Study Finds Clinical Significance of RBC Immunoglobulin G in Polytransfused Patients with Thalassemia

A new study has found that the use of flow cytometry may allow for more accurate detection of red blood cell (RBC) autoantibody formation in patients with thalassemia compared with a direct Coombs test, according to findings reported in Hematology.

Regular RBC transfusions are the standard of care for several types of thalassemia. One of the major consequences of transfusion is the formation of alloantibodies and autoantibodies against RBC antigens that can result in hemolysis and difficulty in cross-matching of blood.

The direct Coombs test is typically used to detect these immunoglobulin G (IgG) antibodies but it is not particularly sensitive, according to the study. Flow cytometry, on the other hand, has high accuracy, reproducibility, and sensitivity and therefore may have utility as a tool for detecting RBC-bound IgG.

The study authors wanted to determine the prevalence and clinical significances of RBC-bound IgG as detected by flow cytometry in polytransfused patients with thalassemia.

The study included 59 polytransfused patients with β-thalassemia disease and 30 individuals without thalassemia. A persistent or transient-positive direct Coombs test was seen in 8 patients with thalassemia (13.6%), whereas 34 patients (57.6%) had a positive flow cytometry (P <.001). There were 8 patients who were positive for both tests.

Approximately 34% of patients developed RBC alloantibodies. The 4 most frequent RBC alloantibodies were anti-E (55%), anti-Mia (40%), anti-Di(a) (25%), and anti-c (15%), respectively.

There was no significant difference in the presence of RBC-bound IgG between patients who were polytransfused with thalassemia and who developed RBC alloimmunization and those without RBC alloantibodies. Splenectomy and increased transfusion requirements were significantly associated with the presence of RBC-bound IgG but not with RBC alloantibody formation, according to the study.

The researchers concluded that flow cytometry had higher sensitivity for detecting RBC-bound IgG compared with the direct Coombs test in polytransfused patients with thalassemia, stating that “the presence of anti-RBC autoantibodies may cause an increase in transfusion requirements.” Furthermore, they noted that splenectomy is a risk factor for autoantibody formation.

Reference

• Thedsawad A, Taka O, Wanachiwanawin W, et al. Prevalence and clinical significances of red cell alloimmunization and red cell bound immunoglobulin G in polytransfused patients with thalassemias. https://www.tandfonline.com/doi/full/10.1080/16078454.2018.1549818?scroll=top&needAccess=true. Accessed October 21, 2019.