2.1 Study design and setting
This was a cross-sectional study that included 164 individuals who were rejected for blood donation at the Instituto Nacional de Sangue (INS), a reference health unit, located in Luanda, the capital city of Angola, between March to May 2022. The study was carried out at Centro de Investigação em Saúde de Angola (CISA), a research institution supported by the Instituto Nacional de Investigação em Saúde (INIS), also located in Luanda. The INIS is a public institution of the Angolan Ministry of Health (MoH), which develops research in the most diverse areas of health and its determinants, to contribute to the strengthening of public health policies in Angola. This study was approved by the National Ethics Committee of the Angolan MoH (nr. 39/2021) and the direction board of the INS (nr.128/GDG/INS/2022). Participants were informed about the objectives of the study and verbal consent was obtained from all enrolled even before they were considered part of the study.