Incidence and risk factors for vaso occlusive crisis among children living with sickle cell disease in Uganda: a cohort study

Background Vaso-occlusive crises (VOC) are the most frequent complications among people living with sickle cell disease. VOC lead to frequent hospitalisations, reduce quality of life and contribute to long-term sequelae such as stroke, acute chest syndrome, and renal impairment. There are limited contemporary data on the incidence and risk factors for VOC among children with sickle cell anaemia (SCA) after the introduction of hydroxyurea in Uganda. Methods A prospective cohort study conducted among children living with SCA enrolled in the Uganda Sickle Pan-African Research Consortium Registry, at the Mulago Hospital Sickle Cell Clinic. Participants aged 6 months to 18 years enrolled and followed for six months to assess the occurrence of VOC. Cox proportional hazards regression was used to evaluate associations between clinical and laboratory variables and time to VOC. Results A total of 438 participants were enrolled, with a median age of 9 years (IQR: 5–13). Most participants (80.1%) reported hydroxyurea use. The mean baseline haemoglobin concentration was 7.7 g/dL (SD: 1.2), and the median foetal haemoglobin (HbF) level was 12.3% (IQR: 7.2–18.2). in the preceding year, history of VOC was reported by 88.8%, and 30.1% had received at least one blood transfusion. The incidence of VOC was 102.3 (95% CI: 88.2–118.8) per 100 person-years, with 13% experiencing more than one episode during follow-up. After adjusting for sex and prior VOC history, previous blood transfusion was independently associated with increased VOC risk (aHR: 1.11; 95% CI: 1.02–1.22; p  = 0.020). Conclusion VOC remains a common and clinically significant complication among Ugandan children living with SCA. Prior blood transfusion was identified as a potential predictor of VOC, underscoring the need for optimised clinical management, including timely and appropriately dosed hydroxyurea therapy, to mitigate risk in this population.