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Summary Sickle cell anaemia (SCA) patients display elevated levels of circulating pro‐inflammatory cytokines and endothelial activation markers compared to healthy peers. The impact of exercise on the pro‐inflammatory state in SCA remains unclear. This study aimed to characterize the whole‐blood transcriptome profile in response to an acute bout of exercise in paediatric SCA patients. Twenty‐three SCA participants (13 ± 3 years, 52% girls) and 17 healthy controls (14 ± 3 years, 29% girls) performed eight 2‐min bouts of cycle ergometry interspersed with 1‐min rest intervals. Whole‐blood transcriptome profile (RNA‐seq) was performed before and after exercise. At baseline, gene pathways associated with gas transport in erythrocytes were up‐regulated in SCA patients compared to controls. Following exercise, gene pathways associated with innate immunity were altered in both groups. Interaction analyses revealed 160 annotated genes (101 up‐ and 59 down‐regulated) that differentially altered by exercise in SCA patients. Moreover, genes that exhibited a blunted response to exercise in SCA patients were enriched in the IL‐17 signalling pathway, suggesting an impaired innate immune response to exercise. This data will contribute to the development of evidence‐based exercise prescription guidelines for this patient population. [ABSTRACT FROM AUTHOR]

Transfusional iron overload represents a substantial challenge in the management of patients with sickle cell disease ( SCD) who receive chronic or episodic red blood cell transfusions. Iron-induced cardiomyopathy is a leading cause of death in other chronically transfused populations but rarely seen in SCD. Study objectives were to: (i) examine the extent of myocardial and hepatic siderosis using magnetic resonance imaging ( MRI) in chronically transfused SCD patients, and (ii) evaluate the relationship between long-term (over the 5 years prior to enrolment) mean serum ferritin ( MSF), spot-ferritin values and liver iron content ( LIC) measured using MRI and liver biopsy. Thirty-two SCD patients (median age 15 years) with transfusional iron overload were recruited from two U.S. institutions. Long-term MSF and spot-ferritin values significantly correlated with LIC by MRI-R2* ( r = 0·77, P < 0·001; r = 0·82, P < 0·001, respectively). LIC by MRI-R2* had strong positive correlation with LIC by liver biopsy ( r = 0·98, P < 0·001) but modest inverse correlation with cardiac MRI-T2* ( r = −0·41, P = 0·02). Moderate to severe transfusional iron overload in SCD was not associated with aberrations in other measures of cardiac function based on echocardiogram or serum biomarkers. Our results suggest that SCD patients receiving chronic transfusions may not demonstrate significant cardiac iron loading irrespective of ferritin trends, LIC and erythropoiesis suppression. [ABSTRACT FROM AUTHOR]

Although individuals with sickle cell anaemia (SCA) have elevated baseline inflammation and endothelial activation, the acute phase response to maximal exercise has not been evaluated among children with SCA. We measured the acute phase response to maximal exercise testing for soluble vascular cell adhesion molecule (sVCAM) as well as interleukin 6 (IL6), total white blood cell (WBC) count, C-reactive protein (CRP) and D-dimer in a cohort of children with SCA and matched controls at baseline, immediately after, and 30, 60 and 120 min following exercise. Despite higher baseline levels of all biomarkers except CRP, the acute phase response from baseline to immediately after exercise was significantly greater in subjects versus controls for CRP (2.1 vs. 0.2 mg/l, P = 0.02) and D-dimer (160 vs. 10 µg/l, P < 0.01) only. Similar between-group trends were observed over time for all biomarkers, including sVCAM, IL6, total WBC, CRP and D-dimer. Lower fitness, defined by peak oxygen consumption (VO2), was independently associated with greater acute phase responses to exercise for sVCAM. Our results suggest maximal exercise may not be associated with any greater escalation of endothelial activation or inflammation in SCA and provide preliminary biomarker evidence for the safety of brief, high-intensity physical exertion in children with SCA. [ABSTRACT FROM AUTHOR]

Physiologic contributors to reduced exercise capacity in individuals with sickle cell anemia (SCA) are not well understood. The objective of this study was to characterize the cardiopulmonary response to maximal cardiopulmonary exercise testing (CPET) and determine factors associated with reduced exercise capacity among children and young adults with SCA. A cross-sectional cohort of 60 children and young adults (mean 15.1 ± 3.4 years) with hemoglobin SS or S/β0 thalassemia and 30 matched controls (mean 14.6 ± 3.5 years) without SCA or sickle cell trait underwent maximal CPET by a graded, symptom-limited cycle ergometry protocol with breath-by-breath, gas exchange analysis. Compared to controls without SCA, subjects with SCA demonstrated significantly lower peak VO2 (26.9 ± 6.9 vs. 37.0 ± 9.2 mL/kg/min, P < 0.001). Subjects demonstrated slower oxygen uptake (ΔVO2/ΔWR, 9 ± 2 vs. 12 ± 2 mL/min/watt, P < 0.001) and lower oxygen pulse (ΔVO2/ΔHR, 12 ± 4 vs. 20 ± 7 mL/beat, P < 0.001) as well as reduced oxygen uptake efficiency (Δ VE/ΔVO2, 42 ± 8 vs. 32 ± 5, P < 0.001) and ventilation efficiency (Δ VE/ΔVCO2, 30.3 ± 3.7 vs. 27.3 ± 2.5, P < 0.001) during CPET. Peak VO2 remained significantly lower in subjects with SCA after adjusting for age, sex, body mass index (BMI), and hemoglobin, which were independent predictors of peak VO2 for subjects with SCA. In the largest study to date using maximal CPET in SCA, we demonstrate that children and young adults with SCA have reduced exercise capacity attributable to factors independent of anemia. Complex derangements in gas exchange and oxygen uptake during maximal exercise are common in this population. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a population pharmacokinetic (PK) model sufficient to describe hydroxyurea (HU) concentrations in serum and urine following oral drug administration in pediatric patients with sickle cell disease. Additionally, the measured hydroxyurea concentrations for particular sampling time were correlated with exposure measures (AUC) to find the most predictive relationship. Hydroxyurea concentrations were determined in 21 subjects. Using a population nonlinear mixed-effect modeling, the HU PK was best described by a one-compartment model with two elimination pathways (metabolic and renal) and a transit compartment absorption. The typical mean absorption time was 0.222 hour. The typical apparent volume of distribution was 21.8 L and the apparent systemic clearance was 6.88 L/h for an average weight patient of 30.7 kg. The 50% of the HU dose was renally excreted. Linear correlations were apparent between the plasma HU concentration at 1, 1.5, 2, 4, and 6 hours post-dose and AUC with the most significant (R2 = 0.71) observed at 1.5 hours. A population PK model was successful in describing HU disposition in plasma and urine. Data from the model also demonstrated that HU plasma concentrations at 1.5 hours after an oral dose of the drug were highly predictive of systemic drug exposure. [ABSTRACT FROM AUTHOR]

Red blood cell ( RBC) transfusions can be life-sustaining in chronic inherited anaemias, such as thalassaemia, and the indications for blood transfusions in patients with sickle cell disease continue to expand. Complications of transfusions, such as allosensitization, can create significant medical challenges in the management of patients with haemoglobinopathies. This review summarizes key findings from the medical literature related to alloimmunization in haemoglobinopathies and examines potential measures to mitigate these risks. Areas where future studies are needed are also addressed. [ABSTRACT FROM AUTHOR]

Summary: We examined heart rate variability (HRV) during exercise testing in 20 children with sickle cell anaemia (SCA) and 12 controls. Subjects achieved lower median HRV at peak exercise [standard deviation of R‐wave to R‐wave intervals (SDNN), 2·3 vs 2·9 ms, P = 0·027; logarithmic transformation of high frequency power (lnHF), 0·9 vs 1·3 ln(ms2), P = 0·047] and had lower post‐exercise HRV across minute‐by‐minute analysis of recovery. After adjustment for haemoglobin, fitness and SCA status, subjects had lower HRV at the end of recovery with differences increasing as baseline HRV increased. Further investigation of HRV and exercise safety in SCA is warranted. [ABSTRACT FROM AUTHOR]

Summary: We used near‐infrared spectroscopy to examine tissue oxygenation (StO2) during exercise in 17 children and young adults with sickle cell anaemia (SCA) and 13 controls. Patients had lower cerebral StO2 at all exercise stages and demonstrated significantly greater decreases in cerebral StO2 later during exercise. Quadriceps StO2 increased similarly in patients and controls during early exercise, but decreases from baseline were greater in patients during later exercise. At similar workloads, patients demonstrated lower cerebral StO2 (69·2 ± 6·6 vs. 79·5 ± 5·3%, P < 0·001) and trended towards lower quadriceps StO2 (67·7 ± 9·0 vs. 73·2 ± 7·9%, P = 0·09). Further studies of tissue oxygenation during exercise in SCA are warranted. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To determine the factors associated with exercise capacity in adults with sickle cell disease (SCD) and its relationship to hospitalizations and mortality. Methods: A total of 223 participants in the Cooperative Study of Sickle Cell Disease (CSSCD) (64% female, 70% hemoglobin SS/Sβ0 thalassemia, mean age 43.3 ± 7.5 years) underwent maximal exercise testing using a treadmill protocol with a mean duration of 11.6 ± 5.2 minutes. Results: Female sex (β = −3.34, 95% CI [−1.80, −4.88], P < 0.001), older age (β = −0.14, 95% CI [−0.24, −0.04], P = 0.005), higher body mass index (β = −0.23, 95% CI [−0.37, −0.10]; P = 0.001), and lower hemoglobin (β = 0.56, 95% CI [0.08, 1.04], P = 0.02) were independently associated with lower fitness, while there was a trend with abnormal pulmonary function testing (β = −1.42, 95% CI [−2.92, 0.07]; P = 0.06). Lower percent‐predicted forced expiratory volume in 1 second (FEV1) was independently associated with lower fitness (β = 0.08, 95% CI [0.03, 0.13], P = 0.001). Genotype and hospitalization rates for pain and acute chest syndrome (ACS) prior to testing were not associated with exercise capacity. Baseline exercise capacity predicted neither future pain or ACS nor survival in our cohort. Adults with SCD tolerated maximal exercise testing. Conclusions: Prospective studies are needed to further evaluate the impact of regular exercise and improved fitness on clinical outcomes and mortality in SCD. [ABSTRACT FROM AUTHOR]

Background: Little is known about red blood cell (RBC) transfusion practices for children hospitalized for a sickle cell vaso-occlusive pain crisis (VOC). We hypothesized that transfusion would be associated with the development of acute chest syndrome (ACS), lower hemoglobin (Hb) concentration, and lack of hydroxyurea therapy.Study Design and Methods: This is a secondary analysis of all children admitted for a sickle cell pain crisis enrolled in the Magnesium in Crisis (MAGiC) randomized trial; all had HbSS or S-β0 thalassemia. ACS development and transfusion administration were prospectively collected during the parent trial. All Hb values during the hospitalization were recorded, as was parent report of child receiving hydroxyurea. Relative risks (RRs) of transfusion were compared between groups.Results: Of 204 enrolled children, 40 (19.6%) received a transfusion. Of the 30 children who developed ACS, 22 (73.3%) received transfusions compared to 18 of 174 (10.3%) without ACS: the RR of transfusion in children with ACS was 7.1 (95% confidence interval [CI], 4.4-11.5). Among those without ACS, the lowest Hb was most strongly associated with transfusions: RR was 3.1 (95% CI 2.0 - 4.7) for each 1 g/dL decrease in lowest Hb. In a binary recursive partitioning model for those without ACS, a lowest recorded Hb level of less than 6.3 g/dL was significantly associated with transfusion during admission (p < 0.01). Hydroxyurea use was not associated with transfusions in any analysis.Conclusion: ACS increased the RR of transfusion in children hospitalized for VOC sevenfold. In children without ACS, transfusion was associated with lowest Hb concentration, particularly Hb concentration of less than 6.3 g/dL. [ABSTRACT FROM AUTHOR]

Objectives To identify barriers to hydroxyurea adherence (negative beliefs, access, and/or recall barriers), and their relationship to adherence rates and health-related quality of life ( HRQOL) among adolescents and young adults ( AYA) with sickle cell disease ( SCD). Methods A cross-sectional survey was administered to 34 AYAs (12-22 years old) in SCD clinics from January to December 2015. Study measures included Brief Medication Questionnaire, Modified Morisky Adherence Scale 8-items, visual analog scale, and Patient Reported Outcomes Measurement Information System. Results Participants (59% male; 91% Black) had a median age of 13.5 years ( IQR 12-18). Participants reported negative beliefs (32%), recall barriers (44%), and access barriers (32%). Participants with recall barriers reported worse pain ( P=.02), fatigue ( P=.05), and depression ( P=.05). The number of adherence barriers inversely correlated with adherence level using © MMAS-8 ( rs=−.38, P=.02) and VASdose ( rs=−.25, P=.14) as well as MCV ( rs=−.45, P=.01) and HbF% ( rs=−.36, P=.05), suggesting higher hydroxyurea adherence in patients with fewer barriers. Conclusions Patients with fewer barriers to hydroxyurea adherence were more likely to have higher adherence rates and better HRQOL scores. Routine assessment of hydroxyurea adherence and its related barriers could provide actionable information to improve adherence rates, HRQOL, and other clinical outcomes. [ABSTRACT FROM AUTHOR]

In children, levels of play, physical activity, and fitness are key indicators of health and disease and closely tied to optimal growth and development. Cardiopulmonary exercise testing (CPET) provides clinicians with biomarkers of disease and effectiveness of therapy, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response that is hidden when the child is at rest. Yet the growth of clinical trials utilizing CPET in pediatrics remains stunted despite the current emphasis on preventative medicine and the growing recognition that therapies used in children should be clinically tested in children. There exists a translational gap between basic discovery and clinical application in this essential component of child health. To address this gap, the NIH provided funding through the Clinical and Translational Science Award (CTSA) program to convene a panel of experts. This report summarizes our major findings and outlines next steps necessary to enhance child health exercise medicine translational research. We present specific plans to bolster data interoperability, improve child health CPET reference values, stimulate formal training in exercise medicine for child health care professionals, and outline innovative approaches through which exercise medicine can become more accessible and advance therapeutics across the broad spectrum of child health. [ABSTRACT FROM AUTHOR]