Anti-erythrocytes are complex proteins, produced in response to one or more epitopes on the surface of red blood cells are regular or irregular. The screening irregular antibodies based on the Indirect Antiglobulina Test (IAT) method aims to observe in vitro the antibodies present in the bloodstream against red blood cells with known antigen profiles. Which are selected based on the main antigens of the blood group system (D, C, E, c, e, M, N, S, s, P1, Le a, Le b, K, k,Fy a, Fy b, Jk a, Jk b and Di a). The presence of irregular alloantibodies in blood donors is of clinical importance due to their immunogenicity.

To investigate the prevalence of irregular antibodies in blood donors from the Institute of Hematology and Hemotherapy of Amapá.

Prospective observational study of the prevalence of irregular antibodies in blood donors from the Institute of Hematology and Hemotherapy of Amapá, from October 2022 to June 2023. The samples was obtained from voluntary donors, able to donate, between 18 and 69 yearsold, both sexes, with formal consent for routine laboratory tests. The tests was performed by the agglutination method on a gel card followed by centrifugation, with ID-Diacell Pollsuspension of red blood cells at 0.8%±0.1, microwells with gel containing rabbit anti-humanglobulin and C3d monoclonal ID-Card Liss/Coombs, vials of ID-Diapanel test RBCs(Diamed Latino América S.A).

During the studied period, 10.029 blood donors was registered in the HEMOVIDA System, 63.5% (n = 6.371) male e 36.5% (n = 3.658) female, 10/10.029 (0.1%) donors with PositiveScreening irregular antibody , 1 (1/10, 10%) male and 9 (9/10, 90%) female. The Identified antibodies: anti-D (40%; n = 04), anti-Di a (20%; n = 02), anti-Kp a (10%; n = 01), anti-K (10%; n = 01), anti-N (10%; n = 01), anti-k (10%; n = 01). No antibody association were detected in thestudied samples. Antibody specificities were mostly identified in female, with the exceptionof anti-N (10%; n = 01) found in male donors.

The occurrence of irregular antibodies in the general population is 0.3% to 2.0. Although thesample size of this study was relatively proportional to the number of blood donors ah theblood center, compared to the state population, it provides an estimate of irregular antibodyfrequencies in blood donors from the Amazon. However, more research is needed for a morecomprehensive understanding of the frequency of irregular antibodies in different blooddonors populations.

The genetic pool of people who migrate to Amapá has a strong relationship withmiscegenation of erythrocyte antibodies found in the population. Large-scale studies areneeded to assess the magnitude of irregular antibodies in blood donors and assess theirclinical impact on the recipient population.