ABSTRACT:Hydroxyurea provides effective disease-modifying treatment for people with sickle cell anemia (SCA), especially when escalated to maximum tolerated dose (MTD), which has wide interpatient dosing variability due to pharmacokinetic (PK) differences. Whether hydroxyurea PK parameters differ among children with SCA in different global regions is unknown. We compared hydroxyurea PK parameters among children with SCA from 5 clinical trials: HUSTLE (United States), TREAT (United States), NOHARM (Uganda), REACH (Uganda and Kenya), and EXTEND (Jamaica). Key hydroxyurea PK parameters were determined using HdxSim, a validated hydroxyurea PK software program. The results were compared across regions by analysis of variance. PK profiles from 451 children with SCA (146 from the United States, 265 from Africa, and 40 from the Caribbean) were included. Children from Africa had slightly lower volumes of distribution, but absorption rate and clearance were similar across regions. The PK-recommended doses to achieve MTD were statistically different but clinically similar across the United States (26.6 ± 5.9 mg/kg per day), Africa (27.6 ± 6.5 mg/kg per day), and the Caribbean (25.2 ± 4.7 mg/kg per day) (P = .04). In multivariable regression, younger age and increased reticulocyte counts were associated with higher PK-recommended doses. Hydroxyurea PK parameters in children with SCA differ minimally across global populations, predicting clinically similar doses to achieve MTD. Individualized hydroxyurea dosing based on a PK-population model derived from US children with SCA can be used broadly to maximize the benefits of this critical medication in other global populations. These trials were registered at www.ClinicalTrials.gov as #NCT00305175 (HUSTLE), #NCT02286154 (TREAT), #NCT01976416 (NOHARM), #NCT01966731 (REACH), and #NCT02556099 (EXTEND).

Abstract Children with sickle cell anemia (SCA) have poor growth and pubertal development. REACH (Realizing Effectiveness Across Continents with Hydroxyurea) is a prospective trial evaluating the feasibility, safety, and benefits of hydroxyurea at maximum tolerated dose (MTD) for children with SCA in sub-Saharan Africa. Children aged 1 to 10 years received open-label hydroxyurea with longitudinal follow-up. Height, weight, and pubertal staging were collected over 7 years of treatment. Biomarkers included insulin-like growth factor I (IGF-I), IGF-binding protein 3, luteinizing hormone, follicle-stimulating hormone, and anti-Mullerian hormone (AMH). Hydroxyurea commenced at an average (mean ± 1 standard deviation [SD]) age of 5.9 ± 2.4 years (range, 1.6-10.2) for girls (n = 296) and 5.4 ± 2.4 years (range, 1.3-10.1) for boys (n = 310). Using natural history SCA-specific reference curves, the mean weight-for-age z score improved from 0.47 ± 0.90 at enrollment to 0.69 ± 1.00 on hydroxyurea treatment. Height increased from 0.26 ± 0.90 to 0.42 ± 1.00 on treatment, and body mass index from 0.46 ± 1.00 to 0.85 ± 1.20. IGF-I remained low in many participants. Puberty was delayed in 25% to 30% of children, with gradual progress on treatment. AMH was low (<2.5th percentile) in 4% of girls, whereas 52% of boys had low AMH at baseline and 28% at follow-up. Long-term hydroxyurea treatment at MTD is associated with beneficial effects on growth with improved weight and height, and does not negatively affect pubertal developmenty in children with SCA in sub-Saharan Africa. This study was registered at www.clinicaltrials.gov initially as NCT01966731 and is now registered as NCT06171217 for long-term follow-up.

Abstract Sickle cell anemia (SCA) is a life-threatening hemoglobinopathy with worldwide distribution. Featuring multiple acute and chronic complications, SCA is also associated with growth impairment. A lack of appropriate reference data on height, weight, and body mass index (BMI) impedes assessment of the effect of therapies on growth in African children with SCA. The World Health Organization (WHO) growth curves are derived from healthy populations. We analyzed 6095 height and weight paired measurements (2875 in females, 3220 in males; median, 5 measurements/child) from 864 children with SCA, aged 6 months to 19 years, in Kilifi, Kenya. The growth percentile trajectories showed substantial delays when compared with the WHO curves. The female deficits in median height were 7 cm at age 5 years, 11 cm at 10 years, and 13 cm at age 15 years. Male height deficits were 6 cm at 5 years, 10 cm at 10 years, and 21 cm at 15 years. Median weight deficits were 3.4 kg at 5 years and 9.1 kg at 10 years for females, and 3.0 kg at 5 years and 7.7 kg at 10 years for males. The median BMI was lower by 5 kg/m2 at 15 years for both females and males. These newly developed Kilifi SCA growth curves provide useful disease-specific references for clinicians and researchers.

Children with sickle cell anemia (SCA) in Africa frequently require transfusions for SCA complications. Despite limited blood supplies, strategies to reduce their transfusion needs have not been widely evaluated or implemented. We analyzed transfusion utilization in children with SCA before and during hydroxyurea treatment. REACH (Realizing Effectiveness Across Continents with Hydroxyurea, NCT01966731) is a longitudinal Phase I/II trial of hydroxyurea in children with SCA from Angola, Democratic Republic of Congo, Kenya, and Uganda. After enrollment, children had a two-month pre-treatment screening period followed by 6 months of fixed-dose hydroxyurea (15-20 mg/kg/day), 18 months of dose escalation, and then stable dosing at maximum tolerated dose (MTD). Characteristics associated with transfusions were analyzed with univariate and multivariable models. Transfusion incidence rate ratios (IRR) across treatment periods were calculated. Among 635 enrolled children with 4124 person-years of observation, 258 participants (40.4%) received 545 transfusions. The transfusion rate per 100 person-years was 43.2 before hydroxyurea, 21.7 on fixed-dose, 14.5 during dose escalation, and 10.8 on MTD. During MTD, transfusion incidence was reduced by 75% compared to pre-treatment (IRR 0.25, 95% confidence interval [CI] 0.18-0.35, p < .0001), and by 50% compared to fixed dose (IRR 0.50, 95% CI 0.39-0.63, p < .0001). Hydroxyurea at MTD decreases transfusion utilization in African children with SCA. If widely implemented, universal testing and hydroxyurea treatment at MTD could potentially prevent 21% of all pediatric transfusions administered in sub-Saharan Africa. Increasing hydroxyurea access for SCA should decrease the transfusion burden and increase the overall blood supply.

Background: The Kilifi Health and Demographic Surveillance System (KHDSS) was established in 2000 to define the incidence and prevalence of local diseases and evaluate the impact of community-based interventions. KHDSS morbidity data have been reported comprehensively but mortality has not been described. This analysis describes mortality in the KHDSS over 16 years. Methods: We calculated mortality rates from 2003–2018 in four intervals of equal duration and assessed differences in mortality across these intervals by age and sex. We calculated the period survival function and median survival using the Kaplan–Meier method and mean life expectancies using abridged life tables. We estimated trend and seasonality by decomposing a time series of monthly mortality rates. We used choropleth maps and random-effects Poisson regression to investigate geographical heterogeneity. Results: Mortality declined by 36% overall between 2003–2018 and by 59% in children aged <5 years. Most of the decline occurred between 2003 and 2006. Among adults, the greatest decline (49%) was observed in those aged 15–54 years. Life expectancy at birth increased by 12 years. Females outlived males by 6 years. Seasonality was only evident in the 1–4 year age group in the first four years. Geographical variation in mortality was ±10% of the median value and did not change over time. Conclusions: Between 2003 and 2018, mortality among children and young adults has improved substantially. The steep decline in 2003–2006 followed by a much slower reduction thereafter suggests improvements in health and wellbeing have plateaued in the last 12 years. However, there is substantial inequality in mortality experience by geographical location.

ABSTRACTBackgroundThe impact of COVID-19 on all-cause mortality in sub-Saharan Africa remains unknown.MethodsWe monitored mortality among 306,000 residents of Kilifi Health and Demographic Surveillance System, Kenya, through four COVID-19 waves from April 2020-September 2021. We calculated expected deaths using negative binomial regression fitted to baseline mortality data (2010-2019) and calculated excess mortality as observed-minus-expected deaths. We excluded deaths in infancy because of under-ascertainment of births during lockdown. In February 2021, after two waves of wild-type COVID-19, adult seroprevalence of anti-SARS-CoV-2 was 25.1%. We predicted COVID-19-attributable deaths as the product of age-specific seroprevalence, population size and global infection fatality ratios (IFR). We examined changes in cause of death by Verbal Autopsy (VA).ResultsBetween April 2020 and February 2021, we observed 1,000 deaths against 1,012 expected deaths (excess mortality -1.2%, 95% PI -6.6%, 5.8%). Based on SARS-CoV-2 seroprevalence, we predicted 306 COVID-19-attributable deaths (a predicted excess mortality of 30.6%) within this period. Monthly mortality analyses showed a significant excess among adults aged ≥45 years in only two months, July-August 2021, coinciding with the fourth (Delta) wave of COVID-19. By September 2021, overall excess mortality was 3.2% (95% PI -0.6%, 8.1%) and cumulative excess mortality risk was 18.7/100,000. By VA, there was a transient reduction in deaths attributable to acute respiratory infections in 2020.ConclusionsNormal mortality rates during extensive transmission of wild-type SARS-CoV-2 through February 2021 suggests that the IFR for this variant is lower in Kenya than elsewhere. We found excess mortality associated with the Delta variant but the cumulative excess mortality risk remains low in coastal Kenya compared to global estimates.

Background: In sickle cell anaemia (SCA), the spleen is one of the first organs to be damaged. The unique environment of the spleen particularly challenges red blood cell (RBC) deformability, causing constant intrasplenic sickling and recurrent splenic ischaemia from early childhood. It is well-established that splenic function is lost within the first years of life in most children with SCA. Spleen size, however, varies significantly and the determinants of phenotypical variations are not fully understood. Multiple genetic and external factors may contribute to spleen size in SCA. High levels of haemoglobin F (HbF) and co-inheritance of α-thalassaemia have been associated with persistent splenomegaly, as has the presence of irreversibly sickled cells. In this study we assessed the relationship between RBC deformability, spleen size and splenic filtration function in children with SCA. Methods: We recruited children aged 0 to 16 years with a confirmed diagnosis of SCA (HbSS) from the paediatric haematology clinic at King's College Hospital in London between December 2018 and January 2019. Children were excluded from the study if they had previously undergone surgical splenectomy or if they had received any blood transfusions within three months of study recruitment. If children were receiving hydroxycarbamide treatment at the time of recruitment, therapy for less than three months also warranted study exclusion. Measurements of spleen size were obtained for all children using abdominal ultrasound. All ultrasound examinations were performed in clinic by a single examiner to ensure comparability of results. Splenic function was assessed by manual pitted RBC counts. RBCs were fixed in 2% PBS-buffered paraformaldehyde on the day of venepuncture and differential interference contrast (DIC) microscopy was performed within three months of sampling. A minimum of 500 consecutive RBCs were counted for each sample and the proportion of cells with one or more pits was expressed as a percentage of the total number of counted cells (%PIT). RBC deformability was measured using the Oxygenscan module of the Laser Optical Rotational Red Cell Analyser (Lorrca, RR Mechatronics, Zwaag, The Netherlands). Samples for deformability analyses were stored at 4°C and analysed between 24 and 48h from sampling. Results: A total of 91 children were included in the study. Ages ranged from 7 months to 16 years, with a mean age of 8.4 years. Of the 91 children, 43 (47.3%) were treated with hydroxycarbamide. Data on α-thalassaemia genotype were available for 88 children: 7 were homozygous for the 3.7 kb deletion, 33 were heterozygous for the 3.7 kb deletion and 47 had no detected deletions. RBC deformability expressed as the elongation index (EI) at normal oxygen tensions (EImax) and after deoxygenation (EImin) was found to correlate positively with spleen length (EImax: r = 0.41, P < 0.001; EImin: r = 0.36, P < 0.001), and the point of sickling (POS) to correlate negatively with spleen length (r = -0.36, P < 0.001). Results for EImax, EImin and POS remained significant when adjusting for %HbF and α-thalassaemia genotype in multiple linear regression models (EImax: P < 0.001; EImin: P = 0.005; POS: P = 0.003). EImax and EImin both correlated negatively with %PIT (EImax: r = -0.60, P < 0.001; EImin: r = -0.34, P < 0.001) and POS correlated positively with %PIT (r = 0.50, P <0.001). Results for EImax, EImin and POS remained significant when adjusting for %HbF in multiple linear regression models (EImax: P < 0.001; EImin: P = 0.03; POS: P < 0.001). Conclusions: We assessed the association between RBC deformability measured using oxygen gradient ektacytometry, spleen size and splenic filtration in 91 children with SCA. Results suggested that children with larger spleens had improved RBC deformability, expressed as a higher EImax and EImin, and increased RBC tolerance to deoxygenation, expressed as a lower POS. Results also suggested that improved deformability and increased RBC tolerance to deoxygenation was associated with improved splenic filtration, expressed as a lower %PIT. Although it is difficult to interpret the causal relationship between RBC deformability and splenic injury, our results indicate that decreased deformability contributes to loss of splenic filtration as well as phenotypical variations in spleen size in children with SCA. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The loss of red blood cell (RBC) deformability in sickle cell anaemia (SCA) is considered the primary factor responsible for episodes of acute pain and downstream progressive organ dysfunction. Oxygen gradient ektacytometry (Oxygenscan) is a recently commercialised functional assay that aims to describe the deformability of RBCs in SCA at differing oxygen tensions. So far, the Oxygenscan has been evaluated only by a small number of research groups and the validity and clinical value of Oxygenscan-derived biomarkers have not yet been fully established. In this study we examined RBC deformability measured with the Oxygenscan in 91 children with SCA at King's College Hospital in London. We found a significant correlation between Oxygenscan-derived biomarkers and well-recognised modifiers of disease severity in SCA: haemoglobin F and co-inherited α-thalassaemia. We failed, however, to find any independent predictive value of the Oxygenscan in the clinical outcome measure of pain, as well as other important parameters such as hydroxycarbamide treatment. Although the Oxygenscan remains an intriguing tool for basic research, our results question whether it provides any additional information in predicting the clinical course in children with SCA, beyond measuring known markers of disease severity.

We present a feasibility study on the use of a time domain NIRS instrument, named MAESTROS, to explore the cerebral optical parameters and physiology of people with multiple sclerosis.

Background: The -α3.7I-thalassaemia deletion is very common throughout Africa because it protects against malaria. When undertaking studies to investigate human genetic adaptations to malaria or other diseases, it is important to account for any confounding effects of α-thalassaemia to rule out spurious associations. Methods: In this study, we have used direct α-thalassaemia genotyping to understand why GWAS data from a large malaria association study in Kilifi Kenya did not identify the α-thalassaemia signal. We then explored the potential use of a number of new approaches to using GWAS data for imputing α-thalassaemia as an alternative to direct genotyping by PCR. Results: We found very low linkage-disequilibrium of the directly typed data with the GWAS SNP markers around α-thalassaemia and across the haemoglobin-alpha (HBA) gene region, which along with a complex haplotype structure, could explain the lack of an association signal from the GWAS SNP data. Some indirect typing methods gave results that were in broad agreement with those derived from direct genotyping and could identify an association signal, but none were sufficiently accurate to allow correct interpretation compared with direct typing, leading to confusing or erroneous results. Conclusions: We conclude that going forwards, direct typing methods such as PCR will still be required to account for α-thalassaemia in GWAS studies.

Background: The -α3.7I-thalassaemia deletion is very common throughout Africa because it protects against malaria. When undertaking studies to investigate human genetic adaptations to malaria or other diseases, it is important to account for any confounding effects of α-thalassaemia to rule out spurious associations. Methods: In this study, we have used direct α-thalassaemia genotyping to understand why GWAS data from a large malaria association study in Kilifi Kenya did not identify the α-thalassaemia signal. We then explored the potential use of a number of new approaches to using GWAS data for imputing α-thalassaemia as an alternative to direct genotyping by PCR. Results: We found very low linkage-disequilibrium of the directly typed data with the GWAS SNP markers around α-thalassaemia and across the haemoglobin-alpha (HBA) gene region, which along with a complex haplotype structure, could explain the lack of an association signal from the GWAS SNP data. Some indirect typing methods gave results that were in broad agreement with those derived from direct genotyping and could identify an association signal, but none were sufficiently accurate to allow correct interpretation compared with direct typing, leading to confusing or erroneous results. Conclusions: We conclude that going forwards, direct typing methods such as PCR will still be required to account for α-thalassaemia in GWAS studies.