Acute triiodothyronine treatment and red blood cell sedimentation rate (ESR) in critically ill COVID-19 patients: A novel association?

Sepsis and septic shock result in impaired microcirculation and red blood cell rheology which lead to tissue hypoxia and multi-organ failure. Early administration of triiodothyronine prevents tissue hypoxia in experimental sepsis. In this context, a clinical trial was initiated to test the efficacy of acute triiodothyronine administration to combat tissue hypoxia in critically ill COVID19 patients. Here, we provide preliminary data from interim analysis of this study showing a novel acute effect of triiodothyronine on erythrocyte sedimentation rate which may have an important therapeutic impact on red blood cell rheology and tissue hypoxia in sepsis and particular in COVID19 critical illness. Trial registration: ClinicalTrials.gov, NCT04348513. Registered 16 April 2020, https://clinicaltrials.gov/ct2/show/NCT04348513

HbF-promoting polymorphisms may specifically reduce the residual risk of cerebral vasculopathy in SCA children with alpha-thalassemia

Sickle cell anemia (SCA) is a disease characterized by abnormal red blood cell rheology. Because of their effects on HbS polymerization and red blood cell deformability, alpha-thalassemia and the residual HbF level are known genetic modifiers of the disease. The aim of our study was to determine if the number of HbF quantitative trait loci (QTL) would also favor a specific sub-phenotype of SCA as it is the case for alpha-thalassemia. Our results confirmed that alpha-thalassemia protected from cerebral vasculopathy but increased the risk for frequent painful vaso-occlusive crises. We also showed that more HbF-QTL may provide an additional and specific protection against cerebral vasculopathy but only for children with alpha-thalassemia (-α/αα or -α/-α genotypes).

Red Cell Rheology Biomarkers to Assess Cure in Gene-Based Therapies

Introduction Red cell rheology is abnormal in sickle cell disease (SCD); red blood cells (RBC) are rigid, dense, and the sickle hemoglobin (HbS) polymerizes with deoxygenation. There are several devices commercially available and under development to assess RBC rheology. One is an oxygen gradient ektacytometer (Lorrca with Oxygenscan, RR Mechatronics) which measures RBC deformability under oxygenated conditions (EImax) and deoxygenated conditions (EImin), and the oxygen concentration at which deformability begins to worsen, point of sickling (PoS). A commercially available hematology analyzer, the ADVIA (Siemens), measures hemoglobin (Hb) by flow and colorimetric methods, permitting automated calculation of the percent dense red blood cells (%DRBC). Allogeneic hematopoietic stem cell transplant (alloHSCT) can provide a cure for SCD, and viable gene-based therapy options are under investigation to serve the many patients without a matched related donor. However, the level of HbS correction or functional Hb induction necessary to achieve a cure is still unknown. Clinical endpoints such as prevention of pain events are important, but it is possible to be pain free for several years while still experiencing organ damage. As gene-based therapy clinical trials move forward, we must assess the level of functional improvement beyond Hb profile and conventional clinical labs. We propose that the goal of any gene-based SCD therapy should be to normalize blood rheology to the level of an individual with sickle cell trait (HbAS), and that EImax, EImin, PoS, and %DRBC may be used to distinguish between HbAS and HbSS/Sβ0 genotypes. Methods Subjects: Blood samples were collected from 257 unique patients (17 HbAS, and 240 HbSS/Sβ0) under IRB-approved protocols at Texas Children's Hospital and University Medical Center Utrecht. Patients were 56% male, ages 9 months to 22 years. Some HbSS/Sβ0 subjects were on transfusion and hydroxyurea (HU) (Table 1). Fetal hemoglobin (HbF) levels ranged from 0-41%. Oxygen gradient ektacytometry: Blood collected in EDTA and standardized to a fixed RBC count was suspended in 5 mL polyvinylpyrrolidone at room temperature. 1.5 mL of the sample solution was injected into test cup. Each sample was run in duplicate. ADVIA: 250µL of blood collected in EDTA at room temperature was aspirated to measure the %DRBC, defined as the percentage of RBCs with a Hb concentration >1.11 mg/mL. Analysis: Patient characteristics were summarized using median with 25th and 75th percentiles, and frequency with percentage. Characteristics and labs were compared by group with t-test, Wilcoxon rank sum test, or Fisher's exact test. Receiver operating characteristics (ROC) analyses were performed to identify HbAS versus HbSS/Sβ0 for each biomarker. All analyses were performed using Stata 15. Results The EImin, EImax, PoS, and %DRBC differed significantly between the HbAS and HbSS/Sβ0 groups, despite including transfused, very young, and HU-treated samples in the HbSS/Sβ0 cohort (p<0.001, p=0.002, p<0.001, and p<0.001, respectively; Table 1). ROC analysis showed that a threshold Elmin greater than or equal to 0.453 identified HbAS with 94.12% sensitivity and 95.43% specificity. EImax greater or equal to 0.569 identified HbAS with 94.12% sensitivity and 81.57% specificity. PoS less than 21.38 mmHg identified HbAS with 93.87% sensitivity and 93.33% specificity. %DRBC less than 1.6% identified HbAS with 88.13% sensitivity and 88.00% specificity (Table 2). Conclusion Conventional laboratory testing may not be able to establish if gene-based therapy has achieved a cure. We propose to define a cure as achievement of an HbAS level of RBC quality in a gene-based therapy edited RBC population. We show that rheological biomarkers EImin, EImax, PoS, and %DRBC differ significantly between individuals with HbAS and HbSS/Sβ0 of all spectrums of severity and treatment regimens. Not only are the rheological biomarker values significantly different, but there is little to no overlap in ranges of values obtained from the different genotypes, even in heavily transfused HbSS patients, with HbS as low as 31%. EImin, EImax, PoS, and %DRBC functionally identify genotype with high sensitivity and specificity; we propose that they be used not to diagnose SCD, but to determine if a HbSS or HbSS/Sβ0 individual who has undergone successful gene-based therapy has achieved the RBC functionality of a HbAS individual. Disclosures van Beers: Novartis: Research Funding; Pfizer: Research Funding; Agios: Membership on an entity's Board of Directors or advisory committees, Research Funding; RR mechatronics: Research Funding. Wijk:Agios Pharmaceuticals Inc.: Research Funding; RR mechatronics: Research Funding. Rab:RR Mechatronics: Research Funding. Sheehan:Global Blood Therapeutics: Research Funding; Novartis: Research Funding; Emmaus: Research Funding.

Abstract WMP116: Thromboembolism in Atrial Fibrillation: Relationship to Leukocyte Gene Expression

Background: Atrial fibrillation (AF) is an important cause of stroke, for which anticoagulation provides substantial benefit. However, not all patients with AF will have a stroke. There remains uncertainty regarding factors that promote thromboembolism and stroke in patients with AF. In this study we examined differences in blood cell gene expression unique to AF in acute stroke to better understand factors important to atrial fibrillation thromboembolism in human stroke. Methods: Gene expression in blood was compared in acute stroke patients with AF to non-AF stroke and to controls without stroke. Blood was collected in PAXgene tubes, and leukocyte/platelet gene expression was measured by Affymetrix microarray. Differentially expressed genes were identified using ANOVA adjusted for age, sex and batch. Results: In the 184 patients studied, 40 were acute strokes with AF, 143 had non-AF acute stroke, and 116 were non-stroke controls. There were 43 genes unique to AF in patients with stroke, and 69 genes associated AF that were shared between AF stroke and controls (FDR<0.05, fold change>|1.5|). Functional analysis indicate acute stroke AF genes are associated with changes in the hematological system including blood cell rheology and leukocyte activation. In contrast non-stroke AF genes are associated cardiac hypertrophy and blood vessel injury. Conclusions: AF has differences in blood cell gene expression in acute stroke that may relate to risk of thromboembolism. Acute stroke patients with AF display changes in blood cell rheology and leukocyte activation; whereas non-stroke AF patients have changes in cardiac hypertrophy and vascular injury. These differences are important to understanding blood cell contribution to thrombus formation and stroke risk in patients with AF. Further study is required to assess the relationship of these gene changes to stroke risk and response to anticoagulation in patients with AF.