RESUMO
Unexpected antibodies, also called irregular antibodies, are not known to exist in a person's serum before testing. This research aims to assess the prevalence of unexpected antibodies and their correlation with several clinical conditions. This cross-sectional prospective study, undertaken from June 2019 to June 2020, included ABO, Rh grouping, cross-matching, and antibody screening. Antibody identification was performed only on patients who tested positive in the screening test. From a total of 9764 participants who were screened for unexpected antibodies, 107 (1.1%) tested positive. The Rh blood group system antibodies were the most frequent, particularly anti-D. There was also a significant correlation between the unexpected antibodies and history of transfusion, pregnancy, and autoimmune diseases as P ≤ 0.05. The most prominent unexpected antibodies in the study belong to the Rh system (Anti-D). Moreover, as a result of the strong correlation between the unexpected antibodies as well as the history of transfusion, pregnancy, and autoimmune diseases, the highest safety criteria must be followed during the transfusion of blood to patients with these clinical conditions.