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Investigators use an indirect approach to estimate the mortality rate of children with sickle cell anemia in sub-Saharan Africa because there's no systematic screening at birth.
Although sickle cell disease (SCD) is classified as a rare disease in the US, in sub-Saharan Africa, it’s a completely different story. According to a study conducted by Piel FB and a team of investigators, 300,000 babies are born with sickle cell disease each year in sub-Saharan Africa, and that number is expected to increase to 400,000 by 2050.
The heaviest burden of sickle cell disease is in this region. Sickle cell disease has been designated as a global public health problem by the World Health Organization (WHO) and United Nations (UN).
Because of this, Brigitte Ranque, MD, Service de Médecine Interne, Hôpital Européen Georges Pompidou, Assistance Publique–Hôpitaux de Paris, along with a team of investigators, decided to estimate the risk of child mortality attributable to sickle cell anemia in these countries with a retrospective, multicenter, case-controlled study.
Investigators took an indirect approach to evaluate the child mortality rate of sickle cell anemia in order to overcome the lack of systematic screening at birth. According to the study, the lifespan of patients with the disease has markedly improved over the last 40 years–in high-income countries.
Alternatively, in sub-Saharan Africa, it’s still expected that most children born with sickle cell disease will die before their fifth birthday. However, investigators noted that no direct epidemiological study has described mortality rates from birth.
Previous cohort studies that included patients with SCD who followed up in African sickle cell disease expert centers indicated a lower mortality estimate. However, investigators pointed out that most of the children were diagnosed several years after birth–therefore overlooking the infants who died before receiving a diagnosis.
Coming to an estimate of sickle cell anemia-related infant (< 1 year) and child (< 5 years) mortality by conventional methods in this population wasn’t feasible due to the absence of systematic screening at birth and a death registry. Of sub-Saharan Africa, 5 countries were included in the investigation, Burkina Faso, Democratic Republic of the Congo, Côte d’Ivoire, Mali, and Senegal.
In this retrospective case-controlled study, investigators specifically looked for women who had at least 1 child with a confirmed SS hemoglobin phenotype and at least 3 children (alive or deceased) from the same father as the child with sickle cell anemia who was born more than 5 years ago. Families with a parent diagnosed with SCD were excluded.
As for the control group, inclusion requirements included being a neighbor or relative of a mother in the non-control group, having no child or first-degree relative with hemoglobin SS, SC, or S beta thalassaemia, having at least 3 children (alive or deceased) born more than 5 years ago, and having a confirmed hemoglobin AA phenotype determined by point-of-care testing.
The primary objective was to estimate the relative risk of mortality associated with sickle cell anemia in children younger than 5 years of age. Secondary objectives were to estimate this same risk in infants and children younger than 10 years, and to identify socioeconomic and geographical prognostic factors of mortality in these populations.
The global Multidimensional Poverty Index (MPI) was utilized with 10 indicators on education, health, and standards of living in the household.
“We assumed a mortality in children younger than 5 years of 8% in the control group and 30% in children with sickle cell anaemia—ie, 15% in families with cases of sickle cell anaemia,” investigators wrote. “To obtain a precision of 95% CI narrower than 2% in the mortality rate, with 90% power and 5% α risk, at least 4896 children born more than 5 years ago had to be recruited in families with cases of sickle cell anaemia and 3456 in control families.”
The estimated rates of mortality for sickle cell anemia were 15.3% (95% CI, 13.3-17.3) for infants, 36.4% (33.4-39.4) for children younger than 5 years old, and 43.3% (39.3-47.3) for those under the age of 10.
After exclusions, 1315 families with cases of sickle cell anemia and 1243 control families were included in the assessment. It was observed in the Kaplan-Meier survival analysis that children in families with cases of sickle cell anemia died earlier than the children in control families.
This research estimated a 5.35 time higher mortality rate in children under the age of 5 with sickle cell anemia when compared with children from the control families in sub-Saharan Africa. This estimate is lower than the estimate established in published literature but the mortality rate in this population of children is still high compared with the rate in high-income countries.
“Our results show the substantial improvement in quality of health care provided to children with sickle cell anaemia in hospitals in sub-Saharan Africa, but also underline the strong effect of the remaining pejorative socioeconomic factors that are not specific to sickle cell anaemia,” investigators concluded. “Because this study provides an estimate of mortality in a specific population, there is a need to fund prospective studies including children diagnosed with sickle cell disease at birth, especially for patients living in rural areas.”
The study “Estimating the risk of child mortality attributable to sickle cell anaemia in sub-Saharan Africa: a retrospective, multicentre, case-control study” was published in The Lancet Haematology.