AMT Medical Laboratory Scientist (MLS) 2025 – 400 Free Practice Questions to Pass the Exam

The primary goal of Du or weak D testing is to determine who should receive anti-D immunoprophylaxis. This testing is essential in the context of Rh incompatibility, particularly during pregnancy or transfusion scenarios. Individuals who are weak D positive may have a minor expression of the D antigen on their red blood cells. If these individuals are exposed to Rh-positive blood—especially in the case of pregnancy with an Rh-positive fetus—they may produce antibodies against Rh-positive blood, which can lead to hemolytic disease of the newborn (HDN).

Identifying weak D is critical because, historically, weak D individuals might be treated as Rh-negative and given anti-D immunoglobulin as a preventative measure. Understanding who should receive this treatment helps prevent potential immunological complications in both transfusion and pregnancy situations.

The other options, while related to blood testing, do not focus specifically on the nuance of weak D testing and its implications for anti-D immunoprophylaxis. Compatibility testing ensures safe transfusions but is a broader concept, while identifying blood types and antibodies is part of a more comprehensive blood typing process. Detecting the Rh factor in new blood samples is important but does not specifically address the unique concerns surrounding weak D individuals in relation to anti-D