Certain variants of the RhD antigen can produce false negative results in routine serologic testing, leading to unnecessary use of hemolytic disease of the fetus and newborn (HDFN) prophylaxis and overuse of D-negative units for transfusion, according to a recently published study in Immunohematology.
The leading cause of severe HDFN is RhD alloimmunization, a process in which an RhD-negative mother produces antibodies against the RhD antigen present in the red blood cells (RBCs) of a fetus during birth or in a blood unit during transfusion. To prevent immunization in RhD-negative women, doctors usually use HDFN prophylaxis through RHIG administration during gestation and after birth.
Learn more about HDFN testing and diagnosis
However, patients with certain antigen variants can falsely appear RhD negative during routine serological tests. Among the different RhD variants, it is essential to distinguish between two main groups: weak RhD variants and partial RhD variants. Patients with weak D are not at risk of alloimmunization, while patients with partial D are.
D variants vary in frequency among populations and ethnic groups, so there is a growing need for regional studies that determine the frequency of D variants in specific populations and how these variants behave in routine serologic tests.
Therefore, the authors aimed to assess the most frequent D variants and determine which were more likely to produce false negatives in serologic tests in the state of Sao Paulo, Brazil.
The study gathered blood samples and tested them through two routinely performed serologic and molecular tests to detect false negatives in routine serologic tests.
The authors found discrepancies between serologic and molecular results in most of the 37 samples; they observed that the variant most commonly associated with discrepancy was the weak D variant 38.
“The results highlight the importance of selecting tests for donor screening capable of detecting weak D types 38 and 11, especially in populations where these variants are more prevalent,” the authors wrote .“In pre-transfusion testing, it is crucial that D typing reagents demonstrate weak reactivity with DAR variants; having a serologic strategy to recognize DIVa and DIIIc is also valuable,”.
