Comparison between the Conventional Tube Technique and the Gel Technique in Direct Antiglobulin Tests

Objectives: The direct antiglobulin test (DAT) is a diagnostic procedure demonstrating in-vivo antibody or complement coating on red cells. The gel technique (GT) for this test is sensitive and easier to do than the conventional tube technique (CTT). Methods: We tested 52 newborns with hyperbilirubinemia and 6 children and 17 adults with autoimmune hemolytic anemia (AIHA) using the (DAT) in the form of the conventional tube technique (CTT) and the gel technique (GT) simultaneously. The gradings of the agglutination reactions of both techniques were scored as 12, 10, 8, 5, 3, 0 for 4+, 3+, 2+, 1+ and w+ and negative, respectively. Results: The GT yielded higher scores than the CTT (p < 0.01). The overall sensitivity and specificity of the GT were 93.5 and 88.6%, respectively. The specificity of the DAT-positive results in newborns was determined by IgG only, while in AIHA, it was determined by IgG and/or C3d and, in only one sample, by IgM. Conclusion: The GT is equal to or better than the CTT. Since the GT is simple, the exposure of blood bank personnel to the blood sample is low. We highly recommend the GT, especially in areas where HIV infection is prevalent.