Mitogen-stimulated DAT: a new method for the diagnosis of AIHA

Background. Direct antiglobulin test (DAT), the hallmark of autoimmune haemolytic anaemia (AIHA), can be performed with different laboratory techniques, which have variable sensitivity and/or specificity. In a minority of patients, named DAT-negative AIHA, the diagnosis is made in exclusion. We recently described a new method for the detection of anti-RBC antibodies in mitogenstimulated whole blood cultures, named mitogenstimulated-DAT (MS-DAT). Aim. To investigate the prevalence of MS-DAT positivity in a larger series of DAT-positive and DATnegative AIHA at different states of disease activity, and in B-CLL with or without DAT-positive AIHA. Materials and methods. We studied 33 DAT-positive AIHA with different disease activity, 7 DAT-negative AIHA, and 69 B-CLL patients. MS-DAT was performed by stimulating whole blood cultures with mitogens, and anti-RBC antibodies were detected by competitive solid phase ELISA. Standard DAT was performed with tube test, in solid phase and with enhancing solutions. Results. MS-DAT was positive in 6 DAT-negative patients with a history of DAT-positive AIHA, who were in clinical and laboratory remission at the moment of the study, and in 7 DAT-negative haemolytic anaemias, diagnosed as autoimmune in exclusion. MS-DAT was positive in 1/3 of the B-CLL patients without haemolytic features. MS-DAT was routinely performed during the follow-up of AIHA patients, and its values correlated with the clinical course, haemolytic parameters and response to therapy. Introduzione