The sociodemographic profile of blood donors in Brazil has evolved over time, directly influenced by the high level of admixture in the population. The D antigen is considered to be among the most immunogenic in the field of transfusion medicine, and accurate identification is essential to prevent alloimmunization. Consequently, the accurate characterization donors with D phenotypes and their variants is critical for ensuring the safety and efficacy of the blood supply. The analysis of sociodemographic variables, including age, sex, and ethnicity, has been demonstrated to facilitate the identification of donation patterns and the detection of potential gaps in screening admixed populations, particularly among individuals expressing atypical D variants.

To describe the sociodemographic profile of D‑positive blood donors at the Amazonas State Hematology and Hemotherapy Foundation (HEMOAM) who exhibited atypical serological D phenotypes.

Samples were collected from repeat donors at HEMOAM between August 2024 and July 2025. Serological D phenotyping was performed using gel‑card and tube techniques. The sociodemographic variables analysed included sex, age, self‑declared ethnicity, place of birth, and ABO blood group.

A total eight cases (0.44%) of atypical D antigen typing were identified. The majority of donors were male (87.5%), with a mean age of 32 ±12 years old (range: 21–40 years). The self‑declared ethnicity of the subjects was as follows; 62.5% mixed‑race, 25% white, and 12.5% black. It is important to note that all donors were native to the Amazonas state. With regard to the ABO blood groups, an equal proportion of the population was observed to be either O or A, with a proportion of 50% for each blood group.

The profile of donors exhibiting atypical D phenotypes in our study demonstrates a notable predominance of male and mixed‑race donors, a finding that aligns with observations reported from other regions, including São Paulo, Minas Gerais, Pernambuco, Rio de Janeiro, and Pará. The age of donors corresponds to trends observed in the Central-West region of Brazil, with a notable concentration of younger donors (18-34 years old), reflects patterns seen in Minas Gerais and Pernambuco. This demographic profile mirrors the typical young male Brazilian donor demographic. The observed predominance of blood group O and A exceeds national averages (O: 45%, A: 42%, B: 10%, AB: 3%) and also surpasses figures reported from Mato Grosso and São Paulo. The elevated frequency of the group O blood type in the State of Amazonas may be indicative of contributions from the genetic heritages of indigenous populations, African communities, and European settlers. These findings emphasize the necessity of incorporating regional genetic particularities into serological testing protocols. This study identifies a predominant sociodemographic profile of adult mixed‑race men in Amazonas, capturing both regional admixture and broader national donation patterns. The disproportionate representation of blood groups O and A further suggests a strong Amazonian genetic component. These results underscore the necessity for bespoke serological protocols to ensure transfusion safety in admixed populations and reinforce the value of region‑specific epidemiological studies in characterizing D variant frequencies.