Abstract
The hospital blood bank plays a key role in the diagnosis of acute transfusion reactions involving red cell incompatibility. This paper discusses the interpretation of the serological tests performed by the laboratory. Because red cell incompatible transfusion reactions occur so infrequently it is difficult to accumulate practical experience in their laboratory presentation and this paper describes several of the pitfalls that may be encountered when laboratory findings deviate from classical descriptions. These include the absence of a positive direct antiglobulin test (Coombs) or an incompatible crossmatch, the absence of any apparent discrepancy between the pre- and posttransfusion specimens in cases of ABO incompatibility, the differentiation of auto-immune haemolytic anaemia from delayed transfusion reactions and the assessment of the clinical significance of any blood group antibodies that may be detected.