not been routinely incorporated in clinical care algorithms. Furthermore, existing biomarkers have been poorly apt at providing objective parameters to diagnose sickle cell crisis, the hallmark, acute complication of SCD. The repercussions of these diagnostic limitations are reflected in suboptimal care and scarcity of adequate outcome measures for clinical research. Recent progress in molecular and imaging diagnostics has heralded a new era of personalized medicine in SCD. Precision medicine strategies are particularly timely, since molecular therapeutics are finally on the horizon. This chapter will summarize the existing evidence and promising data on biomarkers for clinical care and research in SCD.
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Affiliation(s)
- Ram Kalpatthi
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Children’s Hospital of Pittsburgh, Pittsburgh, PA; and
| | - Enrico M. Novelli
- Division of Hematology/Oncology and UPMC Heart, Lung and Blood Vascular Medicine Institute, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
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Lee N, Makani J, Tluway F, Makubi A, Armitage AE, Pasricha SR, Drakesmith H, Prentice AM, Cox SE. Decreased Hepcidin Levels Are Associated with Low Steady-state Hemoglobin in Children With Sickle Cell Disease in Tanzania. EBioMedicine 2018; 34:158-164. [PMID: 30056060 PMCID: PMC6116423 DOI: 10.1016/j.ebiom.2018.07.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 07/17/2018] [Accepted: 07/17/2018] [Indexed: 01/17/2023] Open
Abstract
Background The contribution of hepcidin as a regulator of iron metabolism & erythropoiesis on the severity of anemia in sickle cell disease (SCD) remains poorly characterized, especially in Sub-Saharan African populations. The aims of the study were to determine if hepcidin is associated with severity of steady-state anemia in SCD and to investigate factors associated with hepcidin and anemia in SCD. Methods Archived samples from 199 Tanzanian children, 56% boys aged 3–18 with laboratory-confirmed SCD were analysed based on recorded averaged steady-state hemoglobin (ASSH) quartiles (lowest vs. highest). Univariable and multivariable logistic regression was used to assess associations with ASSH quartiles. Findings In univariable analysis, hepcidin <5·5 ng/mL was associated with increased odds of being in the lowest ASSH quartile (OR 2·20; 95%CI 1·2–3·93) but which was limited to girls (OR 4·85, 95%CI 1·79–13·09, p = .046 for interaction). In multivariable analyses including either reticulocyte percentage or erythropoietin, lower hepcidin remained significantly associated with lowest ASSH quartile, although the hepcidin-sex interaction no longer reached statistical significance. No associations with ASSH quartile were observed for markers of inflammation, hemolysis or potential iron markers except for microcytosis, associated with higher ASSH, but which was confounded by reticulocyte percentage and alpha-thalassaemia status. Interpretation Hepcidin is lower in more severely anaemic children with SCD independent of inflammation or markers of erythropoiesis. Funding Funding sources include The Wellcome Trust (080025, 095009, 094780 & 070114), MRC-UK (MC-A760-5QX00), NIHR Oxford Biomedical Research Centre, and the Bill and Melinda Gates Foundation (“Hepcidin and Iron in Global Health”, OPP1055865). Low hepcidin levels are associated with severe anemia independent of markers of erythropoiesis and inflammation. Low serum ferritin is present in some children but is not associated with severe anemia. Although iron markers remain difficult to interpret in sickle cell disease, hepcidin levels were mostly below levels that would be expected to inhibit iron absorption and recycling.
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Affiliation(s)
- Nathaniel Lee
- School of Tropical Medicine & Global Health, Nagasaki University, Nagasaki, Japan
| | - Julie Makani
- Sickle Cell Programme, Muhimbili University of Health & Allied Sciences, Dar-es-Salaam, Tanzania; Department of Haematology & Blood Transfusion, Muhimbili University of Health and Allied Sciences, Dar-es-Salaam, Tanzania
| | - Furahini Tluway
- Sickle Cell Programme, Muhimbili University of Health & Allied Sciences, Dar-es-Salaam, Tanzania
| | - Abel Makubi
- Department of Haematology & Blood Transfusion, Muhimbili University of Health and Allied Sciences, Dar-es-Salaam, Tanzania
| | - Andrew E Armitage
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, UK
| | - Sant-Rayn Pasricha
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, UK
| | - Hal Drakesmith
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, UK
| | | | - Sharon E Cox
- School of Tropical Medicine & Global Health, Nagasaki University, Nagasaki, Japan; London School of Hygiene and Tropical Medicine, London, UK.
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Significantly elevated foetal haemoglobin levels in individuals with glucose 6-phosphate dehydrogenase disease and/or sickle cell trait: a cross-sectional study in Cape Coast, Ghana. BMC HEMATOLOGY 2017; 17:16. [PMID: 29021902 PMCID: PMC5613503 DOI: 10.1186/s12878-017-0088-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 09/15/2017] [Indexed: 12/02/2022]
Abstract
Background Previously published data have demonstrated that sickle red blood cells produce twice as much reactive oxygen species (ROS) suggesting that co-inheritance of sickle cell disease (SCD) and glucose 6-phosphate dehydrogenase (G6PD) enzymopathy could lead to more severe anaemia during sickling crises. Elevated foetal haemoglobin (Hb F) levels have been shown to have positive modulatory effects on sickling crises and disease outcomes. This study sought to assess how inheritance of G6PD enzymopathy affects the level of Hb F and haemoglobin concentration in adults in steady state. Methods This cross-sectional study selected 100 out-patients (41 males and 59 females) visiting the University of Cape Coast hospital, between January, 2016 and May, 2016. Cellulose acetate electrophoresis (pH 8.2–8.6), methaemoglobin reductase test, modified Betke alkaline denaturation methods were used to investigate haemoglobin variants, qualitative G6PD status, and %Hb F levels in venous blood samples drawn from these participants. Data was analysed with GraphPad Prism 6 and SPSS and significance set at p < 0.05. Results Forty one percent of the participants demonstrated qualitative G6PD enzymopathy whereas only 10% demonstrated Hb AS type (Sickle cell trait, SCT). 5% of the participants co-inherited SCT and G6PD enzymopathy. %Hb F levels in G6PD deficient males was significantly higher than in G6PD deficient females [(p = 0.0003, 2.696% (males) vs 1.975% (females)], although the %Hb F levels was comparable in non-G6PD deficient individuals. %Hb F levels were significantly elevated in males with SCT only (p < 0.05), or G6PD enzymopathy only (p < 0.0001), or SCT + G6PD enzymopathy (p < 0.0001) compared to males with none of these pathologies even though their respective haemoglobin levels were comparable. Male participants with G6PD enzymopathy + SCT co-inheritance had significantly elevated %Hb F when compared to their counterparts with only G6PD enzymopathy (p < 0.001). Male gender [(p = 0.001, OR: 6.912 (2.277–20.984)] partial defective G6PD enzyme [(p = 0.00, OR: 7.567E8 (8.443E7–6.782E9)] SCT [(p = 0.026, OR: 4.625 (1.196–17.881)] were factors associated with raised %Hb F levels ≥2.5. Conclusion The inheritance of G6PD defect and/or SCT significantly elevate %Hb F levels in the steady state even though haemoglobin levels are not affected.
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Quinn CT. Minireview: Clinical severity in sickle cell disease: the challenges of definition and prognostication. Exp Biol Med (Maywood) 2016; 241:679-88. [PMID: 27013545 PMCID: PMC4871738 DOI: 10.1177/1535370216640385] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Sickle cell disease (SCD) is a monogenic, yet highly phenotypically variable disease with multisystem pathology. This manuscript provides an overview of many of the known determinants, modifiers, and correlates of disease severity in SCD. Despite this wealth of data, modeling the variable and multisystem pathology of SCD continues to be difficult. The current status of prediction of specific adverse outcomes and global disease severity in SCD is also reviewed, highlighting recent successes and ongoing challenges.
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Affiliation(s)
- Charles T Quinn
- Division of Hematology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45220, USA
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Coates TD. Physiology and pathophysiology of iron in hemoglobin-associated diseases. Free Radic Biol Med 2014; 72:23-40. [PMID: 24726864 PMCID: PMC4940047 DOI: 10.1016/j.freeradbiomed.2014.03.039] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 03/26/2014] [Accepted: 03/27/2014] [Indexed: 01/19/2023]
Abstract
Iron overload and iron toxicity, whether because of increased absorption or iron loading from repeated transfusions, can be major causes of morbidity and mortality in a number of chronic anemias. Significant advances have been made in our understanding of iron homeostasis over the past decade. At the same time, advances in magnetic resonance imaging have allowed clinicians to monitor and quantify iron concentrations noninvasively in specific organs. Furthermore, effective iron chelators are now available, including preparations that can be taken orally. This has resulted in substantial improvement in mortality and morbidity for patients with severe chronic iron overload. This paper reviews the key points of iron homeostasis and attempts to place clinical observations in patients with transfusional iron overload in context with the current understanding of iron homeostasis in humans.
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Affiliation(s)
- Thomas D Coates
- Children׳s Center for Cancer and Blood Diseases, Children׳s Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA 90027, USA.
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Cox SE, Makani J, Soka D, L'Esperence VS, Kija E, Dominguez-Salas P, Newton CRJ, Birch AA, Prentice AM, Kirkham FJ. Haptoglobin, alpha-thalassaemia and glucose-6-phosphate dehydrogenase polymorphisms and risk of abnormal transcranial Doppler among patients with sickle cell anaemia in Tanzania. Br J Haematol 2014; 165:699-706. [PMID: 24666344 PMCID: PMC4154124 DOI: 10.1111/bjh.12791] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 01/05/2014] [Indexed: 02/04/2023]
Abstract
Transcranial Doppler ultrasonography measures cerebral blood flow velocity (CBFv) of basal intracranial vessels and is used clinically to detect stroke risk in children with sickle cell anaemia (SCA). Co‐inheritance in SCA of alpha‐thalassaemia and glucose‐6‐phosphate dehydrogenase (G6PD) polymorphisms is reported to associate with high CBFv and/or risk of stroke. The effect of a common functional polymorphism of haptoglobin (HP) is unknown. We investigated the effect of co‐inheritance of these polymorphisms on CBFv in 601 stroke‐free Tanzanian SCA patients aged <24 years. Homozygosity for alpha‐thalassaemia 3·7 deletion was significantly associated with reduced mean CBFv compared to wild‐type (β‐coefficient −16·1 cm/s, P = 0·002) adjusted for age and survey year. Inheritance of 1 or 2 alpha‐thalassaemia deletions was associated with decreased risk of abnormally high CBFv, compared to published data from Kenyan healthy control children (Relative risk ratio [RRR] = 0·53 [95% confidence interval (CI):0·35–0·8] & RRR = 0·43 [95% CI:0·23–0·78]), and reduced risk of abnormally low CBFv for 1 deletion only (RRR = 0·38 [95% CI:0·17–0·83]). No effects were observed for G6PD or HP polymorphisms. This is the first report of the effects of co‐inheritance of common polymorphisms, including the HP polymorphism, on CBFv in SCA patients resident in Africa and confirms the importance of alpha‐thalassaemia in reducing risk of abnormal CBFv.
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Affiliation(s)
- Sharon E Cox
- MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, UK; Muhimbili Wellcome Programme, Muhimbili University of Health & Allied Sciences, Dar es Salaam, Tanzania
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Hematological and Genetic Predictors of Daytime Hemoglobin Saturation in Tanzanian Children with and without Sickle Cell Anemia. ISRN HEMATOLOGY 2013; 2013:472909. [PMID: 23691341 PMCID: PMC3649307 DOI: 10.1155/2013/472909] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 03/07/2013] [Indexed: 12/27/2022]
Abstract
Low hemoglobin oxygen saturation (SpO2) is common in Sickle Cell Anemia (SCA) and associated with complications including stroke, although determinants remain unknown. We investigated potential hematological, genetic, and nutritional predictors of daytime SpO2 in Tanzanian children with SCA and compared them with non-SCA controls. Steady-state resting pulse oximetry, full blood count, transferrin saturation, and clinical chemistry were measured. Median daytime SpO2 was 97% (IQ range 94–99%) in SCA (N = 458), lower (P < 0.0001) than non-SCA (median 99%, IQ range 98–100%; N = 394). Within SCA, associations with SpO2 were observed for hematological variables, transferrin saturation, body-mass-index z-score, hemoglobin F (HbF%), genotypes, and hemolytic markers; mean cell hemoglobin (MCH) explained most variability (P < 0.001, Adj r2 = 0.09). In non-SCA only age correlated with SpO2. α-thalassemia 3.7 deletion highly correlated with decreased MCH (Pearson correlation coefficient −0.60, P < 0.0001). In multivariable models, lower SpO2 correlated with higher MCH (β-coefficient −0.32, P < 0.001) or with decreased copies of α-thalassemia 3.7 deletion (β-coefficient 1.1, P < 0.001), and independently in both models with lower HbF% (β-coefficient 0.15, P < 0.001) and Glucose-6-Phosphate Dehydrogenase genotype (β-coefficient −1.12, P = 0.012). This study provides evidence to support the hypothesis that effects on red cell rheology are important in determining SpO2 in children with SCA. Potential mechanisms and implications are discussed.
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Minniti CP, Taylor JG, Hildesheim M, O'Neal P, Wilson J, Castro O, Gordeuk VR, Kato GJ. Laboratory and echocardiography markers in sickle cell patients with leg ulcers. Am J Hematol 2011; 86:705-8. [PMID: 21630312 PMCID: PMC3245712 DOI: 10.1002/ajh.22065] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/15/2011] [Accepted: 04/19/2011] [Indexed: 10/18/2022]
Abstract
Chronic leg ulcers are a debilitating complication of sickle cell disease, associated with increased morbidity and perhaps mortality that affect 8 to 50% of patients. We evaluated the characteristics of SCD patients with a history of leg ulceration, including hemolytic rate, estimated pulmonary artery systolic pressure, and other parameters in a cohort of 505 adults with SCD. Ninety four subjects (18%) had either active ulcers at enrollment or history of leg ulceration. Patients affected were older and predominantly had homozygous SS, lower body mass index, and pulse oximetry, higher tricuspid regurgitation velocities, markers of hemolysis, serum uric acid and serum NT-proBNP, when compared to subjects without such history. In this prospective cohort of adults with SCD, we confirm that leg ulcers are still frequent and are associated with elevated TRVand markers of hemolysis. We describe a novel association of leg ulcer with hyperuricemia and oxygen desaturation and suggest potential implications for uric acid as a marker of vascular dysfunction.
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Affiliation(s)
- Caterina P Minniti
- Cardiovascular and Pulmonary Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Genetic association analysis highlights new loci that modulate hematological trait variation in Caucasians and African Americans. Hum Genet 2010; 129:307-17. [PMID: 21153663 DOI: 10.1007/s00439-010-0925-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 11/25/2010] [Indexed: 01/03/2023]
Abstract
Red blood cell, white blood cell, and platelet measures, including their count, sub-type and volume, are important diagnostic and prognostic clinical parameters for several human diseases. To identify novel loci associated with hematological traits, and compare the architecture of these phenotypes between ethnic groups, the CARe Project genotyped 49,094 single nucleotide polymorphisms (SNPs) that capture variation in ~2,100 candidate genes in DNA of 23,439 Caucasians and 7,112 African Americans from five population-based cohorts. We found strong novel associations between erythrocyte phenotypes and the glucose-6 phosphate dehydrogenase (G6PD) A-allele in African Americans (rs1050828, P<2.0×10(-13), T-allele associated with lower red blood cell count, hemoglobin, and hematocrit, and higher mean corpuscular volume), and between platelet count and a SNP at the tropomyosin-4 (TPM4) locus (rs8109288, P=3.0×10(-7) in Caucasians; P=3.0×10(-7) in African Americans, T-allele associated with lower platelet count). We strongly replicated many genetic associations to blood cell phenotypes previously established in Caucasians. A common variant of the α-globin (HBA2-HBA1) locus was associated with red blood cell traits in African Americans, but not in Caucasians (rs1211375, P<7×10(-8), A-allele associated with lower hemoglobin, mean corpuscular hemoglobin, and mean corpuscular volume). Our results show similarities but also differences in the genetic regulation of hematological traits in European- and African-derived populations, and highlight the role of natural selection in shaping these differences.
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