PB2141 FEATURES OF THE DIRECT ANTIGLOBULIN TEST IN PATIENTS WITH MULTIPLE MYELOMA

Abstract

Background:The direct antiglobulin test (DAT) is used to detect autoantibodies that are fixed on the surface of red blood cells. A differentiated DAT allows to estimate the amount of absorbed immunoglobulins, describe their class and subclass, and detect the components of the complement on the membrane of red blood cells. This information helps to predict the risk of hemolysis and suggest the cause of anemia in a particular patient.Aims:To study the frequency and features of positive DAT in patients with multiple myeloma (MM).MethodsThe results of differentiated DAT were analyzed in 80 patients first hospitalized at the Institute clinic in 2018–2019 with the diagnosis MM. DAT was performed by gel method using anti‐IgG/C3d, DC‐Screening I and DAT IgG1/IgG3 cards (BioRad, USA). The frequency of positive DAT in patients was compared with the same in 200 healthy residents of the region–donors of blood components.Results:All blood donors were DAT‐negative. Autoantibodies to red blood cells were detected in 27.5% (22) of patients with MM (p < 0.05).The intensity of the reaction (+) was observed in 50.0% (11) of patients with positive DAT, (++)–in 50.0% (11). DAT (++ + ), (++ + +) was not revealed. In the 100% of cases immunoglobulins G subclasses 2,4 were fixed on the surface of red blood cells, associated with a low risk of immune hemolysis. None of the patients was positive due to immunoglobulins classes A, M and complement components, which could contribute to the development of hemolytic complications. No clinical and laboratory signs of hemolysis were observed in the patients with positive DAT.Positive DAT was more frequently found in the group of patients with MM older than 60 years (48.0%), whereas in the group of patients younger than 60 years it was 18.2% (p <0.05).When observing patients with MM with positive DAT, it was noted that in one third of patients receiving chemotherapy, the result of DAT becomes negative within 5 months.Autoantibodies can interact with test and donors red blood cells, being detected in an indirect antiglobulin test (IAT). Positive IAT was in 9.1% of patients with positive DAT and in 3.4% ‐ with negative. These patients had difficulties in donor's selection due to non‐specific agglutination.Summary/Conclusion:Even though positive DAT is often found in patients with MM, not in every case it should be regarded as a sign of autoimmune hemolysis. To correctly assess the risk of hemolysis, physicians should analyze other laboratory and clinical data. Positive DAT may be correlated with the difficulties of selection of the donor for such patient.