Global epidemiology of sickle haemoglobin in neonates: a contemporary geostatistical model-based map and population estimates

Abstract

SummaryBackgroundReliable estimates of populations affected by diseases are necessary to guide efficient allocation of public health resources. Sickle haemoglobin (HbS) is the most common and clinically significant haemoglobin structural variant, but no contemporary estimates exist of the global populations affected. Moreover, the precision of available national estimates of heterozygous (AS) and homozygous (SS) neonates is unknown. We aimed to provide evidence-based estimates at various scales, with uncertainty measures.MethodsUsing a database of sickle haemoglobin surveys, we created a contemporary global map of HbS allele frequency distribution within a Bayesian geostatistical model. The pairing of this map with demographic data enabled calculation of global, regional, and national estimates of the annual number of AS and SS neonates. Subnational estimates were also calculated in data-rich areas.FindingsOur map shows subnational spatial heterogeneities and high allele frequencies across most of sub-Saharan Africa, the Middle East, and India, as well as gene flow following migrations to western Europe and the eastern coast of the Americas. Accounting for local heterogeneities and demographic factors, we estimated that the global number of neonates affected by HbS in 2010 included 5 476 000 (IQR 5 291 000–5 679 000) AS neonates and 312 000 (294 000–330 000) SS neonates. These global estimates are higher than previous conservative estimates. Important differences predicted at the national level are discussed.InterpretationHbS will have an increasing effect on public health systems. Our estimates can help countries and the international community gauge the need for appropriate diagnoses and genetic counselling to reduce the number of neonates affected. Similar mapping and modelling methods could be used for other inherited disorders.FundingThe Wellcome Trust.

Time to Invest in Sickle Cell Anemia as a Global Health Priority

“…4 For the 1% to 2% of these births that occur in high resource settings, SCA is identified early through newborn screening (NBS) programs and early-life threatening complications are avoided through early access to care. In countries with established NBS and treatment programs, death during childhood is a rare event with >90% of children with SCA surviving to adulthood.…”

“…Of the estimated 312 000 annual homozygous hemoglobin SS births, >90% occur in low-resource settings, with an estimated 238 000 annual births in sub-Saharan Africa and >46 000 in India. 4 The incidence of SCA is likely ∼1% to 2% among newborns across the sub-Saharan region, with the highest number of births in the most populous countries of the Democratic Republic of Congo and Nigeria. In these settings, estimates suggest that up to 90% of infants with SCA will die before their fifth birthday.…”

Prevention of sickle cell disease: observations on females with the sickle cell trait from the Manchester project, Jamaica

“…Sickle cell disease is the most common genetic disorder and the generally most severe form, SS disease, affects an estimated 240,000 births annually in sub-Saharan Africa (Piel et al 2013). Births with sickle cell disease may be avoided by prenatal or pre-implantation diagnosis, but these are costly and often limited to developed societies.…”

Perspective: We need a global solution

“…Using geostatistical models, epidemiologists estimate that more than 300,000 babies with two copies of the sickle haemoglobin gene are born every year 1 . This is probably an underestimate, but it provides the best current approximation of populations afflicted with the disease.…”