LAUSR

BACKGROUND One of the strategies used to reduce the risk of haemolysis due to ABO-minor incompatible platelet transfusions is to perform a screening test to identify group O donors with high titres of anti-A and anti-B. However, critical immunoglobulin M/ immunoglobulin G (IgM/IgG) titres remain unclear. OBJECTIVE This study aimed to determine IgM titres of anti-A and anti-B in individual donor serum vs platelet products plasma and identify a possible association between IgM/IgG titres, haemolysin test and IgG subclasses in Brazilian blood donors from group O. METHODS IgM anti-A and Anti-B titration tests were performed on single-donor serum and platelet product plasma by gel agglutination (GA) at room temperature. For IgG anti-A and anti-B titration, serum was first treated with 0.01 M dithiothreitol (DTT), and the test was performed by GA with incubation at 37°C. Dilution of 1:64 as the cut-off was considered for both IgM/IgG. The qualitative haemolysin test was performed in tube, adding AB fresh serum, with incubation at 37°C. IgG subclasses were determined by GA using specific monoclonal antibodies. RESULTS An association between anti-A and anti-B IgM titres and haemolysin were demonstrated (P < .001). IgM titres in plasma samples from platelet components correlated to those in single-serum samples. IgG1/IgG3 subclasses were associated with total haemolysis and titres above 64, whereas IgG2/IgG4 subclasses were associated with the absence of haemolysis and titres below 64 (P < .001). CONCLUSION Our data suggest that a value of 64 as a critical titre can be used as a screening test of anti-A and anti-B IgM to prevent transfusion reactions. This can be a safe and cost-effective approach for managing ABO-incompatible platelet transfusions.