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If a patient had a positive direct antiglobulin test (DAT) with Anti-IgG, what would happen if you performed a Weak D test on the patient cells?

a-A false-positive result
b-A false-negative result
c-An indeterminate result
d-A valid test result
e-An invalid Rh control test

User HarryM
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1 Answer

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Final answer:

A positive DAT with Anti-IgG can lead to a false-positive result in a Weak D test because the Anti-IgG bound to the red blood cells may cause agglutination, interfering with accurate RhD antigen detection.

Step-by-step explanation:

If a patient has a positive direct antiglobulin test (DAT) with Anti-IgG, performing a Weak D test on the patient's cells can potentially yield a false-positive result. The DAT indicates the presence of anti-immunoglobulin antibodies bound to the red blood cells' surface in vivo. The Weak D test is used to detect a weak expression of the D antigen in the Rh blood group system. However, the presence of Anti-IgG coating the red blood cells in the DAT may cause agglutination in the Weak D test, leading to a false-positive result for RhD antigen presence.

The DAT is used to detect conditions such as autoimmune hemolytic anemia, hemolytic disease of the newborn, or reactions following a blood transfusion. In this test, anti-human globulin reagent is added to the patient's red blood cells, which will agglutinate if antibodies or complement are present on the cells' surface. On the other hand, the Weak D test identifies the weaker expression of the D antigen, which may not be detected by standard Rh typing methods, and it is important for correctly classifying RhD status and preventing Rh incompatibility in blood transfusions.

When a Weak D test is inadvertently performed on red blood cells already coated with Anti-IgG, it can give a false-positive result. This interference occurs because the test will detect the agglutination caused by the bound antibodies rather than the D antigen itself, making the test result unreliable for RhD antigen detection.

User Bi Li
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