Sickle cell disease in the Zanzibar Archipelago, the Republic of Tanzania.

Background: Sickle cell disease (SCD) is one of the most severe haemoglobinopathies, a group of blood disorders, typically inherited. The condition affects over 7.7 million people globally and results in more than 370,000 deaths per year. The highest morbidity and mortality rates are seen in Africa and most children with SCD are born in Tanzania. The available literature on SCD morbidity in Tanzania focus primarily on the residents of the mainland, while there is little data available on SCD morbidity among residents of the Tanzanian islands in the Indian Ocean. The aim of the present study was to confirm the presence of sickle cell disease among residents of the Zanzibar Archipelago.

Material and methods: The study group consisted of 27 people, residents of Pemba Island in the Zanzibar Archipelago, aged between 2 months and 26 years old, whose at least one parent has been diagnosed with sickle cell anaemia. Blood samples collected from the study participants were tested using HemoTypeSCTM, a rapid, point-of-care diagnostic test. The tests were performed at the Amal Hospital (Chake Chake town, Pemba Island) in June 2023.

Results: Sickle cell disease was diagnosed in 11 study subjects (40.7%); their haemoglobin concentration ranged between 6.6 and 8.5 g/dL. The presence of the sickle cell trait (HbAS phenotype) was confirmed in 14 patients (51.9%). Only two of the tested patients had normal haemoglobin phenotype.

Conclusions: The results of the present study support the necessity to introduce large-scale population- -based screening for SCD in the Zanzibar Archipelago, especially in infants whose family members have sickle cell anaemia. The introduction of such a programme will help monitor the number of new SCD cases in the region and may potentially reduce infant mortality due to SCD as well as minimize complications from SCD in older children through the adoption of effective disease prevention measures.