Question

A 55-year-old male went to his physician complaining of feeling tired and run down.   Two months previously, he had pneumonia and was concerned that he might not have completely recovered.   He indicated that his symptoms only become noticeable if he goes out in the cold. A CBC was performed, showing that his WBC count was normal, his RBC count was just below normal.   A DAT performed on RBC's was weakly positive after incubating at room temperature for 5 minutes.   When the DAT was repeated with monospecific reagents, the tube with anti-C3d was the only one positive.

A) What does a positive DAT indicate? (5)

B) What is the most likely class of the antibody causing the reaction? (5)

C) Why was the DAT positive with anti-C3d when monospecific reagents were used?   (5)

Answer 1

A) positive DAT test indicates antibodies are bound to RBCs means there is presence of hemolysis which is caused by antibodies attached to RBCs. Example like in autoimmune hemolytic anemia, ABO blood group typing, transfusion incompatibility.

B) The most probably antibody causing this reaction is --IgG ( immunoglobulin G) . There is also reaction can be seen in complement C3.

C)DAT positive with anti c3d when monospecific reagent used-- because in monospecific test three tubes are taken for specifically identifying the type of agglutination caused for wheather it is for immunoglobulin antibody or complement components.

Here previously the DAT test indicates that weekly positive ..for confirmation of positive result the monospecific reagent test was done and interpretation ckmes out that anti C3d tube was positive which means the agglutination is due to complement C3.