Hydroxyurea treatment is associated with lower malaria incidence in children with sickle cell anemia in sub-Saharan Africa.

Realizing Effectiveness Across Continents with Hydroxyurea (REACH, NCT01966731) provides hydroxyurea at maximum tolerated dose (MTD) for children with sickle cell anemia (SCA) in sub-Saharan Africa. Beyond reducing SCA-related clinical events, documented treatment benefits include ∼50% reduction in malaria incidence. To identify associations and propose mechanisms by which hydroxyurea could be associated with lower malaria rates, infections were recorded across all clinical sites (Angola, Democratic Republic of Congo, Kenya, and Uganda). Hazard ratios (HR) with 95% confidence intervals (CIs) for baseline demographics, and time-varying laboratory and clinical parameters were estimated in a modified Cox gap-time model for repeated events. Over 3387 patient-years of hydroxyurea treatment, 717 clinical malaria episodes occurred in 336 of 606 study participants; over half were confirmed by blood smear and/or rapid diagnostic testing with 97.8% Plasmodium falciparum. In univariate analysis limited to 4 confirmed infections per child, malaria risk was significantly associated with absolute neutrophil count (ANC), splenomegaly, hemoglobin, and achieving MTD; age, malaria season, MTD dose, fetal hemoglobin, α-thalassemia, and glucose-6-phosphate dehydrogenase deficiency had no effect. In multivariable regression of confirmed infections, ANC was significant (HR, 1.37 per doubled value; 95% CI, 1.10-1.70; P = .0052), and ANC values <3.0 × 109/L were associated with lower malaria incidence. Compared with nonpalpable spleen, 1- to 4-cm splenomegaly also was associated with higher malaria risk (HR, 2.01; 95% CI, 1.41-2.85; P = .0001). Hydroxyurea at MTD is associated with lower malaria incidence in SCA through incompletely defined mechanisms, but treatment-associated mild myelosuppression with ANC <3.0 × 109/L is salutary. Splenomegaly is an unexplained risk factor for malaria infections among children with SCA in Africa.

Stroke Prevention with Hydroxyurea Enabled through Research and Education: A Phase 2 Primary Stroke Prevention Trial in Sub-Saharan Africa.

INTRODUCTION: Stroke is a severe complication of sickle cell anemia (SCA), with devastating sequelae. Transcranial Doppler (TCD) ultrasonography predicts stroke risk, but implementing TCD screening with suitable treatment for primary stroke prevention in low-resource environments remains challenging. SPHERE (NCT03948867) is a prospective phase 2 open-label hydroxyurea trial for SCA in Tanzania. METHODS: After formal training and certification, local personnel screened children 2-16 years old; those with conditional (170-199 cm/s) or abnormal (≥200 cm/s) time-averaged mean velocities (TAMVs) received hydroxyurea at 20 mg/kg/day with dose escalation to maximum tolerated dose (MTD). The primary study endpoint is change in TAMV after 12 months of hydroxyurea; secondary endpoints include SCA-related clinical events, splenic volume and function, renal function, infections, hydroxyurea pharmacokinetics, and genetic modifiers. RESULTS: Between April 2019 and April 2020, 202 children (average 6.8 ± 3.5 years, 53% female) enrolled and underwent TCD screening; 196 were deemed eligible by DNA testing. Most had numerous previous hospitalizations and transfusions, with low baseline hemoglobin (7.7 ± 1.1 g/dL) and %HbF (9.3 ± 5.4%). Palpable splenomegaly was present at enrollment in 49 (25%); average sonographic splenic volume was 103 mL (range 8-1,045 mL). TCD screening identified 22% conditional and 2% abnormal velocities, with hydroxyurea treatment initiated in 96% (45/47) eligible children. CONCLUSION: SPHERE has built local capacity with high-quality research infrastructure and TCD screening for SCA in Tanzania. Fully enrolled participants have a high prevalence of elevated baseline TCD velocities and splenomegaly. SPHERE will prospectively determine the benefits of hydroxyurea at MTD for primary stroke prevention, anticipating expanded access to hydroxyurea treatment across Tanzania.

Operational analysis of the national sickle cell screening programme in the Republic of Uganda.

BACKGROUND: Sickle cell anaemia is a common global life-threatening haematological disorder. Most affected births occur in sub-Saharan Africa where children usually go undiagnosed and die early in life. Uganda's national sickle cell screening programme was developed in response to a 2014 sickle cell surveillance study that documented a high disease prevalence. OBJECTIVE: This study describes the temporal and financial aspects of Uganda's 2014-2019 sickle cell screening programme. METHODS: National sickle cell screening data from Uganda's Central Public Health Laboratories were used to calculate turn-around times (TATs) from sample collection to delivery, testing, and result reporting for blood samples collected from February 2014 to March 2019. The parameters affecting specific TATs were assessed. The exact programme expenditures were analysed to determine cost per test and per positive sickle cell disease case detected. RESULTS: A total of 278 651 samples were analysed. The median TAT from sample collection to laboratory receipt was 8 days (interquartile range [IQR]: 6-12), receipt to testing was 3 days (IQR: 1-7), and testing to result reporting was 6 days (IQR: 3-12). Altogether, the sample continuum averaged 16 days (IQR: 11-24). Lower level healthcare facilities were associated with longer sample delivery TATs. Calendar months (January and December) and larger sample volumes impacted testing and result reporting TATs. The cost per test was $4.46 (United States dollars [USD]) and $483.74 USD per positive case detected. CONCLUSION: Uganda's sickle cell screening programme is efficient and cost-effective. Universal newborn screening is the best strategy for detecting sickle cell anaemia in Uganda.

Trends in sickle cell trait and disease screening in the Republic of Uganda, 2014-2019.

OBJECTIVE: Sickle cell disease is an important public health issue that is increasingly recognised as a substantial contributor to morbidity and early childhood mortality in sub-Saharan Africa. We aimed to provide information from large-scale, long-term sickle cell screening efforts in Africa. METHODS: We used nationally representative data from the centralised public health laboratory database in Uganda to examine epidemiological trends in sickle cell screening over a five-year period, comparing age and geographic adjustments to prevalence among different testing cohorts of children aged 0-24 months, and calculating screening coverage within high-burden districts. RESULTS: A total of 324 356 children aged 0-24 months were screened for sickle cell trait and disease from February 2014 to March 2019. A high national burden of sickle cell disease (0.9%) was confirmed among a cohort of samples co-tested with HIV. In the cohort of samples referred specifically for sickle cell testing, the overall prevalence of sickle cell disease was 9.7% and particularly elevated in high-burden districts where focused screening occurred. The majority of children were screened before age 4 months, but the sickle-specific cohort had a larger proportion of affected children tested between age 5-9 months, coincident with onset of disease signs and symptoms. Successful screening coverage of sickle cell disease births was achieved in several high-burden districts. CONCLUSIONS: Examination and analysis of national sickle cell screening trends in Uganda documents the successes of focused screening strategies as an important step towards universal screening. With this evidence and increased healthcare provider knowledge, Uganda can optimise sickle cell diagnosis and management across the country.

OBJECTIF: La drépanocytose est un problème important de santé publique, de plus en plus reconnu comme un contributeur important à la morbidité et à la mortalité infantile en Afrique subsaharienne. Notre objectif était de fournir des informations sur les efforts de dépistage de la drépanocytose à grande échelle et à long terme en Afrique. MÉTHODES: Nous avons utilisé des données représentatives nationales de la base de données centralisée des laboratoires de santé publique en Ouganda pour examiner les tendances épidémiologiques dans le dépistage de la drépanocytose sur une période de cinq ans, en comparant l'âge et les ajustements géographiques à la prévalence dans différentes cohortes de tests d'enfants âgés de 0 à 24 mois, et en estimant la couverture du dépistage dans les districts à forte charge. RÉSULTATS: Un total de 324.356 enfants âgés de 0 à 24 mois ont été dépistés pour le trait drépanocytaire et la maladie de février 2014 à mars 2019. Une charge nationale élevée de la drépanocytose (0,9%) a été confirmée dans une cohorte d'échantillons co-testés pour le VIH. Dans la cohorte d'échantillons référés spécifiquement pour le dépistage de la drépanocytose, la prévalence globale de la drépanocytose était de 9,7% et particulièrement élevée dans les districts à forte charge où un dépistage ciblé avait eu lieu. La majorité des enfants ont été dépistés avant l'âge de 4 mois, mais la cohorte spécifique pour la drépanocytose avait une plus grande proportion d'enfants affectés testés entre l'âge de 5 à 9 mois, coïncidant avec l'apparition des signes et symptômes de la maladie. Une bonne couverture de dépistage des naissances drépanocytaires a été obtenue dans plusieurs districts à forte charge. CONCLUSIONS: L'examen et l'analyse des tendances nationales du dépistage de la drépanocytose en Ouganda documentent les succès des stratégies de dépistage ciblé comme une étape importante vers le dépistage universel. Grâce à ces données et à une meilleure connaissance des prestataires de soins de santé, l'Ouganda peut optimiser le diagnostic et la prise en charge de la drépanocytose dans tout le pays.

Hydroxyurea Pharmacokinetics in Pediatric Patients After Total Pancreatectomy With Islet Autotransplantation.

Total pancreatectomy with islet autotransplantation is a complex surgical approach for acute recurrent or chronic pancreatitis that frequently triggers extreme thrombocytosis (platelets ≥ 1000 × 109 /L). Thrombocytosis can be prothrombotic, so cytoreductive hydroxyurea is often initiated after this surgery; however, optimal dosing strategy and efficacy are unknown. This prospective pilot study characterized the pharmacokinetics of hydroxyurea after this procedure in children. It also compared them with previously published pediatric parameters in sickle cell anemia (SCA), the disease in which pediatric hydroxyurea pharmacokinetics have primarily been studied. Plasma hydroxyurea levels were quantified in 14 participants aged 4-19 years using high-performance liquid chromatography. Blood collections were scheduled 20 minutes, 1 hour, and 4 hours after the first dose, on pharmacokinetic day 1 (PK1), and again 2-3 months later if still on hydroxyurea (PK2). Six participants had PK1 and PK2 data at all 3 postdose timed collections, 5 only had PK1 samples, and 3 only had PK2 samples. Total pancreatectomy with islet autotransplantation participants had reduced and delayed absorption compared with sickle cell anemia participant data from the Hydroxyurea Study of Long-Term Effects, regardless of timing or dosing methodology. Total pancreatectomy with islet autotransplantation participants had different pharmacokinetic profiles at PK1 versus PK2, with lower dose-normalized exposures than previously reported in sickle cell anemia. These results suggest variability exists in hydroxyurea absorption and bioavailability in total pancreatectomy with islet autotransplantation patients, suspected to be primarily because of Roux-en-Y reconstruction, and suggest that more pharmacokinetic data are needed for scenarios when hydroxyurea is prescribed to children without sickle cell anemia.

Operational analysis of the national sickle cell screening programme in the Republic of Uganda

Background: Sickle cell anaemia is a common global life-threatening haematological disorder. Most affected births occur in sub-Saharan Africa where children usually go undiagnosed and die early in life. Uganda's national sickle cell screening programme was developed in response to a 2014 sickle cell surveillance study that documented a high disease prevalence. Objective: This study describes the temporal and financial aspects of Uganda's 2014­2019 sickle cell screening programme. Methods: National sickle cell screening data from Uganda's Central Public Health Laboratories were used to calculate turn-around times (TATs) from sample collection to delivery, testing, and result reporting for blood samples collected from February 2014 to March 2019. The parameters affecting specific TATs were assessed. The exact programme expenditures were analysed to determine cost per test and per positive sickle cell disease case detected. Results: A total of 278 651 samples were analysed. The median TAT from sample collection to laboratory receipt was 8 days (interquartile range [IQR]: 6­12), receipt to testing was 3 days (IQR: 1­7), and testing to result reporting was 6 days (IQR: 3­12). Altogether, the sample continuum averaged 16 days (IQR: 11­24). Lower level healthcare facilities were associated with longer sample delivery TATs. Calendar months (January and December) and larger sample volumes impacted testing and result reporting TATs. The cost per test was $4.46 (United States dollars [USD]) and $483.74 USD per positive case detected. Conclusion: Uganda's sickle cell screening programme is efficient and cost-effective. Universal newborn screening is the best strategy for detecting sickle cell anaemia in Uganda.

Surveillance for sickle cell disease, United Republic of Tanzania.

OBJECTIVE: To determine the regional- and district-level newborn prevalence of sickle cell trait and disease, and the prevalence of haemoglobin variants and genetic modifiers of sickle cell disease, in the nine regions of north-western United Republic of Tanzania. METHODS: We repurposed dried blood spot samples from children (aged 0-24 months) born to mothers living with human immunodeficiency virus (HIV), collected as part of the HIV Early Infant Diagnosis programme, for sickle cell diagnosis. We performed isoelectric focusing to determine whether samples had normal haemoglobin, sickle cell trait, sickle cell disease or a rare haemoglobin variant. We shipped samples diagnosed as disease or variant to Cincinnati Children's Hospital in the United States of America for deoxyribonucleic-acid-based analyses to determine the prevalence of α-thalassaemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency or fetal haemoglobin genetic modifiers. FINDINGS: We analysed a total of 17 200 specimens during February 2017-May 2018. We observed a prevalence of sickle cell trait and disease of 20.3% (3492/17 200) and 1.2% (210/17 200), respectively. District-level trait varied from 8.6% (5/58) to 28.1% (77/274). Among confirmed sickle cell disease specimens, we noted 42.7% (61/143) had 1-gene deletion and 14.7% (21/143) had 2-gene deletion α-thalassaemia trait. We documented G6PD A- deficiency in 19.2% (14/73) of males. CONCLUSION: Our calculated prevalence is twice as high as previously reported and reinforces the need for enhanced sickle cell diagnostic services. Our district-level data will inform public health policy, allowing screening and disease-modifying hydroxyurea therapy to be focused on high-prevalence areas, until universal newborn screening is available.

AnemoCheck-LRS: an optimized, color-based point-of-care test to identify severe anemia in limited-resource settings.

BACKGROUND: Severe anemia is common and frequently fatal for hospitalized patients in limited-resource settings. Lack of access to low-cost, accurate, and rapid diagnosis of anemia impedes the delivery of life-saving care and appropriate use of the limited blood supply. The WHO Haemoglobin Colour Scale (HCS) is a simple low-cost test but frequently inaccurate. AnemoCheck-LRS (limited-resource settings) is a rapid, inexpensive, color-based point-of-care (POC) test optimized to diagnose severe anemia. METHODS: Deidentified whole blood samples were diluted with plasma to create variable hemoglobin (Hb) concentrations, with most in the severe (≤ 7 g/dL) or profound (≤ 5 g/dL) anemia range. Each sample was tested with AnemoCheck-LRS and WHO HCS independently by three readers and compared to Hb measured by an electronic POC test (HemoCue 201+) and commercial hematology analyzer. RESULTS: For 570 evaluations within the limits of detection of AnemoCheck-LRS (Hb ≤ 8 g/dL), the average difference between AnemoCheck-LRS and measured Hb was 0.5 ± 0.4 g/dL. In contrast, the WHO HCS overestimated Hb with an absolute difference of 4.9 ± 1.3 g/dL for samples within its detection range (Hb 4-14 g/dL, n = 405). AnemoCheck-LRS was much more sensitive (92%) for the diagnosis of profound anemia than WHO HCS (22%). CONCLUSIONS: AnemoCheck-LRS is a rapid, inexpensive, and accurate POC test for anemia. AnemoCheck-LRS is more accurate than WHO HCS for detection of low Hb levels, severe anemia that may require blood transfusion. AnemoCheck-LRS should be tested prospectively in limited-resource settings where severe anemia is common, to determine its utility as a screening tool to identify patients who may require transfusion.

Sickle cell screening in Uganda: High burden, human immunodeficiency virus comorbidity, and genetic modifiers.

BACKGROUND: The Uganda Sickle Surveillance Study provided evidence for a large sickle burden among HIV-exposed infants in Uganda. To date, however, no large scale screening program has been developed for Central or East Africa. METHODS: A 3-year targeted sickle cell screening project in Uganda was designed by the Ministry of Health to (1) determine sickle cell trait and disease prevalence within high-burden districts, (2) document the prevalence among HIV-exposed and nonexposed children, (3) confirm previously suggested HIV comorbidity, and (4) estimate the co-inheritance of known genetic modifiers of sickle cell disease. RESULTS: A total of 163 334 dried blood spot samples collected between April 2015 and March 2018 were analyzed, including 112 352 samples within the HIV Early Infant Diagnosis program. A high burden with >1% sickle cell disease was found within targeted East Central and Mid-Northern districts, in both HIV-exposed and nonexposed children. Based on crude birth-rate data, 236 905 sickle cell trait births and 16 695 sickle cell disease births will occur annually in Uganda. Compared to sickle cell disease without HIV, the odds ratio of having sickle cell disease plus HIV was 0.50 (95% confidence interval = 0.40-0.64, P < .0001). Alpha-thalassemia trait and G6PD deficiency were common with sickle cell disease, but with different geospatial distribution. CONCLUSIONS: High sickle cell burden and potential HIV comorbidity are confirmed in Uganda. Genetic modifiers are common and likely influence laboratory and clinical phenotypes. These prospective data document that targeted sickle cell screening is feasible and effective in Uganda, and support development of district-level comprehensive care programs.

Robust clinical and laboratory response to hydroxyurea using pharmacokinetically guided dosing for young children with sickle cell anemia.

Hydroxyurea is FDA-approved and now increasingly used for children with sickle cell anemia (SCA), but dosing strategies, pharmacokinetic (PK) profiles, and treatment responses for individual patients are highly variable. Typical weight-based dosing with step-wise escalation to maximum tolerated dose (MTD) leads to predictable laboratory and clinical benefits, but often takes 6 to 12 months to achieve. The Therapeutic Response Evaluation and Adherence Trial (TREAT, NCT02286154) was a single-center study designed to prospectively validate a novel personalized PK-guided hydroxyurea dosing strategy with a primary endpoint of time to MTD. Enrolled participants received a single oral 20 mg/kg dose of hydroxyurea, followed by a sparse PK sampling approach with three samples collected over three hours. Analysis of individual PK data into a population PK model generated a starting dose that targets the MTD. The TREAT cohort (n = 50) was young, starting hydroxyurea at a median age of 11 months (IQR 9-26 months), and PK-guided starting doses were high (27.7 ± 4.9 mg/kg/d). Time to MTD was 4.8 months (IQR 3.3-9.3), significantly shorter than comparison studies (p < 0.0001), thus meeting the primary endpoint. More remarkably, the laboratory response for participants starting with a PK-guided dose was quite robust, achieving higher hemoglobin (10.1 ± 1.3 g/dL) and HbF (33.3 ± 9.1%) levels than traditional dosing. Though higher than traditional dosing, PK-guided doses were safe without excess hematologic toxicities. Our data suggest early initiation of hydroxyurea, using a personalized dosing strategy for children with SCA, provides laboratory and clinical response beyond what has been seen historically, with traditional weight-based dosing.

Prevalence of inherited blood disorders and associations with malaria and anemia in Malawian children.

In sub-Saharan Africa, inherited causes of anemia are common, but data are limited regarding the geographical prevalence and coinheritance of these conditions and their overall contributions to childhood anemia. To address these questions in Malawi, we performed a secondary analysis of the 2015-2016 Malawi Micronutrient Survey, a nationally and regionally representative survey that estimated the prevalence of micronutrient deficiencies and evaluated both inherited and noninherited determinants of anemia. Children age 6 to 59 months were sampled from 105 clusters within the 2015-2016 Malawi Demographic Health Survey. Hemoglobin, ferritin, retinol binding protein, malaria, and inflammatory biomarkers were measured from venous blood. Molecular studies were performed using dried blood spots to determine the presence of sickle cell disease or trait, α-thalassemia trait, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Of 1279 eligible children, 1071 were included in the final analysis. Anemia, iron deficiency, and malaria were common, affecting 30.9%, 21.5%, and 27.8% of the participating children, respectively. α-Thalassemia trait was common (>40% of children demonstrating deletion of 1 [33.1%] or 2 [10.0%] α-globin genes) and associated with higher prevalence of anemia (P < .001). Approximately 20% of males had G6PD deficiency, which was associated with a 1.0 g/dL protection in hemoglobin decline during malaria infection (P = .02). These data document that inherited blood disorders are common and likely play an important role in the prevalence of anemia and malaria in Malawian children.

Realizing effectiveness across continents with hydroxyurea: Enrollment and baseline characteristics of the multicenter REACH study in Sub-Saharan Africa.

Despite its well-described safety and efficacy in the treatment of sickle cell anemia (SCA) in high-income settings, hydroxyurea remains largely unavailable in sub-Saharan Africa, where more than 75% of annual SCA births occur and many comorbidities exist. Realizing Effectiveness Across Continents with Hydroxyurea (REACH, ClinicalTrials.gov NCT01966731) is a prospective, Phase I/II open-label trial of hydroxyurea designed to evaluate the feasibility, safety, and benefits of hydroxyurea treatment for children with SCA in four sub-Saharan African countries. Following comprehensive training of local research teams, REACH was approved by local Ethics Committees and achieved full enrollment ahead of projections with 635 participants enrolled over a 30-month period, despite half of families living >12 km from their clinical site. At enrollment, study participants (age 5.4 ± 2.4 years) had substantial morbidity, including a history of vaso-occlusive pain (98%), transfusion (68%), malaria (85%), and stroke (6%). Significant differences in laboratory characteristics were noted across sites, with lower hemoglobin concentrations (P < .01) in Angola (7.2 ± 1.0 g/dL) and the DRC (7.0 ± 0.9 g/dL) compared to Kenya (7.4 ± 1.1 g/dL) and Uganda (7.5 ± 1.1 g/dL). Analysis of known genetic modifiers of SCA demonstrated a high frequency of α-thalassemia (58.4% with at least a single α-globin gene deletion) and G6PD deficiency (19.7% of males and 2.4% of females) across sites. The CAR ß-globin haplotype was present in 99% of participants. The full enrollment to REACH confirms the feasibility of conducting high-quality SCA research in Africa; this study will provide vital information to guide safe and effective dosing of hydroxyurea for children with SCA living in Africa.

Genetic Modifiers of White Blood Cell Count, Albuminuria and Glomerular Filtration Rate in Children with Sickle Cell Anemia.

Discovery and validation of genetic variants that influence disease severity in children with sickle cell anemia (SCA) could lead to early identification of high-risk patients, better screening strategies, and intervention with targeted and preventive therapy. We hypothesized that newly identified genetic risk factors for the general African American population could also impact laboratory biomarkers known to contribute to the clinical disease expression of SCA, including variants influencing the white blood cell count and the development of albuminuria and abnormal glomerular filtration rate. We first investigated candidate genetic polymorphisms in well-characterized SCA pediatric cohorts from three prospective NHLBI-supported clinical trials: HUSTLE, SWiTCH, and TWiTCH. We also performed whole exome sequencing to identify novel genetic variants, using both a discovery and a validation cohort. Among candidate genes, DARC rs2814778 polymorphism regulating Duffy antigen expression had a clear influence with significantly increased WBC and neutrophil counts, but did not affect the maximum tolerated dose of hydroxyurea therapy. The APOL1 G1 polymorphism, an identified risk factor for non-diabetic renal disease, was associated with albuminuria. Whole exome sequencing discovered several novel variants that maintained significance in the validation cohorts, including ZFHX4 polymorphisms affecting both the leukocyte and neutrophil counts, as well as AGGF1, CYP4B1, CUBN, TOR2A, PKD1L2, and CD163 variants affecting the glomerular filtration rate. The identification of robust, reliable, and reproducible genetic markers for disease severity in SCA remains elusive, but new genetic variants provide avenues for further validation and investigation.

Burden of sickle cell trait and disease in the Uganda Sickle Surveillance Study (US3): a cross-sectional study.

BACKGROUND: Sickle cell disease contributes substantially to mortality in children younger than 5 years in sub-Saharan Africa. In Uganda, 20,000 babies per year are thought to be born with sickle cell disease, but accurate data are not available. We did the cross-sectional Uganda Sickle Surveillance Study to assess the burden of disease. METHODS: The primary objective of the study was to calculate prevalence of sickle cell trait and disease. We obtained punch samples from dried blood spots routinely collected from HIV-exposed infants in ten regions and 112 districts across Uganda for the national Early Infant Diagnosis programme. Haemoglobin electrophoresis by isoelectric focusing was done on all samples to identify those from babies with sickle trait or disease. FINDINGS: Between February, 2014, and March, 2015, 99,243 dried blood spots were analysed and results were available for 97,631. The overall number of children with sickle cell trait was 12,979 (13·3%) and with disease was 716 (0·7%). Sickle cell numbers ranged from 631 (4·6%) for trait and 23 (0·2%) for disease of 13,649 in the South Western region to 1306 (19·8%) for trait and 96 (1·5%) for disease of 6581 in the East Central region. Sickle cell trait was seen in all districts. The lowest prevalence was less than 3·0% in two districts. Eight districts had prevalence greater than 20·0%, with the highest being 23·9%. Sickle cell disease was less common in children older than 12 months or who were HIV positive, which is consistent with comorbidity and early mortality. INTERPRETATION: Prevalence of sickle cell trait and disease were high in Uganda, with notable variation between regions and districts. The data will help to inform national strategies for sickle cell disease, including neonatal screening. FUNDING: Cincinnati Children's Research Foundation.

Characteristics of a rapid, point-of-care lateral flow immunoassay for the diagnosis of sickle cell disease.

Sickle cell disease (SCD) is a common and life-threatening hematological disorder, affecting approximately 400,000 newborns annually worldwide. Most SCD births occur in low-resource countries, particularly in sub-Saharan Africa, where limited access to accurate diagnostics results in early mortality. We evaluated a prototype immunoassay as a novel, rapid, and low-cost point-of-care (POC) diagnostic device (Sickle SCAN) designed to identify HbA, HbS, and HbC. A total of 139 blood samples were scored by three masked observers and compared to results using capillary zone electrophoresis. The sensitivity (98.3-100%) and specificity (92.5-100%) to detect the presence of HbA, HbS, and HbS were excellent. The test demonstrated 98.4% sensitivity and 98.6% specificity for the diagnosis of HbSS disease and 100% sensitivity and specificity for the diagnosis of HbSC disease. Most variant hemoglobins, including samples with high concentrations of HbF, did not interfere with the ability to detect HbS or HbC. Additionally, HbS and HbC were accurately detected at concentrations as low as 1-2%. Dried blood spot samples yielded clear positive bands, without loss of sensitivity or specificity, and devices stored at 37°C gave reliable results. These analyses indicate that the Sickle SCAN POC device is simple, rapid, and robust with high sensitivity and specificity for the detection of HbA, HbS, and HbC. The ability to obtain rapid and accurate results with both liquid blood and dried blood spots, including those with newborn high-HbF phenotypes, suggests that this POC device is suitable for large-scale screening and potentially for accurate diagnosis of SCD in limited resource settings.

Hemoglobin variants identified in the Uganda Sickle Surveillance Study.

The Uganda Sickle Surveillance Study analyzed dried blood spots that were collected from almost 100 000 infants and young children from all 10 regions and 112 districts in the Republic of Uganda, with the primary objective of determining the prevalence of sickle cell trait and disease. An overall prevalence of 13.3% sickle cell trait and 0.7% sickle cell disease was recently reported. The isoelectric focusing electrophoresis technique coincidentally revealed numerous hemoglobin (Hb) variants (defined as an electrophoresis band that was not Hb A, Hb F, Hb S, or Hb C) with an overall country-wide prevalence of 0.5%, but with considerable geographic variability, being highest in the northwest regions and districts. To elucidate these Hb variants, the original isoelectric focusing (IEF) gels were reviewed to identify and locate the variant samples; corresponding dried blood spots were retrieved for further testing. Subsequent DNA-based investigation of 5 predominant isoelectric focusing patterns identified 2 α-globin variants (Hb Stanleyville II, Asn78Lys; Hb G-Pest, Asp74Asn), 1 ß-globin variant (Hb O-Arab, Glu121Lys), and 2 fusion globin variants (Hb P-Nilotic, ß31-δ50; Hb Kenya, Aγ81Leu-ß86Ala). Compound heterozygotes containing an Hb variant plus Hb S were also identified, including both Hb S/O-Arab and HbS/Kenya. Regional differences in the types and prevalence of these hemoglobin variants likely reflect tribal ancestries and migration patterns. Algorithms are proposed to characterize these Hb variants, which will be helpful for emerging neonatal hemoglobinopathy screening programs that are under way in sub-Saharan Africa.

Whole exome sequencing identifies novel genes for fetal hemoglobin response to hydroxyurea in children with sickle cell anemia.

Hydroxyurea has proven efficacy in children and adults with sickle cell anemia (SCA), but with considerable inter-individual variability in the amount of fetal hemoglobin (HbF) produced. Sibling and twin studies indicate that some of that drug response variation is heritable. To test the hypothesis that genetic modifiers influence pharmacological induction of HbF, we investigated phenotype-genotype associations using whole exome sequencing of children with SCA treated prospectively with hydroxyurea to maximum tolerated dose (MTD). We analyzed 171 unrelated patients enrolled in two prospective clinical trials, all treated with dose escalation to MTD. We examined two MTD drug response phenotypes: HbF (final %HbF minus baseline %HbF), and final %HbF. Analyzing individual genetic variants, we identified multiple low frequency and common variants associated with HbF induction by hydroxyurea. A validation cohort of 130 pediatric sickle cell patients treated to MTD with hydroxyurea was genotyped for 13 non-synonymous variants with the strongest association with HbF response to hydroxyurea in the discovery cohort. A coding variant in Spalt-like transcription factor, or SALL2, was associated with higher final HbF in this second independent replication sample and SALL2 represents an outstanding novel candidate gene for further investigation. These findings may help focus future functional studies and provide new insights into the pharmacological HbF upregulation by hydroxyurea in patients with SCA.

Genetic modifiers of sickle cell anemia in the BABY HUG cohort: influence on laboratory and clinical phenotypes.

The recently completed BABY HUG trial investigated the safety and efficacy of hydroxyurea in infants with sickle cell anemia (SCA). To investigate the effects of known genetic modifiers, genomic DNA on 190 randomized subjects were analyzed for alpha thalassemia, beta-globin haplotype, polymorphisms affecting endogenous fetal hemoglobin (HbF) levels (XmnI, BCL11A, and HBS1L-MYB), UGT1A1 promoter polymorphisms, and the common G6PD A(-) mutation. At study entry, infants with alpha thalassemia trait had significantly lower mean corpuscular volume, total bilirubin, and absolute reticulocyte count. Beta-globin haplotypes associated with milder disease had significantly higher hemoglobin and %HbF. BCL11A and XmnI polymorphisms had significant effects on baseline HbF, while UGT1A1 promoter polymorphisms significantly influenced baseline serum bilirubin. At study exit, subjects randomized to placebo still exhibited laboratory effects of alpha thalassemia and other modifiers, while those assigned hydroxyurea had treatment effects that exceeded most genetic influences. The pain phenotype was influenced by HbF modifiers in both treatment groups. These data document that genetic polymorphisms do modify laboratory and clinical phenotypes even in very young patients with SCA. The hydroxyurea effects are more potent, however, indicating that treatment criteria should not be limited to certain genetic subsets, and supporting the use of hydroxyurea for all young patients with SCA.