Surveillance for sickle cell disease, United Republic of Tanzania

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

Perceptions and preferences for genetic testing for sickle cell disease or trait: a qualitative study in Cameroon, Ghana and Tanzania

Sickle cell disease (SCD) is a single gene blood disorder characterised by frequent episodes of pain, chronic anaemic, acute chest syndrome, severe disease complications and lifelong debilitating multi-system organ damage. Genetic testing and screening programs for SCD and the sickle cell trait (SCT) are valuable for early diagnosis and management of children living with SCD, and in the identification of carriers of SCT. People with SCT are for the most part asymptomatic and mainly identified as through genetic testing or when they have a child with SCD. This qualitative study explored perceptions towards genetic testing for SCD and SCT in Cameroon, Ghana, and Tanzania. The results show a general preference for newborn screening for SCD over prenatal and premarital/preconception testing, primarily due to its simpler decision-making process and lower risk for stigmatization. Premarital testing for SCT was perceived to be of low public health value, as couples are unlikely to alter their marriage plans despite being aware of their risk of having a child with SCD. Adolescents were identified as a more suitable population for SCT testing. In the case of prenatal testing, major concerns were centred on cultural, religious, and personal values on pregnancy termination. The study revealed a gender dimension to SCD/SCT testing. Participants mentionned that women bear a heightened burden of decision making in SCD/SCT testing, face a higher risk of rejection by potential in-laws/partners if the carriers of SCT, as well as the possibility of  divorce if they have a child with SCD. The study highlights the complex cultural, ethical, religious and social dynamics surrounding genetic testing for SCD and emphasises the need for public education on SCD and the necessity of incorporating genetic and psychosocial counselling into SCD/SCT testing programs.

Impact of Sickle Cell Awareness Day on online health information seeking in Africa using Google Trends

The United Nations Council Assembly recognized sickle cell disease (SCD) as a global public health problem due to its increasing burden, particularly in sub-Saharan Africa. To raise awareness, a resolution was adopted, designating June 19th as SCD awareness day. However, the impact of this awareness day on online health information seeking behaviour (OHISB) in African countries is not well understood, especially in Nigeria, Ghana and Uganda where SCD prevalence is high. To assess the impact, the study used Google Trends data as a measure of OHISB for SCD. The analysis covered the 60 days before the awareness day, the awareness day itself, and the 60 days afterward. Time series analysis was conducted using joinpoint regression to identify significant changes in OHISB trends. The results indicated that the impact of the Sickle Cell Awareness Day on OHISB varied across African countries and did not consistently inspire significant changes in information seeking behaviour. This suggests the need for more targeted awareness campaigns to improve public knowledge of SCD in Africa. It also highlights the importance of revising the current awareness day or creating alternative health awareness initiatives that adopt a long-term approach and address the specific health needs of the African population. Furthermore, due to limitations in using Google Trends data in some African countries with insufficient data, future research should explore other sources of internet data or conduct surveys to gain a more comprehensive understanding of the impact of the Sickle Cell Awareness Day on OHISB in Africa.

Systematic Literature Review Shows Gaps in Data on Global Prevalence and Birth Prevalence of Sickle Cell Disease and Sickle Cell Trait: Call for Action to Scale Up and Harmonize Data Collection

Sickle cell disease (SCD) is an inherited monogenic disorder with high prevalence throughout sub-Saharan Africa, the Mediterranean basin, the Middle East, and India. Sources of SCD epidemiology remain scarce and fragmented. A systematic literature review (SLR) to identify peer-reviewed studies on SCD epidemiology was performed, with a search of bibliographic databases and key conference proceedings from 1 January 2010 to 25 March 2022 (congress abstracts after 2018). The SLR followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Meta-analyses, using a binomial normal random-effects model, were performed to estimate global and regional prevalence and birth prevalence. Of 1770 journal articles and 468 abstracts screened, 115 publications met the inclusion criteria. Prevalence was highest in Africa (~800/100,000), followed by the Middle East (~200/100,000) and India (~100/100,000), in contrast to ~30/100,000 in Europe. Birth prevalence was highest in Africa (~1000/100,000) and lowest in North America (~50/100,000) and Europe (~30/100,000). This SLR confirmed that sub-Saharan and North-East Africa, India, the Middle East, and the Caribbean islands are global SCD hotspots. Publications including mortality data were sparse, and no conclusions could be drawn about mortality. The identified data were limited due to gaps in the published literature for large parts of the world population; the inconsistent reporting of SCD genotypes, diagnostic criteria, and settings; and a sparsity of peer-reviewed publications from countries with assumed high prevalence. This SLR demonstrated a lack of systematic knowledge and a need to provide uniform data collection on SCD prevalence and mortality.

Global, regional, and national prevalence and mortality burden of sickle cell disease, 2000-2021: a systematic analysis from the Global Burden of Disease Study 2021

BACKGROUND

Previous global analyses, with known underdiagnosis and single cause per death attribution systems, provide only a small insight into the suspected high population health effect of sickle cell disease. Completed as part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021, this study delivers a comprehensive global assessment of prevalence of sickle cell disease and mortality burden by age and sex for 204 countries and territories from 2000 to 2021.

METHODS

We estimated cause-specific sickle cell disease mortality using standardised GBD approaches, in which each death is assigned to a single underlying cause, to estimate mortality rates from the International Classification of Diseases (ICD)-coded vital registration, surveillance, and verbal autopsy data. In parallel, our goal was to estimate a more accurate account of sickle cell disease health burden using four types of epidemiological data on sickle cell disease: birth incidence, age-specific prevalence, with-condition mortality (total deaths), and excess mortality (excess deaths). Systematic reviews, supplemented with ICD-coded hospital discharge and insurance claims data, informed this modelling approach. We employed DisMod-MR 2.1 to triangulate between these measures-borrowing strength from predictive covariates and across age, time, and geography-and generated internally consistent estimates of incidence, prevalence, and mortality for three distinct genotypes of sickle cell disease: homozygous sickle cell disease and severe sickle cell β-thalassaemia, sickle-haemoglobin C disease, and mild sickle cell β-thalassaemia. Summing the three models yielded final estimates of incidence at birth, prevalence by age and sex, and total sickle cell disease mortality, the latter of which was compared directly against cause-specific mortality estimates to evaluate differences in mortality burden assessment and implications for the Sustainable Development Goals (SDGs).

FINDINGS

Between 2000 and 2021, national incidence rates of sickle cell disease were relatively stable, but total births of babies with sickle cell disease increased globally by 13·7% (95% uncertainty interval 11·1-16·5), to 515 000 (425 000-614 000), primarily due to population growth in the Caribbean and western and central sub-Saharan Africa. The number of people living with sickle cell disease globally increased by 41·4% (38·3-44·9), from 5·46 million (4·62-6·45) in 2000 to 7·74 million (6·51-9·2) in 2021. We estimated 34 400 (25 000-45 200) cause-specific all-age deaths globally in 2021, but total sickle cell disease mortality burden was nearly 11-times higher at 376 000 (303 000-467 000). In children younger than 5 years, there were 81 100 (58 800-108 000) deaths, ranking total sickle cell disease mortality as 12th (compared to 40th for cause-specific sickle cell disease mortality) across all causes estimated by the GBD in 2021.

INTERPRETATION

Our findings show a strikingly high contribution of sickle cell disease to all-cause mortality that is not apparent when each death is assigned to only a single cause. Sickle cell disease mortality burden is highest in children, especially in countries with the greatest under-5 mortality rates. Without comprehensive strategies to address morbidity and mortality associated with sickle cell disease, attainment of SDG 3.1, 3.2, and 3.4 is uncertain. Widespread data gaps and correspondingly high uncertainty in the estimates highlight the urgent need for routine and sustained surveillance efforts, further research to assess the contribution of conditions associated with sickle cell disease, and widespread deployment of evidence-based prevention and treatment for those with sickle cell disease.

FUNDING

Bill & Melinda Gates Foundation.

Barriers and Facilitators of Availability of Hydroxyurea for Sickle Cell Disease in Tanzania; A Qualitative Study of Pharmaceutical Manufacturers, Importers, and Regulators

Despite three decades of proven safety and effectiveness of hydroxyurea in modifying sickle cell disease (SCD), its accessibility is limited in Sub-Saharan Africa, which shares 75% of the world's SCD burden. Therefore, it is time to explore the barriers and facilitators for manufacturing and importation of hydroxyurea for SCD in Tanzania. This was qualitative research that employed a case study approach. Purposive sampling followed by an in-depth interview (IDI) using a semi-structured questionnaire aspired by data saturation enabled us to gather data from 10 participants. The study participants were people with more than three years of experience in pharmaceuticals importation, manufacturing, and regulation. The audio-recorded data were verbatim transcribed and analyzed using thematic analysis. Two themes were generated. The first comprised barriers for importation and manufacturing of hydroxyurea with sub-themes such as inadequate awareness of SCD and hydroxyurea, limited market, and investment viability. The second comprised opportunities for importation and manufacturing of hydroxyurea with sub-themes such as awareness of activities performed by medicines regulatory authority and basic knowledge on SCD and hydroxyurea. Inadequate understanding of SCD, hydroxyurea, and orphan drug regulation are major issues that aggravate the concern for limited market and investment viability. Existing opportunities are a starting point towards increasing the availability of hydroxyurea.

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.

The effect of sickle cell genotype on the pharmacokinetic properties of artemether-lumefantrine in Tanzanian children

Since there are inconsistent data relating to the effect of haemoglobinopathies on disposition of artemisinin antimalarial combination therapy, and none in sickle cell trait (SCT) or sickle cell disease (SCD), the aim of this study was to characterize the pharmacokinetic properties of artemether-lumefantrine (ARM-LUM) in children with SCD/SCT. Thirty-eight Tanzanian children aged 5–10 years with normal (haemoglobin AA; n = 12), heterozygous (haemoglobin AS; n = 14) or homozygous (haemoglobin SS; n = 12) sickle genotypes received six ARM-LUM doses (1.7 mg/kg plus 10 mg/kg, respectively) over 3 days. Sparse venous and mixed-capillary dried blood spot (DBS) samples were taken over 42 days. Plasma and DBS ARM and LUM, and their active metabolites dihydroartemisinin (DHA) and desbutyl-lumefantrine (DBL), were assayed using validated liquid chromatography-mass spectrometry. Multi-compartmental pharmacokinetic models were developed using a population approach. Plasma but not DBS concentrations of ARM/DHA were assessable. The majority (85%) of the 15 measurable values were within 95% prediction intervals from a published population pharmacokinetic ARM/DHA model in Papua New Guinean children of similar age without SCD/SCT who had uncomplicated malaria, and there was no clear sickle genotype clustering. Plasma (n = 38) and corrected DBS (n = 222) LUM concentrations were analysed using a two-compartment model. The median [inter-quartile range] LUM AUC_0–∞ was 607,296 [426,480–860,773] μg.h/L, within the range in published studies involving different populations, age-groups and malaria status. DBS and plasma DBL concentrations correlated poorly and were not modelled. These data support use of the conventional ARM-LUM treatment regimen for uncomplicated malaria in children with SCT/SCD.

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Malaria remains a serious infection in children with sickle cell trait/disease.

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Artemether-lumefantrine (AL) is first-line therapy in this situation.

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There are no AL pharmacokinetic data in children with sickle cell disease/trait.

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AL disposition in Tanzanian children did not differ across sickle genotypes.

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Recommended AL treatment doses can be given regardless of sickle status.

Healthcare Workers' Knowledge and Resource Availability for Care of Sickle Cell Disease in Dar es Salaam, Tanzania

Background: Sickle cell disease (SCD) is a global public health priority due to its high morbidity and mortality. In Tanzania, SCD accounts for 7% of under-five mortality. Cost-effective interventions such as early diagnosis and linkage to care have been shown to prevent 70% of deaths but require knowledge among healthcare workers and availability of resources at health facilities. In Tanzania, data on these critical determinants are currently lacking. Objective: To assess healthcare workers' knowledge and resource availability for care of SCD at health facilities in Dar es Salaam, Tanzania. Methodology: A facility-based cross-sectional study was conducted between December 2020 and February 2021 among 490 nurses and clinicians at Regional Referral Hospitals (Temeke, Amana, and Mwananyamala) and Muhimbili National Hospital in Dar es Salaam, Tanzania. Data were collected using a pre-tested structured questionnaire consisting of 13 knowledge questions (scored good knowledge if correct response in >7) and an inventory check list to record available resources. Pearson's χ² was used to determine the association between level of knowledge and demographic factors. Multivariate logistic regression was used to ascertain the strength of associations. A two-tailed p-value <0.05 was considered to be statistically significant. Results: Of the 490 participants (median age 28 years [IQR = 26-35]), only 25.1% had good knowledge on SCD. The odds of good knowledge was 82% lower in nurses than clinicians (AOR = 0.177; 95% CI: 0.090, 0.349; p < 0.001); 95% lower in diploma than Master's degree holders (AOR = 0.049; 95% CI: 0.008, 0.300; p = 0.001) and 4.6 times higher in those with 5-9 years than ≥10 years of experience (AOR = 4.564; 95% CI: 1.341, 15.525; p = 0.015). The regional-level hospitals lacked diagnostic tests and hydroxyurea therapy. Conclusion: There was general lack of knowledge on SCD among healthcare workers and limited availability of critical resources for the diagnosis and care of SCD, especially at regional-level hospitals. Efforts are needed for their improvement to enhance care to patients, thus reducing the morbidity and mortality due to SCD in Tanzania.